Wyoming State Water Plan, Wyoming Water Development Office
Rafting on Snake River Lake Marie, Snowy Mountains Wyoming Wind River Range picture

TECHNICAL MEMORANDUM


SUBJECT: Snake/Salt River Basin Plan
Available Groundwater Determination
PREPARED BY:       Hinckley Consulting
DATE: September 10, 2003

Table of Contents

Introduction and Report Organization
Previous Studies
1964 - Wyoming Water Resources Inventory
1967 - Wyoming Water Planning Program
1975, 1976 - USGS Hydrologic Atlas
1981 - WRRI Basin Studies
1995/96 - USGS County Series
1999 - Teton County Water Supply Master Plan
Other Relevant Reports
Hydrogeology
Stratigraphy and Structure
Quaternary-age Deposits
Tertiary-age Deposits
Older Bedrock Units
Groundwater Circulation
Groundwater Development
Geology
Use Trends
Groundwater Levels
Groundwater Quality
Analytical Data
Groundwater Contamination
Geothermal Resources
Occurrence
Development
Groundwater Availability
Research Resources
Wyoming State Engineer’s Office (WSEO)
United States Geological Survey (USGS)
Wyoming Water Development Commission Groundwater Studies
Wyoming Groundwater Vulnerability Study
Wyoming Department of Environmental Quality (DEQ) - Subdivision Application Review Program
Jackson Hole Environmental Restoration Study
Geologic Mapping
Bibliography
Appendix A - Figures
Appendix B - Lithologic and Water-Bearing Characteristics of Geologic Units in the Snake/Salt River Basin
Appendix C - WSEO Snake/Salt River Basin Permits (electronic format only)
Appendix D - USGS Snake/Salt River Basin Wells (electronic format only)

List of Tables

Table 1 - Municipal Groundwater Use in the Lincoln County Portion of the Snake/Salt River Basin - 1993
Table 2 - Groundwater Consumption in the Snake/Salt River Basin - 2002
Table 3 - Snake/Salt River Basin Groundwater Permit Summary
Table 4 - Snake/Salt River Basin Groundwater Permit Summary - Teton and Lincoln Counties
Table 5 - Generalized Groundwater Quality (mg/l) - Snake/Salt River Basin
Table 6 - Groundwater Quality Standards


Introduction and Report Organization

This memorandum presents an investigation of the groundwater resources of the Snake/Salt River basin. It is one component of a comprehensive review of the water resources of the basin, completed as part of the River Basin Planning Program under the direction of the Wyoming Water Development Commission. As of this writing, similar groundwater memoranda have been completed for the Bear, Green, Powder/Tongue/ and Northeast Wyoming River basins as part of their respective Planning Program reports. We have followed the lead of our predecessors in terms of the general coverage and data compiled to inform future planning with respect to groundwater resources, while adapting to the specific circumstances of the Snake/Salt River basin and adding additional materials as we thought useful.

The text of this memorandum provides general descriptions, summaries, and conclusions. The detailed data upon which these discussions are based are largely contained in the data tables and GIS products attached to the memorandum in its electronic form. We assume that future planners will primarily be addressing individual projects, for which the general discussions will provide reconnaissance-level guidance, but for which the more detailed data will likely be necessary to address unique, site-specific issues.

This is by no means the first basin-wide review of groundwater resources in the Snake/Salt River basin. A history and summary results of previous investigations follows this introduction. Much of the material compiled in this report is drawn directly from previous studies, updated as appropriate for the intervening years, and we fully acknowledge the quality and contribution of those works.

Following the review of previous investigations, we describe the geologic setting and hydrostratigraphy (the groundwater-bearing units beneath the surface) of the Snake/Salt River basin, then present a discussion of groundwater circulation within the basin. A discussion of groundwater quality, including considerations for the protection of groundwater supplies, completes the overview of the groundwater resource.

The past and present level of groundwater development is reviewed, along with trends in groundwater use and changes over time in groundwater levels. The availability of groundwater for future development is also evaluated.

The last two sections of the memorandum introduce the research tools developed for this project and the accompanying detailed datasets, and present a comprehensive bibliography of the literature pertinent to groundwater resources investigations in the Snake/Salt River basin.

All report figures are included in Appendix A. Appendix B is a detailed table of lithologic and water-bearing characteristics of geologic units in the Snake/Salt River. Three other tables have been compiled in Microsoft Excel electronic spreadsheet form only, due to the size of the tables. The first of these three tables is Appendix C, a tabulation of 5,148 Wyoming State Engineer’s Office groundwater right permits as of the most recent postings to their electronic database (May 29, 2002). The other two tables are in Appendix D and are a compilation of data from the USGS. The first spreadsheet in Appendix D, “general”, contains general information, e.g. use, static water level, discharge rate (gpm), etc., for 1,715 groundwater sites monitored by the USGS. The second spreadsheet in Appendix D, “chemistry”, contains data from chemical analyses for 894 wells. USGS groundwater data are current through August 30, 2002, although most of these data were collected under specific research programs of only a few years’ duration.

Previous Studies

This section presents a summary of the key publications addressing the groundwater resources of the Snake/Salt River basin. Relevant historical data (e.g. groundwater use estimates) are summarized here and these reports have contributed extensively to the data compilations detailed in later sections. The scope of our presentation is insufficient to duplicate all the information contained in previous reports, however. Those interested in specific aspects of the Snake/Salt River basin groundwater resource are encouraged to review these original documents as appropriate. Similarly, only previous investigations of a regional nature are presented, i.e. the antecedents for the present memorandum. An extensive bibliography is included as a final section of this memorandum to cover the extensive related literature of a more site- and topic-specific nature.

1964 - Wyoming Water Resources Inventory

This program produced a report for each of Wyoming’s administrative Water Divisions. In the opinion of the Wyoming State Engineer at the time, “the broad picture on use and availability of water in Wyoming is probably more accurately reflected herein than in any previous publication” (p. ii). The Snake/Salt River basin was included in the report for Water Division Number 4 (Smith, 1965).

Data deficiencies were identified throughout Wyoming by these reports, e.g. “Determinations of total irrigated acreage within some drainages indicate that there is a wide divergence between the figures used by various government agencies, the official records showing adjudicated water rights, and the evidence on the ground or as reflected on aerial photographs.” (p. ii).

The groundwater section of the report for the Snake/Salt River basin reads, in its entirety:

“Underground water at the present time is largely restricted to rural domestic and stock watering use. Only seven wells have been filed at the present time in the Snake River Drainage. For the limited information available on ground water, the following general observations are made.

Water, adequate in quantity and quality for domestic or stock use, can generally be obtained from the alluvium along the stream channels. The alluvium deposits in the Salt River Valley and Jackson Hole apparently offer the best ground water potential for irrigation purposes, but the extent of these deposits are not known.

Existing information indicates that the available ground water supply is adequate for irrigation but local contamination from hot springs can be expected in some localities.

A tabulation of filings on completed water wells in the Snake River Drainage in Wyoming follows:”

This text was followed by a listing of the 7 wells: 2 irrigation wells in the Snake River drainage yielding a total of 130 gpm and irrigating 11 original-supply acres; 2 irrigation wells in the Salt River drainage yielding a total of 850 gpm and irrigating 88 “supplemental supply” acres; 2 municipal wells the Snake River drainage yielding a total of 1,694 gpm; and 1 municipal well the Salt River drainage yielding 300 gpm.

1967 - Wyoming Water Planning Program

The Wyoming Water Planning Program was established within the Wyoming State Engineer’s Office by authorization of the Wyoming Legislature in 1967. That program conducted six years of detailed study of Wyoming water resources. “Water & Related Land Resources of the Snake River Basin, Wyoming” was published in 1972 as Wyoming Water Planning Report No. 12. A statewide summary of this report series formed the backbone of the May, 1973 “Wyoming Framework Water Plan”. The reports generated under this program examined, at various levels, all aspects of Wyoming water resources, including, for each river basin, a comprehensive inventory of irrigated lands; compilation of hydrographic data: streamflow, climate, consumptive use, groundwater development, water rights, water quality; and compilation of socio-economic data: population, land-ownership, income.

The lithology of 103 individual geologic units is presented in Report No. 12 along with a qualitative ranking (“not normally an aquifer”, “poor”, “fair”, “good”) of “groundwater potential”, primarily based on physical characteristics and productivity elsewhere in Wyoming rather than direct experience in the Snake/Salt River basin). The only units ranked “good” were:

Bacon Ridge sandstone
Bivouac Fm.
Harebell Fm.
Unconsolidated sediments (i.e. primarily alluvium)

Quantitative data were compiled only for the “sand and gravel (unconsolidated)” aquifer:

Depth Range of Wells (ft)10-100+
Anticipated Well Yields (gpm)
 
common range20-250
 
high range500-1,500+

Total Dissolved Solids (mg/l)20-600

No significant aquifer other than the surface, alluvial aquifer was identified for the Snake/Salt River basin.

The volume of saturated alluvium in the basin was estimated to be 9 million acre-ft. An estimated specific yield of 20% led to the conclusion that approximately 1.8 million acre-ft of groundwater was “available to wells” from aquifer storage. “The annual or regulatory volume that might be withdrawn would be limited to the approximate amount of annual recharge to the alluvial aquifers” (p. 43), estimated to be on the order of 400,000 acre-ft per year for the Snake/Salt River basin (including Grand Teton National Park).

Natural seasonal recharge was described as “great” and general groundwater circulation was described as “rapid” in the alluvial aquifer of the Snake/Salt River basin, with seasonal fluctuations in groundwater levels of 20 to 50 feet in some wells.

Total annual groundwater consumptive use within the basin was estimated to be relatively small:

Irrigation - 680 acre-ft (irrigating 332 acres as a sole source and another 727 acres as a additional source)

Municipal, Domestic, and Stock - 1,430 acre-ft (supplying approximately 75% of the basin population

Industrial - (not significant)

Looking to the future, the 1973 Framework Water Plan concluded, with respect to Snake/Salt River basin groundwater supplies (p. 236):

“Groundwater resources in the alluvium of the major streams are of such magnitude that supplies should be more than adequate for future municipal, domestic, and stock uses. Groundwater supplies are adequate for expanding irrigation locally, for supplementing surface water supplies, and perhaps for completely replacing surface water supplies in some instances.”

The only potential groundwater development project identified was as an alternative supply for a 1,200-acre project to irrigate lands north of the Snake River near Alpine. This project was never developed.

1975, 1976 - USGS Hydrologic Atlas

The Snake/Salt River basin is covered by two publications in the USGS Hydrologic Atlas series:

HA-558, Water Resources of Northwestern Wyoming (Cox, 1976), covering Yellowstone National Park and most of the Snake/Salt River basin above Hoback Junction.

HA-539, Water Resources of the Thrust Belt of Western Wyoming (Lines and Glass, 1975), covering the western Green River basin, most of the Bear River basin and the Snake/Salt River basin south of Jackson.

These reports are basically compilations of hydrologic data, both surface and groundwater, without the planning components (e.g. use, water rights, projections) of the studies described above. (Discussions of water use/consumption in the Snake/Salt River basin are simply repeated from the earlier State of Wyoming reports.) All information is effectively exhibited on 3 large plates in each report, using color graphics, data tables, and minimal narrative.

HA-558 presents completion information, depths-to-water, and pump test data for 51 wells in the northern Snake/Salt River basin, along with an identified geologic source for each. These data allowed plotting a potentiometric surface and calculation of the thickness of saturated aquifer material (for the unconsolidated, surficial aquifer only). Groundwater flow was projected to be towards or sub-parallel with streams across most of the area, although losing reaches (i.e. flow out of the stream into the aquifer) are indicated along Pilgrim Creek (north of Jackson Lake), Cottonwood Creek (south of Jenny Lake), Ditch Creek (12 miles NNE of Jackson), and along Flat Creek upstream of the Elk Refuge.

Streamflow measurements found the following net exchange with groundwater over select, autumn periods (September and October) when streamflows were relatively steady:

Pilgrim Creek (north tributary to Jackson Lake): 2 - 5 cfs loss

Cottonwood Creek (south from Jenny Lake): 11 - 25 cfs loss

Flat Creek (above the Elk Refuge through Jackson): 40 - 45 cfs gain (despite the losing reach noted above)

Snake River (Jackson Lake Dam to Spread Creek): 0 cfs exchange with groundwater

Snake River (5 sites from Spread Creek to Flat Creek): 100 - 290 cfs gains

Not surprisingly, the authors of this study focused their discussion of groundwater development potential on the highly productive alluvial aquifer along the Snake River and its tributaries. A transmissivity on the order of 200,000 gpd/ft was estimated based on gradient and thickness calculations, and it was suggested that wells producing in excess of 1,000 gpm could be developed across much of this aquifer with drawdowns on the order of 10 feet.

Geologic sources are linked with basic water chemistry for 26 wells and 11 springs in the northern Snake/Salt River basin, providing a sampling of data across the geologic column. Hard water with calcium bicarbonate dominant is most common across the study area, although locally significant exceptions were encountered.

HA-539 presents the geologic column for the southern part of the Snake/Salt River basin in 8 “Hydrogeologic Divisions”, based on similar groundwater-bearing characteristics. Lithologic descriptions, thickness maps, and discussions of the availability and chemical quality of groundwater are presented for each division. As above, the chemistry of groundwater in the southern portion of the Snake/Salt River basin was also documented to be dominated by hard, calcium bicarbonate types.

Rather than specific gage data on stream gains from or losses to groundwater, the authors mapped the occurrence of three general conditions (map reproduced below as Figure 1):

Area in which there is little or no groundwater contribution to streamflow - most of the upland portions of the Snake/Salt River basin;

Area in which there is a significant groundwater contribution to streamflow - virtually all the lands of gentler topography along the rivers and streams of the Snake/Salt River basin; and

Areas in which there is a large groundwater contribution to streamflow from a few springs - localized tracts along 1) the mountain front on the north side of the Snake River east of Alpine; 2) most of the larger east-bank tributaries of the Salt River south of Thayne; and 3) Sheep Creek (east-bank tributary of the Greys River) and the upper Greys River.

The first of these conditions likely corresponds with areas of losing streamflow, where surface runoff infiltrates to recharge groundwater. In general, the convergence of groundwater on the stream system throughout the non-mountain portions of the Snake/Salt River basin was identified by these studies, although, particularly, in the Salt River area, the authors suggest highly complicated groundwater circulation patterns in the upland, bedrock aquifers. (See Figure 2.)

A specific example of groundwater flow between surface topographic basins is evaluated for “Periodic Spring” (on Swift Creek upstream of Afton) where the flow of the spring far exceeds what could be recharged within the local basin. This is reflected in the surface discharge of Swift Creek, which averages 3.17 cfs per mi2 of surface drainage area, in contrast to 0.76 cfs/mi2 for the Salt River above Smoot and 1.43 cfs/mi2 for the Greys River at Alpine.

1981 - WRRI Basin Studies

Under US EPA funding, the Water Resources Research Institute of the University of Wyoming undertook an extensive compilation of groundwater data for each of the basins of Wyoming in the late 1970's. Volume V of that series, “Occurrence and Characteristics of Ground Water in the Green River Basin and Overthrust Belt, Wyoming” (Ahern et. al, 1981), included the Snake/Salt River basin. Due to the substantial differences in hydrogeology between the Green and the Snake/Salt River basin, much of the report is written with separate discussions of each area.

The WRRI series include basic information on demographics, land ownership and groundwater use. Approximately 3,500 acres were estimated to receive groundwater irrigation in 1980, primarily in the Star Valley region (Salt River basin). This acreage was estimated to be supplied by approximately 6,000 acre-ft of groundwater withdrawal, of which approximately 4,000 acre-ft were consumed1. The authors used 1978 EPA data to estimate municipal groundwater use: 2,692 acre-ft/yr average production, from 10 spring systems and 4 wells or wellfields. This total was dominated by the Town of Jackson, which was estimated to pump an average of 1,569 acre-ft/yr. (Ahern et al, p. 40). Applying a “rule-of-thumb” value of 50% consumptive use, total municipal consumption of groundwater on the order of 1,500 acre-ft/year is suggested.

The great majority of the WRRI reports is devoted to a physical descriptions and historical data on groundwater occurrence. For the Snake/Salt River basin, the authors adopted an approach similar to the earlier USGS studies in classifying the geologic column into composite “water-bearing zones”. The two classification schemes generally correspond, with the WRRI study differences due largely to inclusion of the Green River basin and their focus on individual formations in some cases.

Extensive data tables and large-format plots present data on aquifer properties, well yields, depths-to-water, and groundwater chemistry. Much of those data is re-compiled or summarized below, but the reader is referred to the WRRI report for extensive narrative discussion.

1995/96 - USGS County Series

As two in a “series of reports describing the water resources of selected Wyoming counties”, the USGS has evaluated “the general occurrence, availability, and chemical quality of surface and groundwater” (Miller et. al, 1996; p. 2) in:

Water Resources of Teton County, Wyoming (USGS Water-Resources Investigations Report 95-4204; Nolan and Miller, 1995); and

Water Resources of Lincoln County, Wyoming (USGS Water-Resources Investigations Report 96-4246; Miller et. al, 1996).

Like the WWPP, USGS, and WRRI reports reviewed above, these two reports summarize the hydrogeology of the respective counties and present extensive data on the occurrence of groundwater. Reflecting the increased concerns with groundwater quality that have evolved over time, additional emphasis (and original sampling / analysis) is placed on organic compounds in groundwater. Also, groundwater levels were monitored in more detail than previously for these reports, providing a better understanding of local groundwater flow directions and gradients. These data are included in the compilations presented below.

1999 - Teton County Water Supply Master Plan

This report was funded by the Wyoming Water Development Commission (WWDC). It addresses community water supplies, including a detailed inventory of sources and of production, transmission, and storage facilities throughout the county. In terms of groundwater resources, the report includes information aquifer properties, groundwater circulation patterns, and groundwater quality, and discussion of groundwater contamination and wellhead protection issues. Ten specific communities/areas2received more detailed investigation of water needs, infrastructure and the site-specific groundwater resources available to meet those needs. The report concludes with a discussion of water-supply system financing in Teton County and estimates of the costs of construction for future water-supply systems.

This was the first of the studies of Snake/Salt River basin groundwater resources to be published in electronic format and to include Geographic Information System (GIS) coverage. The report and related data are available from the WWDC on CD; GIS information is provided in both MapInfo and ArcView formats.

The basic conclusion of the Teton County Water Supply Master Plan with respect to future water supplies for domestic and community use was (p. 172):

Groundwater of adequate quantity and quality is available in most areas where higher density future growth is anticipated in Teton County, limiting the potential for large regional systems even with anticipated increased development, and largely precluding the need to consider surface-based water supplies.

Other Relevant Reports

Related reports include “Estimated Use of Water in Lincoln County, Wyoming, 1993" (USGS Water-Resources Investigations Report 96-4162; Ogle et al, 1996) and “Water Quality in the Upper Snake River Basin” (USGS Circular 1160; Clark et al, 1998). The former report provides the 1993 municipal groundwater use estimates shown in Table 1.

USGS Circular 1160 was produced from the USGS National Water-Quality Assessment (NAWQA) Program. It covered the Snake River basin upstream of central Idaho (approximately Twin Falls), i.e. a much larger area than Wyoming’s Snake/Salt River basin, but provides specific conclusions for the “Jackson Valley”. These conclusions are based on sampling 20 wells from Jackson Lake to Hoback Junction for major ions, 87 pesticides, volatile organic compounds, and radon. Comparisons are with respect to all NAWQA program sites, nationwide, covering approximately 50% of the United States.

- Radon
between median and 75th percentile (radon is naturally occurring,
probably related to the occurrence of volcanic rocks in the area)
- Nitrate
between 25th and median
- Pesticides
less than 25th percentile
- Dissolved Solids
less than 25th percentile
- Volatile Organics
between 25th and median (probably skewed due to sampling of well
near landfill)

Overall, this study concluded that “the quality of ground water in the Jackson Valley area is some of the highest quality ground water reported in the NAWQA Study Units.” (Clark et al., 1998; p. 23).

Table 1 - Municipal Groundwater Use1 in the Lincoln County Portion of the Snake/Salt River
Basin - 1993
Water SupplySourceEstimate Use
(acre-ft/yr)2
Estimated Percent of Use
DomesticCommercialIndustrial
Aftonspring1,6899055
Alpinewells20367330
Thaynesprings1698020
Star Valley
Ranches
springs1,44310000
Star Valley
misc.3
springs and
wells
1,283


TOTAL
4,787


Notes:
1Ogle et al. (1996) is a compilation of “use”, i.e. diversions or withdrawals, rather than
consumption. The latter is typically less, commonly 50% or less, than the former.
2converted to acre-ft from millions of gallons in original table;
3Etna, Freedom, Grover, Osmond, Fairview, Smoot

Hydrogeology

The Snake/Salt River basin has the most complex geology of any basin in Wyoming. The basin shares with the rest of Wyoming the typical configuration of early Cenozoic-age folding and faulting controlling the depth and fracturing of bedrock, with the accumulation of relatively permeable Quaternary-age deposits along stream systems. Superimposed on this geology, however, are the volcanic and glacial deposits associated with the Yellowstone / Absaroka area in the north and the large-scale, low angle thrust faulting of the Overthrust Belt in the south. Figure 3 provides an overview of the areal distribution of the geologic units of the Snake/Salt River basin, aggregated from the more detailed mapping by (Love and Christiansen, 1985).

The reader is referred to the bibliography for more detailed geologic mapping of specific areas. For example, the geologic map included with HA-539 is an excellent, mid-scale (1:250,000) map for the portion of the Snake/Salt River basin south of Jackson.

This section provides a detailed review of the stratigraphy – the basic geologic layers – of the Snake/Salt River basin and an overview of the structure – the orientation, folding, and faulting of rocks. Both are critical to the successful development of groundwater in many of the bedrock aquifers, but it is difficult to usefully generalize locally important structural features.

Stratigraphy and Structure

Appendix B (compiled primarily from Eddy-Miller et al, 1996, Table 12 and Nolan and Miller, 1995, Table 4) presents an annotated geologic column for the Snake/Salt River basin. Geologic units are listed in stratigraphic order, i.e. the youngest at the top of the list, with successively older formations “deeper” in the table. Where water-bearing characteristics are similar, geologic strata, formations, and groups have been combined for this table. (Alternative groupings and formation names may appear in studies focused on other aspects of the geology of the area.)

Appendix B is necessarily a generalization of water-bearing characteristics. As the lithologic descriptions indicate, even within a given formation, groundwater production may vary considerably, depending, for example, on the relative proportions of sand, silt, and clay. A fortunately located and optimally constructed well may provide modest groundwater supplies from nearly any of the listed geologic materials.

Particularly for the well-lithified (i.e. hard bedrock) units listed in Appendix B, the presence of fractures, faults and other openings in the rock may be critical to the production of adequate water supplies. Figure 3 includes an overview of mapped faults in the Snake/Salt River basin (from Lines & Glass, 1975 and Cox, 1976). The critical assessment of these faults, geologic folds, and smaller-scale, local structural features will commonly be an important part of any successful groundwater development project in the bedrock aquifers.

Quaternary-age Deposits. The most productive aquifer in the Snake/Salt River basin is formed by the thick alluvial deposits along the Snake River. Similarly productive materials, but of lesser thickness, occur along most rivers and streams of the study area. These are the sands, gravels, silts, and clays deposited relatively recently (geologically). (The Quaternary is the most recent geologic period.) Because of the major importance of alluvial aquifers in the study area, and the particularly productive nature of these deposits along the Snake River west of Jackson, Figure 3 includes a subdivision termed the “Main Snake River Aquifer”. Outside of the latter deposits, the alluvial materials are of more variable, and commonly lesser, permeability and thickness.

In the South Park area (from Jackson and Wilson to the narrowing of the valley 7 miles south), Love and Albee (1972) described the main aquifer: “Valley and stream deposits of gravel with lesser amounts of sand, silt, and clay. Surface is gravel underlain by thin discontinuous deposits of sand and silt.” They mapped the remaining Quaternary alluvial deposits as “Flood-plain deposits; sand, silt, clay, and minor lenses of gravel; lesser amount of gravel at surface distinguishes these deposits.” Nolan and Miller (1995) term the alluvial deposits occupying the main Snake River floodplain the “Jackson Aquifer” and provide geophysical evidence (Nolan et al., 1998) indicating the aquifer is between 380 feet (Antelope Flats area) and 2,400 feet (Potholes area) thick.

Water-well experience appears to bear out delineation of the Snake River alluvial aquifer within the larger body of Quaternary alluvial deposits. While prolific wells (transmissivities as high as 900,000 gpd/ft) are relatively common in the principal Snake River alluvial aquifer, wells in other areas of the alluvial aquifer are of more variable productivity and problems with sand production are not uncommon. The tested transmissivities of wells in the Rafter J and Melody Ranch areas (along Flat Creek south of Jackson), for example, are between 15,000 and 60,000 gpd/ft. These are still high-permeability deposits in the context of the surrounding bedrock geology, and are fully adequate for most non-agricultural applications, but are distinctly lower in permeability than in the coarser deposits along the Snake River.

“Other Quaternary Deposits” on Figure 3 consist of a wide variety of glacial drift and outwash, loess, landslide debris and talus, swamp and lake deposits, talus breccia, conglomerate, and volcanic rocks. While these deposits are extraordinarily diverse in terms of their composition, they are grouped together here to reflect a generally lower groundwater production potential than the alluvial deposits discussed above. These deposits are also characterized by extreme heterogeneity. Particularly in deposits of glacial origin, highly-productive lenses of clean gravel may be present alongside dense clays with virtually no water-production potential. Loess deposits tend to be relatively unproductive of groundwater. Talus and landslide deposits, although quite permeable, tend to be relatively shallow and well-drained.

Groundwater development in these non-alluvial deposits is best guided by detailed, site-specific investigations, for which the reader is referred to the bibliography and local experience. For example, the “Quaternary alluvium and colluvium” mapped by Nolan and Miller (1995) beneath the Elk Refuge (northeast of Jackson) and along the west side of West Gros Ventre Butte, are further identified as “swamp deposits”(Love et al, 1992); Love and Albee (1972) have mapped the Quaternary deposits along the east side of Highway 26 south of Jackson as loess. Neither of these deposits is nearly as productive as Quaternary-age material that has benefitted from the winnowing action of active stream deposition.

Tertiary-age Deposits. Bedrock aquifers in the Snake/Salt River basin are mainly exposed in the upland areas. Tertiary-age rocks include volcanic deposits and a variety of conglomerate, sandstone, limestone, and mudstone sedimentary rocks. The productivity of these deposits with respect to groundwater varies locally, as a function of variations in texture, thickness, and fracturing. Successful development of useful water supplies, where possible at all, depends upon careful siting and exploration.

In contrast to the Snake River alluvial aquifer, in many areas of the Salt River basin the alluvium may be of substantial surficial extent (e.g. see Figure 3), but is relatively thin, and successful wells have had to penetrate the underlying Salt Lake Formation. Contrary to the unfavorable descriptions of this formation provided by the USGS (Miller et al, 1996; Table 12), it has demonstrated quite variable water-bearing characteristics, both in terms of quantity and quality. For example, the spring system supplying the Town of Thayne issues from the Salt Lake Formation beneath a veneer of Quaternary-age alluvium. These springs are reported to flow 2,200 gpm, attributed to fracture enhanced permeability (Lines and Glass, 1975). Exploratory drilling west of this location (near the town of Thayne) “encountered no significant water bearing formations”, whereas a 310-ft well nearer the springs was judged to be capable of 1,000 gpm (Forsgren Associates,1991).

Similarly, an exploratory well just west of Freedom encountered unacceptable groundwater quality in the Salt Lake Formation (total dissolved solids >1,000 mg/l), but a second well two miles east of Freedom had good quality and a yield of 650 gpm (Forsgren Associates,1991). Evaluation of Salt Lake Formation wells in the Alpine area found specific capacities (gpm per ft of drawdown) varied from over 10 to under 1 over distances of less than a mile. As with the Thayne springs, much of this was attributed to the influence of fracture systems (Sunrise, 1995).

Older Bedrock Units. Mesozoic-age strata in the Snake/Salt River basin are dominated by thick shale formations. Productive wells have been developed locally from interbedded sandstone and conglomerate strata, but as a general rule these strata are relatively unproductive.

Paleozoic-age rocks consist primarily of thick limestone and sandstone formations. These include the Madison Limestone which is famous for producing high capacity groundwater wells at many Wyoming locations. As with all the other bedrock aquifers, however, the productivity of these strata can be quite site-specific, depending upon local enhancement of permeability through fracturing and variations in composition. Limestone, for example, is virtually impermeable in its native state of deposition. Given the faulting and folding of bedrock in the Snake/Salt River basin, however, and the ability of circulating groundwater to expand permeability through solution, limestone units provide very high groundwater production rates under locally favorable conditions.

Beneath the sedimentary section in the Snake/Salt River basin are the pre-Cambrian-age crystalline rocks that are exposed at the surface in the core of the Teton Range. Primary porosity and permeability (i.e. the capacity of these rocks to hold and transmit water) is virtually zero. Only where the rocks are broken by fractures or faults or when weathering has created a rubble zone where the rocks have been exposed to the surface is there likely to be useful groundwater development potential. Careful site selection has been successful in achieving small yields from these rocks in some areas.

(Except as noted, much of the preceding discussion of aquifer characteristics is modified after Jorgensen et al, 1999.)

Groundwater Circulation

Hydrology textbooks commonly begin with a diagram of the “hydrologic cycle” that shows the constant passage of water between the atmosphere, the surface, and the subsurface. With the exception of the water associated with the original deposition of each geologic unit (termed “connate” water and generally of very poor quality), groundwater resources are a function of recharge from and discharge to the surface. Groundwater aquifers provide a large storage reservoir filled by infiltration of precipitation, snowmelt, and streamflow. Water moves through this “reservoir” as a function of groundwater elevation gradients and is “released” through discharge to springs, streams, and wells and through uptake and evapotranspiration by vegetation from the root zone. Groundwater quality is controlled by the solubility of the minerals with which it comes in contact as it travels from recharge to discharge and by its residence time (how long groundwater has been in contact with soluble geologic materials) in the subsurface. Thus, the surface and groundwater resource is one body of water, moving through the basin at widely different rates, but ultimately dependent upon the same fundamental sources.

As discussed above, groundwater recharge occurs primarily across the upland areas of the Snake/Salt River basin. Figure 1 (from HA-539) presents this general pattern, which is the same in the northern portion of the study area, as evidenced by the losing and gaining reaches of specific streams. This same pattern is expressed by the general distribution of ephemeral/intermittent streams vs. perennial streams. The former are commonly indicative of surface water flow being lost to groundwater; the latter are sustained by the year-round discharge of groundwater to the stream. The 1:100,000-scale and larger-scale maps published by the USGS include distinction of perennial streams.

The direction of groundwater flow is generally a function of topography – recharge takes place in upland areas and discharge takes place to the streams in the valleys. Where sufficient groundwater elevation data have been collected, it is possible to contour the groundwater surface. For the Snake/Salt River basin, this has been done for the main alluvial aquifer in the Jackson area – see Figure 4 – which shows groundwater flow parallel to or converging on the Snake River and its major tributaries3. Groundwater gradients vary from 25 to 75 ft per mile in the alluvial aquifer across this map. A map of the groundwater surface along the Salt or Greys River would show a similar pattern – groundwater flow converging on the stream, with gradients determined by local permeability and recharge rates.

Groundwater flow in the bedrock aquifers of upland areas also generally follows topography, but can be greatly complicated by the contorted orientation of aquifers relative to intervening low-permeability layers, and by the preferential flow pathways created by faults, fractures, and, in the carbonate rocks, solution openings. Figure 2 suggests possible patterns of groundwater circulation in a block of the Snake/Salt River basin in the Wyoming Range. Ahern et al. (1981; plate 3) attempted to contour available groundwater elevation data for several aquifers in the Snake/Salt River basin, but local variations were too great to produce results beyond the generalization that bedrock groundwater moves from the mountains towards the valleys.

Combining the groundwater gradients of Figure 4 with permeability data for the alluvial aquifer, groundwater flow velocities on the order of 9 ft/day are indicated for the main Snake River alluvial aquifer (Jorgensen et al., 1999, p. 47). This is quite high, a reflection of the high permeability and abundant recharge to this aquifer. In the areas with a shallower and finer-grained alluvial aquifer and in bedrock aquifers, groundwater flow velocities are orders of magnitude slower. The time of travel from recharge to discharge of groundwater varies from days to years to decades to centuries to millennia, depending on the permeability, elevations, and distances involved (see Heath, 1983 for a general discussion).

Future studies of groundwater gradients and flow directions are referred to site-specific data (e.g. WSEO and USGS databases) and investigations (see bibliography section) to assess these characteristics for individual groundwater development projects.

Groundwater circulation is also influenced by seasonal and long-term fluctuations in groundwater levels. Figure 5 presents those locations for which groundwater levels have been measured through the USGS monitoring program. In summary:

Total number of sites
308
> 20 individual measurements
13 (mostly from 1997/98 from the Jackson area)
11 - 20 individual measurements
19 (mostly from 1993/94 from Star Valley)
3 - 10 individual measurements
46
2 individual measurements
48
1 individual measurement
214

Those sites for which data have been collected over longer periods of time are most useful in the identification (and discrimination) of long-term and seasonal trends. Unfortunately, there are very few high-quality groundwater level monitoring data from the Snake/Salt River basin over any extended period of time.

The most notable exception is the on-going research being conducted by the Wyoming State Engineer’s Office in cooperation with Teton County in the “Westbank” area (west of the Snake River, west of Jackson) as part of the “Jackson Hole, Wyoming, Environmental Restoration Feasibility Study”. Figure 6 presents the locations of the groundwater monitoring wells involved with this study. Many of these have had continuous water level dataloggers installed since 1995.

Figure 7 presents a typical seasonal groundwater level hydrograph for the Snake River alluvial aquifer. This example is from well TCTA-2, located in 41-117-23cac, of the Westbank study (Teton County, 1999) discussed above. The hydrograph shows the annual rise in groundwater levels accompanying spring runoff (and the initiation of flood irrigation, in this case), followed by a decline to late fall and winter lows. Figure 7 also shows the short-term rise and fall of groundwater levels as individual recharge events are superimposed on the overall annual cycle.

Hydrographs for wells elsewhere in the Snake/Salt River basin, although of shorter duration than Figure 7, show similar, regular seasonal changes in groundwater elevation. Given the relative abundance of recharge for groundwater in the basin and the relatively low level of groundwater development, it is likely that most areas would reflect the general patterns of Figure 7, with the degree of seasonal fluctuation and the timing and intensity of short-term changes governed by the recharge and permeability characteristics of the local aquifer.

Groundwater Development

Geology

The geologic distribution of groundwater development is a function of the location of water demands and the availability of groundwater to meet those demands. Fortunately, in the case of the Snake/Salt River basin, these two factors are in rough coincidence, with the most productive aquifers occurring beneath the areas of highest demand, i.e. across the relatively gentle topography and private-land ownership of the floodplains of the Snake and Salt Rivers.

The Microsoft Excel file, Appendix C, lists all Wyoming State Engineer’s Office groundwater right permits as of the most recent postings to their electronic database (May 29, 2002). These are plotted by use type on Figure 8.

The Microsoft Excel file, Appendix D, containing two spreadsheets, “general” and “chemistry”, lists groundwater sites monitored by the USGS. These are plotted on Figure 9. USGS groundwater data are current through August 30, 2002, although most of these data were collected under specific research programs of only a few years’ duration.

Use Trends

The primary development of groundwater in the Snake/Salt River basin is historically and currently for human consumption and related uses associated with domestic and municipal supplies (including subdivision, commercial, and other uses commonly permitted as “Miscellaneous”). Groundwater supplies the vast majority of these uses – approaching 100%. Although only a tiny proportion of total water use in the basin (approximately 8 % of that estimated for agriculture, see Agricultural Tech Memo), this is arguably the most important water resource, as it directly sustains the human population.

From the companion technical memo, “Future Water Demand Projections”, by BBC Research & Consulting (November 25, 2002), Table 2 has been compiled for the normal-year, most-likely use (“Mid”) scenario. The term “use” appears in many water studies without sufficient distinction between diversions/withdrawals and actual consumption (used up, removed from the local hydrologic system). Table 2 presents estimates of groundwater consumption, with the understanding that actual withdrawals of groundwater necessary to sustain this consumption may be one or more times the listed quantities.

In the northern portion of the Snake/Salt River basin (i.e. the Jackson area), the great majority of this water is drawn from the alluvial aquifer along the Snake River, Flat Creek, and Fish Creek. In Star Valley, springs issuing from bedrock units (e.g. Madison Limestone, Bighorn Dolomite, Thaynes Limestone, and Twin Creek Limestone) along the east flank of the valley are the major source of groundwater developed by public water supplies. The Salt Lake Formation and the alluvial aquifer beneath the valley floor supplies local domestic wells and has seen substantial recent development to augment municipal supplies.

Table 2 - Groundwater Consumption in the Snake/Salt River Basin - 2002
Economic Water-Use SectorConsumption (acre-ft/yr)
Public Water Supplies and Rural Domestic6,581
Industrial48
Agriculturalapprox. 7801
Recreational131
1Compared with 99,000 acres under irrigation in the study area, there are only
603 acres with original-supply groundwater permits.

Table 3 summarizes groundwater permit data for the Snake/Salt River basin. (The data for this and the remainder of this permit-based discussion come from the electronic files of the WSEO, data entry current as of May 29, 2002.) Not surprisingly, domestic use dominates on a permit-count basis. Domestic, municipal, and miscellaneous uses, i.e. those representing human consumption, constitute 86% of the groundwater permits issued.

Table 3 - Snake/Salt River Basin Groundwater Permit Summary
UseCountAverage Yield
(gpm)
Average Well
Depth (ft)
Average Water
Level (ft)
Domestic3,1521710949
Stock198153025
Domestic/Stock326178552
Industrial71109244
Irrigation7136712334
Miscellaneous48016313142
Municipal1869220651
Data from Wyoming State Engineer’s Office files, current as of data entry on 5/29/2002; wells with inactive permit status and with zero yields excluded.

Average well depths and average water levels reflect the relative abundance of developable shallow groundwater in the populated areas of the Snake/Salt River basin. The somewhat deeper average for municipal wells likely reflects the higher production requirements and the financial ability to penetrate more of the aquifer for additional protection from declining water levels and surface contamination.

Table 4 presents a comparison between the north (Teton County, Jackson area) and south (Lincoln County, Star Valley) portions of the Snake/Salt River basin. Groundwater irrigation is a minor use in both counties, but what there is largely confined to Star Valley. The slightly higher proportion of stock and stock/domestic permits in this area may also reflect the difference in agricultural activity. In general, the two areas demonstrate quite similar patterns of groundwater development; therefore, the remainder of this discussion will not distinguish between the two.

Figure 10 presents the temporal trend in groundwater development in the Snake/Salt River basin over the 20th century. From minimal development prior to the 1960's, groundwater permits have grown to over 4,000, with a cumulative permitted yield of 155,000 gpm. While this yield calculates to 250,000 acre-ft per year, the actual use of groundwater is far less. Few wells pump at their full permitted capacity more than a small percentage of the time.

Table 4 - Snake/Salt River Basin Groundwater Permit Summary - Teton and Lincoln Counties
UseTeton County
(North)
Teton
Distribution (%)
Lincoln County
(South)
Lincoln
Distribution (%)
Domestic1,93475.71,01970.5
Stock1024.0795.5
Domestic/Stock1234.818312.7
Industrial30.130.2
Irrigation200.8483.3
Miscellaneous36414.21067.3
Municipal100.480.6
Total2,556
1,446
Data from Wyoming State Engineer’s Office files, current as of data entry on 5/29/2002; wells with inactive permit status and with zero yields excluded.

Figure 11 presents the same data, segregated by use type. As reflected in Table 3, domestic use dominates across all years. The appearance of significant numbers of monitor wells since 1989 reflects an increased consciousness of the importance of groundwater quality and the commensurate development of regulatory and research programs to address these concerns. (See discussion below.)

Figure 12 displays trends in domestic well yield, depth, and depth-to-water. Permit yields have remained relatively stable over time, suggesting the basic demands per unit of development have not changed greatly. Average depths-to-water, while increasing in the late 1960's relative to earlier periods, have remained relatively constant since then, suggesting aquifers have been able to sustain these levels of development. The increase in well depth over time may reflect increased concern with the security of groundwater-based domestic water supply systems, perhaps accompanied by an increase in the financial resources to afford deeper drilling.

Figure 13 displays the distribution of domestic-use well depths, showing the relative rarity of wells over 200 feet deep. The one well at the far right of the diagram is the deepest permitted water well in the study area – a 940-ft deep domestic well between Etna and Freedom with a permit yield of 20 gpm. Based on the location of this well, it appears likely to have penetrated primarily the Salt Lake Formation. Apparently, the considerable depth and modest yield is a function of the widely variable water-bearing characteristics of this mixed-lithology formation. This well highlights the local nature of successful groundwater development in many areas of Star Valley. Without a knowledge of the underlying geologic conditions, it is difficult to generalize usefully about groundwater productivity. Conditions can change quite significantly over relatively small distances.

Figure 14 displays the distribution of domestic-use well permitted yields. Nearly all domestic wells have permitted yields of less than 25 gpm. Because the water demands of domestic uses are small, however, permitted yields cannot be taken as equivalent to the well yields that could be realized under maximum production. Although instantaneous demands may be relatively large, over the course of a day, the water demands of a typical single-family home will seldom average over 2 gpm even in summer4. Considering that much of this water is returned to the aquifer via leachate from on-site wastewater septic systems, the actual consumption of groundwater likely averages less than 1 gpm for most of these wells.

Figures 15 and 16 present the same data for stock wells. The predominance of “depths” less than 10 feet indicates that many of these groundwater permits are not wells, but developed springs. As with the domestic wells, the relatively small wells are more likely a function of demand than of aquifer productivity.

Figures 17 and 18 reflect the much greater water demands for a successful irrigation well. Even so, those demands have generally been met with wells less than 200 feet deep. Irrigation-well yields are rarely in the 600-800 gpm range generally considered necessary for large center-pivot irrigation, suggesting the use of smaller sprinkler and direct discharge systems. The largest-yield irrigation well in the basin has a permitted yield of 2,050 gpm. This is a 98-ft deep well on the Box L Ranch 3 miles north of Jackson. As both the small number of wells and the irrigated acreage (see above) suggest, groundwater is not a large factor in irrigation in the Snake/Salt River basin.

Figures 19 and 20, for “miscellaneous”-use wells, generally mirror the domestic-well patterns. The somewhat greater depths and yields likely reflect the most common use for this use designation – small subdivisions.

Figure 21 shows the temporal distribution of domestic well permits in the Snake/Salt River basin. From minimal groundwater development through the mid-1960's, all areas have experienced strong growth since then. Following a decline in the pace of development in the mid-1980's, there have been 120 - 140 new domestic well permits issued each year throughout the 1990's. By county (within the Snake/Salt River basin) the last decade breaks down as:

Teton County60 - 80 permits per year
Lincoln County45 - 55 permits per year
Sublette County6 - 8 permits per year

The pace of stock, irrigation, and municipal groundwater development has remained relatively constant over the last 30 years, with an average of 6, 2, and 0.4 annual permits, respectively. The most recent permit issued for industrial groundwater use was in 1982. While this suggests no trend towards increased use, future groundwater development in this sector will be dependent upon the types of activity that may develop.

In summary, it is clear that the trend in groundwater development in the Snake/Salt River basin is dominated by additional, individual domestic wells. This trend is expected to continue as rural subdivisions proliferate in both the Jackson and Star Valley areas. Growth on the order of 100 to 150 wells per year is indicated, representing additional groundwater consumption on the order of 100 acre-ft per year.

Municipalities (and subdivisions with sufficient density to warrant central water systems) will continue to add incrementally to water-supply facilities and will almost certainly continue to turn to groundwater. Current trends indicate 1 additional municipal supply well in the basin every couple of years. Consumption of groundwater associated with such wells will track municipal population growth.

Groundwater Levels

As noted above, there are relatively few data that address the issue of long-term changes in groundwater levels. Hydrographs for monitoring wells in the Snake/Salt River basin (see Figure 5) show similar, regular seasonal changes in groundwater elevation as indicated on Figure 7 over several annual cycles, with no overall up or down trend. We are aware of no areas within the Snake/Salt River basin where there has been a sustained change (increase or decrease) in groundwater levels over time.

A far larger set of groundwater level data is available through the initial depths-to-water reported with Statements of Completion filed with the WSEO (see Excel file, Appendix C). These values are inconsistently measured, however, and include no elevation datum, so are more useful to examine general relationships than to calculate specific gradients. Overall, these data suggest greater depths-to-groundwater over time, but this is likely due to development moving into more upland areas rather than a decline in groundwater levels at a given location. Figure 22 shows the geographic progression of domestic groundwater development by decade.

Groundwater Quality

Analytical Data

The primary source of groundwater quality data for the Snake/Salt River basin is the USGS, which has collected and analyzed samples from throughout the basin. Additional, site-specific data are commonly available from individual project reports (e.g. those of the WWDC) and from the files of water system operators. Microsoft Excel file, Appendix D, spreadsheet “chemistry”, presents groundwater chemistry data collected by the USGS. Figure 9 plots the location of USGS sampling sites.

Table 5 summarizes the USGS water chemistry data by geologic unit in terms of total dissolved solids, a general measure of the mineral content of water. The table also lists the major cation and anion for each unit. The individual component concentrations are listed in the spreadsheet “chemistry”.
Table 5 - Generalized Groundwater Quality (mg/l) - Snake/Salt River Basin1
Aquifer Group
(no. of samples)
Qa (alluvium)
(201-514)
Qo (gravel,
pediment and fan
deposits)
(6-12)
Tv (Tertiary
undivided)
(22-48)
Mu (Mesozoic
undivided)
(9-35)
Pv (Paleozoic
undivided)(5-18)

MCL2averagerangeaveragerangeaveragerangeaveragerangeaveragerange
TDS(500)24925-538281149-70723780-548410102-5690223101-829
Hardness
19614-46014115-2401805-3202093-130018789-500
Alkalinity
15216-42720968-47919446-50222289-69921091-622
Calcium
54.44.2-20441.14.7-6752.61.3-8463.11.1-4204924-160
Magnesium
14.290.77-2029.030.69-1711.760.32-2612.700.02-6915.45-28
Sodium
11.80.8-10047.22.1-17014.60.9-22062.61.0-14006.60-91
Potassium
1.810.40-171.30.3-2.41.60.4-45.350.2-1502.00.2-25
Sulfate(250)29.90.4-17019.05-5410.30.3-2261.22.4-130016.41.3-120
Chloride(250)11.60.2-15016.10.4-912.60.5-4.259.7<0.1-19007.2<0.1-100
Fluoride4.00.30-3.60.5<0.1-1.90.3<0.1-1.60.60-8.20.20-0.5
Silica
12.82.1-48159-519.45.3-4311.15.7-408.72.8-39
Nitrates101.200.01-152.07<0.05-7.50.12<0.05-0.480.73<0.05-9.700.29<0.05-0.81
Phosphorus
0.10<0.01-2.540.02<0.01-0.060.02<0.01-0.120.02<0.01-0.060.01<0.01-0.02
Notes: Data summarized from USGS Database (8/30/02)
1complete data are provided in Appendix D, Microsoft Excel file, spreadsheet “chemistry”
2values in parentheses are secondary standards

These samples do not represent a concerted effort to obtain representative groundwater analyses for each unit. Rather, they come from existing wells to which the USGS had access or from special studies done to investigate specific water-quality issues. The groundwater quality in virtually any unit may vary widely as a function of lithology, residence time, circulation pathways, and input from adjacent units. Most commonly, aquifers are developed at relatively shallow depths (compared to the full depths of occurrence). Thus, these analyses should be considered generally typical of the developed portions of the listed geologic units.

For comparison to the data of Table 5 and Appendix D (spreadsheet “chemistry”), Table 6 presents water-quality standards. These standards define the parameters relevant to human consumption as well as other uses. The EPA Maximum Contaminant Levels (MCL) are based on human health effects and are legally enforceable. The EPA Secondary levels are based on drinking water aesthetics (color, odor, staining) and are advisory only.

In the relatively open hydrogeologic system represented by the alluvial aquifers, recharge is rapid and aquifer residence times are relatively short. Thus, surface-derived water has little opportunity to become seriously mineralized. The analyses reflected in Appendix D, spreadsheet “chemistry”, demonstrate that total dissolved solids (TDS) concentrations are commonly less than 200 mg/l from these deposits and only rarely are above the EPA secondary drinking water standard of 500 mg/l. (Secondary standards are established with reference to color, taste, and general aesthetic quality rather than human health.) Much of the alluvial groundwater is relatively hard, likely the result of the abundance of limestone-derived sands and gravels. Where underlying bedrock formations make substantial contributions to the groundwater, as may occur along the deep faults bordering the east side of Star Valley and Jackson Hole, additional mineralization of groundwater may occur. Trace element and organics analysis of these waters suggests little need for concern, with the possible exception of iron and manganese which may locally exceed secondary drinking water standards.

As with the basic productivity of the bedrock aquifers, groundwater quality is quite variable as well. Due to the generally lower permeabilities and longer times in saturated contact with the rock materials, groundwater tends to be somewhat more mineralized than in the alluvial aquifer, although exceptions are not uncommon. Total dissolved solids concentrations over 300 mg/l are common from the Mesozoic aquifers; Appendix D (spreadsheet “chemistry”) includes one well producing from the Mesozoic-age Bear River Formation with a TDS value over 1,000 mg/l. Trace element analyses demonstrate locally elevated levels of boron, iron, manganese, and zinc, again likely dependent upon site-specific conditions. The range of groundwater chemistry for the bedrock aquifers reflected in spreadsheet “chemistry” demonstrates that many are capable of yielding water supplies of acceptable quality. Site-specific conditions are of most importance in this regard, and those systems drawing groundwater from bedrock formations are the most likely to experience unacceptable concentrations of aquifer minerals. (This discussion was adapted from Jorgensen et al., 1999.)

Groundwater Contamination

Jorgensen et al. (1999) present a detailed discussion of potential groundwater contamination and wellhead protection for the developed portion of Teton County, including relevant groundwater quality standards and land use regulations and tables of groundwater contamination events. The following paragraphs are adapted and generalized from that report.

Table 6 - Groundwater Quality Standards
(All constituent concentrations are in milligrams per liter unless noted otherwise. μg/L, micrograms per liter; mg/L, milligrams per liter; ºC, degrees Celsius; --, no data; ---, no established level)
Constituent or PropertyDomestic UseAgricultural UseLivestock UsePublic Drinking Water Supplies
(Modified from Wyoming Department of Environmental Quality, 1990a, p. 9) Maximum Contaminant LevelSecondary Maximum Contaminant Level
Inorganic
Aluminum (μg/L)--5,0005,000

Arsenic (μg/L)50100200150---
Barium (μg/L)1,000----11,000---
Boron (μg/L)7507505,000

Cadmium (μg/L)10105025---
Chloride2501002,000---3250
Chromium (μg/L)50100502100---
Copper (μg/L)1,000200500---31,000
Fluoride4(1.4-2.4)----24.032.0
Iron (μg/L)3005,000-----3300
Lead (μg/L)505,000100150---
Manganese (μg/L)50200-----350
Mercury (μg/L)2--0.0522---
Nitrate, as nitrogen10----

Nitrite, nitrate + nitrite, as nitrogen----100110---
Selenium (μg/L)102050250---
Silver (μg/L)50-------3100
Sulfate2502003,000---3250
Zinc (μg/L)


---35,000
Dissolved solids5002,0005,000---3500
pH, standard units(6.5-9.0)(4.5-9.0)(6.5-8.5)---36.5-8.5
Sodium-adsorption ratio--8--


Selected Organic
2,4-D


20.07
Silvex


20.05
Endrin


10.0002
Lindane


20.0002
Methoxychlor


20.04
Toxaphene


20.003
1. U.S. Environmental Protection Agency, 1991a
2. U.S. Environmental Protection Agency, 1991b
3. U.S. Environmental Protection Agency, 1991c
4. Dependent on the annual average of the maximum daily air temperature: 1.4 mg/L corresponds with a temperature range of 26.3 to 32.5oC and 2.4 mg/L corresponds with a temperature of 12.0oC and below.

There are two general sources of potential contamination of groundwater supplies in the Snake/Salt River basin:

  1. sources which affect broad areas, typically at relatively low levels and over long time periods. Many of these are known as “non-point” sources and include septic system discharge and applications of agricultural chemicals like fertilizer, herbicides and pesticides.

  2. localized discharges of contaminants, often at high concentrations, but in specific, limited areas. In the Snake/Salt River basin, these are generally limited to accidental spills and discharges. Both types of contamination are addressed under the general subject of wellhead protection – protection from contamination of the area through which groundwater flows to a water-supply well.

Figure 3 depicts the density of domestic water wells in the Snake/Salt River basin by 40-acre tract, based on well registration files of the Wyoming State Engineer’s Office. (Groundwater permits are located only to the 1/4 1/4 Section.) Although aquifer contamination potential is a function of many local variables (e.g. depth-to-groundwater, permeability, aquifer thickness, aquifer lithology), a common “rule-of-thumb” is that domestic septic systems create potentially serious groundwater nitrate contamination problems at lot sizes of 2 acres or less. Assuming that each registered domestic-use well corresponds with a single-residence septic system, Figure 3 provides a general picture of the density of potential nitrate sources. (2-acre lots correspond to 20 or more systems on a 40-acre tract.)

The spacing of individual wastewater septic systems is controlled by setback requirements with respect to water-supply wells and septic systems and, perhaps most importantly, by minimum lot sizes in some areas. As an additional regulatory control on wastewater disposal contamination of groundwater, any subdivisions which have applied for county permitting after July 1, 1997 are subject to Wyoming Statute 18-5-306 which established the Subdivision Application Review Program within the Wyoming Department of Environmental Quality (WDEQ) - Water Quality Division. (See WDEQ, 1998.) Pursuant to this law, WDEQ has prepared guidelines to assess the adequacy of water and wastewater systems for all new subdivisions, and all new subdivisions are required to prepare engineering and hydrogeologic analyses of these systems. The required analysis includes investigation of groundwater contaminant loading by the proposed wastewater disposal system – whether a centralized facility or individual septic tanks and leach fields. The required area of investigation extends beyond the proposed subdivision to include the area through which groundwater will flow over a two-year time period. A site-specific determination “that the proposed lot sizes will not create a density of septic systems such that effluent from septic systems will cause groundwater pollution” is required. Figure 23 presents the location of subdivisions within the Snake/Salt River basin for which wastewater suitability reports have been prepared (based on the files of WDEQ).

The ease with which contamination may enter an aquifer is commonly termed the aquifer “sensitivity”. It is primarily a function of the permeability distribution above and within the aquifer, the depth to groundwater, and the rate of recharge from the surface to the aquifer. As a general statement, the productive aquifers of the Snake/Salt River basin have a relatively high sensitivity to contamination because:

  1. High aquifer permeabilities allow rapid movement of contaminants between points of recharge/infiltration and discharge.
  2. Permeable soils and the absence of low-permeability strata (e.g. confining layers) between the surface the underlying aquifers allow surface contaminants to readily reach groundwater.
  3. Depths to water are relatively small, allowing rapid transmission of surface contaminants to the water table.
  4. Aquifer recharge, particularly in areas subject to irrigation, provides the water to carry contaminants into the groundwater system.

The University of Wyoming has recently completed a statewide assessment of groundwater vulnerability / aquifer sensitivity (Hamerlink and Arneson, 1998) based on general aquifer considerations. Their report includes a useful discussion of aquifer principles associated with sensitivity assessment; county-by-county appendices provide map details.

Figure 24 is the Snake/Salt River basin portion of the depth-to-initial-groundwater maps developed by the University of Wyoming study (received digitally from the University of Wyoming Spatial Data Visualization Center). Input data for this map are the reported static water levels from Statements of Completion filed with the Wyoming State Engineer’s Office, compiled at a resolution of one value per 100 meters square. The shallower the groundwater, the more susceptible it is to contamination simply because contaminants introduced at the surface can more rapidly enter the groundwater system and there is relatively little intervening soil to adsorb contaminants before they reach the groundwater. This is of special importance regarding wastewater disposal through leach fields because an important part of the treatment process takes place in the unsaturated soil above the water table.

Over most of the developed portion of the study area, depths to groundwater are less than approximately 30 feet. Combining with these relatively shallow groundwater depths to increase aquifer sensitivity is the absence of low-permeability layers to impede the progress of a contaminant to and through the aquifer.

Figure 25 presents a composite rating of aquifer sensitivity to contamination from surface sources, as developed by the University of Wyoming project. These ratings take into account generalized data on aquifer permeability, depth to the water table, the nature of the soils and other material above the water table, recharge rates, and land slope. Ratings have no absolute meaning; they simply reflect the relative sensitivity of the aquifer in one location as opposed to another (10 is the most sensitive; 1 is the least sensitive). The area underlain by the main alluvial aquifer along the Snake River has received the highest possible sensitivity rating.

In summary, the developed aquifers of the Snake/Salt River basin are generally susceptible to aquifer contamination. Future planning and development should take this into account through appropriate site selection and design of water-supply wells. In addition, the development of potentially conflicting uses in aquifer recharge areas should be monitored. Given the widespread use of the alluvial aquifer in the Snake/Salt River basin, individual “wellhead protection plans” should be augmented with a general concern for all activities with potential for contamination of groundwater in and around the developable portions of the basin.

Geothermal Resources

For certain applications, the temperature of groundwater may itself be a useful resource. Thermal energy can be usefully extracted from groundwater at temperatures as low as 40oF through the use of groundwater heat pumps, typically used for small space-heating loads. For small-scale, e.g. residential, applications of this level of geothermal energy, little is required beyond a sustainable source of groundwater on the order of a few gallons per minute. At the opposite extreme of geothermal resources are natural occurrences of super-heated steam which can be tapped to drive electrical generators. Such occurrences are quite rare and require special circumstances of heat sources and groundwater circulation. In between are a wide variety of geothermal applications, including spas, swimming pools, commercial space heating, de-icing systems, fish propagation, hydroponics, industrial process heating, district space heating, and generation through the use of binary fluid systems.

Additional general information on geothermal resource applications is available through the U.S. Department of Energy Office of Energy Efficiency and Renewable Energy (EERE) (http://www.eere.energy.gov), the Oregon Institute of Technology Geo-Heat Center (http://geoheat.oit.edu), and the private, non-profit Geothermal Resource Council (http://www.geothermal.org).

As described in a series of reports on Wyoming geothermal resources (e.g. Hinckley and Heasler, 1985) most of the geothermal resources in Wyoming are a function of the deep circulation of groundwater. The natural “plumbing” of an aquifer carries recharge water sufficiently deep to be significantly heated by the normal geothermal gradient of the earth - approximately 14ºF per 1,000 feet of depth. Groundwater circulation (or deep drilling) then brings this water sufficiently close to the surface that it can be economically developed for moderate-temperature, near-source applications. Only in the Yellowstone National Park area are there special subsurface sources of heat that produce very hot groundwater and even super-heated steam.

Occurrence

Heasler et al. (1983) provide an overview of the geothermal resources of Wyoming, including the Snake/Salt River basin. (Their work is the source for the geothermal-resource presentation for this area in the Ground Water Atlas of the United States (USGS, 1996) and for many other similar, survey-level publications.) Although not hosting the extensive, deep sedimentary basin type of geothermal resources that are present elsewhere in Wyoming, the Snake/Salt River basin has a variety of local geothermal features; see Figure 26. These vary from the 64ºF flow of the Teton Valley Warm Springs near Kelly, to 200ºF thermal springs in the Yellowstone Park portion of the basin. Geochemical indicators suggest a subsurface temperature of 270ºF for the Huckleberry Hot Spring system, just south of Yellowstone, but this likely marks the southern extent of the Yellowstone geothermal system that draws its heat from a cooling body of molten rock at depth.

Mitchell et al. (1980) provide a similar, state-wide assessment of geothermal resources in Idaho. Like in the Wyoming portion of the Snake/Salt River basin, they identify scattered features of moderate temperature in adjacent areas of Idaho. Excluding the area immediately west of Yellowstone, the nearest Idaho geothermal system of regional significance is approximately 25 miles west of the Wyoming border in the Blackfoot Reservoir - Grays Lake area.

There is a large body of research dedicated to the geological, geophysical, geochemical, and biological evaluation of the Yellowstone’s world-class geothermal features. Breckenridge and Hinckley (1978) provide an overview of Yellowstone’s geothermal features. Because Yellowstone Park occupies only the northernmost portion of the Snake/Salt River basin and represents little development potential within the basin, its geothermal resources are not presented in detail in this report. However, the U.S. Geological Survey hosts the Yellowstone Volcanic Observatory, the products and research of which may be accessed via http://volcanoes.usgs.gov/yvo/. Washington State University maintains a 10,000-citation database of Scientific Research and Science in Yellowstone National Park at http://www.wsulibs.wsu.edu/yellowstone/. Also, the University of Utah has long had a focus on Yellowstone geological and geothermal studies. Their Yellowstone database, Geophysical and Geological Studies of the Yellowstone Hotspot and the Yellowstone Volcanic System (and Surrounding Area), may be accessed at http://www.mines.utah.edu/~rbsmith/ysref.html [new link 10/2009 HERE]. The interested reader is referred to these sources for additional information.

Breckenridge and Hinckley’s 1978 “Thermal Springs of Wyoming” provides a comprehensive inventory of springs producing water in excess of 50ºF, including chapters on both Teton and Lincoln Counties. South of Yellowstone, geothermal features are generally of lesser temperature and are largely a function of deep groundwater circulation along local fault systems. As depicted on Figure 26, there is no concentration of geothermal features in the Snake/Salt River basin, but isolated occurrences in both valley and upland settings.

The only exception to this generally moderate-grade resource of which we are aware is at the Auburn Hot Springs. This is the only geothermal system in Wyoming outside Yellowstone (and the Huckleberry Hot Springs area immediately south of Yellowstone) where geochemical indicators suggest subsurface temperatures (300ºF) potentially high enough to approach electrical generation potential (Breckenridge and Hinckley, 1978). The surface discharge of this system has a maximum temperature of approximately 140ºF. Such indicators earn the Auburn area special consideration on regional-scale evaluations of geothermal potential, e.g. “Temperature Above 100ºC” on a map of “Geothermal Resources Areas of the United States” (Boyd, 2002); and extension of the “good-excellent” rating of geothermal resources southward from Yellowstone on the map of “United States Geothermal Potential” by the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy (EERE) project “GeoPowering the West” (http://www.eere.energy.gov). Similarly, the communities of Auburn, Grover, and Turnerville are identified as being able to “potentially utilize geothermal energy for district heating and other applications” by virtue of being “within 8 km of a geothermal resource with a temperature of at least 50ºC” in the Oregon Institute of Technology’s 2003 compilation of geothermal resources (http://geoheat.oit.edu/colres.htm).

Development

Due to its location primarily within the national park, the Yellowstone geothermal system has been developed only in terms of its scenic and aesthetic values, and scientific research has been focused on geological and biological processes rather than on the resource’s commercial potential. (Prospecting with regard to exotic, high-temperature microbes may represent an exception.) Elsewhere in the basin, land ownership patterns also impact the potential development of geothermal resources, with several local systems falling within other National Park and National Forest lands. While several of these features host recreational use (e.g. Huckleberry Hot Springs, Granite Hot Springs) and thermal springs at the Jackson Fish Hatchery are used in fish-rearing operations, there is little likelihood of more intense development.

Geothermal features on non-federal and private lands are similarly used primarily simply as attractive sources of warm water for bathing, swimming, soaking, limited low-technology space heating, and, in the case of the Kelly Warm Springs, for kayak practice sessions.

Geothermal deposits of sulphur are reported to have been mined in the late 1940's at the Auburn site. Hinckley and Breckenridge (1977) reported the issuance of Geothermal Resource Permits by the Wyoming Board of Land Commissioners for three tracts in the Auburn-Thayne area and consideration of several tracts just west into Idaho under the federal geothermal leasing program.

Hinckley Consulting was involved in a geothermal development program immediately south of the Auburn Hot Springs in 1996. This project included completion of several flowing geothermal wells and examination of a wide range of applications, including space heating, aquaculture, and binary fluid generation of electricity. To date, no projects in the Auburn area have moved beyond the evaluation stage, nor is there currently active geothermal leasing activity.

Despite the limitations on geothermal development imposed by land ownership patterns in the Snake/Salt River basin, there are scattered occurrences of local geothermal systems with development potential for moderate-temperature applications. If the present understanding of these systems as largely fault controlled is correct, there is potential for increased development through drilling – an improvement in volume, reliability and control over simply taking the natural flow of warm springs. However, that potential is likely localized along the controlling geologic structures and the potential for subsurface temperatures substantially higher than the observed discharge temperatures (rarely >110ºF) is small.

To date, development interest and economics have not justified applications much beyond the obvious pleasures of direct contact with warm water. The most viable candidate for development appears to be the system at Auburn, which is largely located on private lands. However, intermittent exploration interest over many decades has so far been unsuccessful in identifying an economically viable application.

Groundwater Availability

The “availability” of groundwater can be addressed in many ways, from calculation of the total groundwater present or the total usefully recoverable groundwater present beneath a certain area (like a mineral resource), to calculation of the total annual groundwater output of an area (like streamflow), to calculation of the annual volume of groundwater that can be developed without significantly impacting other, existing water-resource users. The last is the most appealing approach, but requires definition of “significant” and determination of which existing uses to consider (domestic, agricultural, environmental, aesthetic). The requirements of mass balance within any physical system ensure that any diversion of groundwater at one point results in an equal diminution of groundwater elsewhere, and that diminution must show up as a decrease in streamflow, evaporation, groundwater outflow from the system, evapotranspiration (crop, non-crop, human, animal), or groundwater storage.

The volume of saturated pore space in the subsurface represents the gross volume of groundwater and is likely on the order of 100's of millions of acre-ft5. Much of this water is of unacceptable quality, is too deep to be economically developable, or is contained in formations from which groundwater cannot be extracted at useful rates (e.g. thick shale units), however, so the usable groundwater resource is vastly smaller than the total groundwater in storage. Considering only the alluvial aquifer (covering approximately 400 mi2) in the Snake/Salt River basin, and assuming an average saturated thickness of 200 feet and an effective porosity of 20%, a volume of 10 million acre-ft of useful groundwater in storage is calculated. Were groundwater a static, nonrenewable resource, like coal, this volume might approximate the developable resource.

Groundwater is a very dynamic resource, however, particularly groundwater of high quality occurring at depths feasible for development. Figure 27 suggests an average annual recharge rate of approximately 4 inches. Across the 4,700 mi2 of the Snake/Salt River basin, this comes to 1 million acre-ft/yr. The base flows of the Salt and Greys rivers (i.e. the streamflow that is sustained by groundwater input through the period of the year without significant precipitation input) suggest average groundwater output of 250 and 350 acre-ft/mi2/yr, respectively. (The Snake River basin below Jackson Lake is not considered due to the impact of reservoir modulation on base flows.) Applying a value of 300 acre-ft/mi2/yr to the entire basin suggests a total groundwater output of 1.5 million acre-ft/yr, roughly comparable to the recharge-based estimate. Of course, development and consumption of this “available” groundwater would leave the streams of the Snake/Salt River basin dry through much of the year.

A more detailed, groundwater-model based mass balance for the alluvial aquifer between Jackson Lake and Hoback Junction was developed by San Juan and Kolm (1996). They estimated a total recharge of approximately 50,000 acre-ft per year, with 25,000 acre-ft per year of groundwater discharge through evapotranspiration and 25,000 acre-ft per year of discharge to streams.

In any case, the current level of groundwater consumption estimated for the basin (Table 2, above) is a small fraction of the annual groundwater budget. As discussed above, there is little indication of widespread reductions in groundwater levels in the study area, although long-term data are sparse. Streamflow depletions due to groundwater development have almost certainly occurred, but are of a magnitude to be largely imperceptible given the general abundance of streamflow in the basin. At a basin-wide level, groundwater remains an abundant resource which, properly managed, should be capable of sustaining the trends identified above well into the future.

The preceding paragraphs establish the general scale of the groundwater resource for the Snake/Salt River basin, but, as a practical matter, the availability of groundwater is a local and project-specific function of competing uses, water quality needs, economics, and legal constraints, overlain upon the basic characteristics of aquifer properties and groundwater quality discussed in detail above. The information contained in this report (and its associated electronic databases and GIS products) is provided to inform site-specific evaluations of groundwater availability. General, summary conclusions by aquifer group are provided below.

The availability of groundwater from the Snake River alluvial deposits in central Teton County is primarily limited only by the ability of the Snake River (3 million acre-ft per year) to provide recharge. Aquifer permeability is sufficient, in most areas, to support production rates on the order of 1,000 gpm from individual wells. It is unlikely that groundwater development from this aquifer will impact surface flows sufficiently to trigger concerns about consumption of the volume of the combined water resource over any reasonable planning horizon. “Local water supplies are, in most cases, readily available through groundwater development. While each water supply system presents unique hydrogeologic and engineering concerns, the need for long-distance conveyance of water from areas of supply to areas of use is relatively unlikely” (Jorgensen et al., 1999). A more likely constraint on groundwater development in this area is the incremental deterioration of groundwater quality that accompanies the establishment of increasing concentrations of domestic, municipal, commercial, and other uses.

In Star Valley, the alluvial deposits are of much less thickness than along the Snake River and are above the groundwater table in many areas. Successful well development across the valley floor has been primarily based on the highly variable Salt Lake Formation. Development experience with this formation demonstrates that high-volume wells are possible, but that careful, site-specific exploration is necessary and that groundwater of adequate quantity and quality may not be available at all sites.

Alluvial deposits are also present along many tributary streams (e.g. Hoback, Greys, Gros Ventre, Buffalo Fork Rivers) in the basin, but are generally of such limited extent and so closely tied to surface water that they likely provide useful groundwater development opportunities only under special, locally-favorable conditions.

Springs issuing from bedrock units on the east side of Star Valley have been extensively developed and, with adequate safeguards with respect to water quality, can be expected to continue to produce indefinitely. In many cases, properly sited and completed wells may be successful in tapping these same groundwater sources in a more controllable manner, providing the ability to temporarily overdraft the aquifer in times of need and superior protection from surface-based contaminants.

Bedrock aquifers in the upland areas of the Snake/Salt River basin provide a full spectrum of groundwater development potential, from low permeability and low water quality to highly productive aquifers with good water quality. Due to the complexities of the area bedrock geology, these conditions are quite site-specific and can change dramatically over short distances. Although the sandstone and carbonate (limestone and dolomite) units generally produce the most favorable environment for local, fracture enhancement of permeability, detailed, site-specific evaluations and exploratory drilling should be anticipated in areas where groundwater is sought from these units.

Research Resources

This section reviews the information sources available for evaluation of groundwater resources in the Snake/Salt River basin. Much of the information compiled from these sources has been implemented through GIS layers accompanying the electronic version of this report.

Only the principal, public sources of information are reviewed here. The bibliography provides much more depth with respect to individual studies. Also, there are many local and private sources of information (well drillers, site-specific studies done for private or local public clients, academic research projects, etc.) that may provide valuable information regarding specific groundwater issues.

Wyoming State Engineer’s Office (WSEO)

Wyoming law requires that any beneficial use of groundwater in the state receive a permit issued by the WSEO. Typically, a Statement of Completion is filed upon completion of a well or spring development. The statement typically includes information on the depth, diameter, casing, screens, lithology, water levels, productivity, pumping equipment and aquifer test results. This information is generally supplied by the owner or driller, so varies considerably in detail and accuracy. For those wells that have been adjudicated (4% of those in the Snake/Salt River basin), the WSEO files contain additional information resulting from a field inspection of the well by WSEO personnel.

The basic WSEO information for each permit issued in the Snake/Salt River basin as of the May 29, 2002 posting to the electronic database has been compiled as a GIS layer for the overall basin planning project. Appendix C tabulates these data; Figure 8 presents the geographic distribution. This does not include well completion, lithology and aquifer test information, for which one must currently inspect the physical files at the WSEO offices in Cheyenne, Wyoming. (Details of individual well completions, lithology, and aquifer testing have been manually extracted from the WSEO files for community water-supply wells in Teton County and included in electronic form with Jorgensen et al., 1999.) The basic groundwater permit information is updated periodically and made available to the public via the WSEO website: http://seo.state.wy.us

United States Geological Survey (USGS)

The USGS maintains a comprehensive database of groundwater data collected over the course of many years of investigations. Unlike the WSEO database, which encompasses nearly every water well in the state, the USGS data are compiled from individual research efforts and vary widely in terms of the specific groundwater characteristics addressed, the duration of the study, and the density of data collection.

The basic USGS groundwater data as of August 30, 2002 have been compiled as a GIS layer for the overall basin planning project. Appendix D (spreadsheets “general” and “chemistry”) tabulates these data. Additional and updated information are available from the USGS website: http://waterdata.usgs.gov/wy/nwis/gwsi [new link 10/2009 HERE].

Wyoming Water Development Commission Groundwater Studies

Through state-sponsored projects and regulatory programs, a variety of valuable groundwater information has been developed. Figure 28 presents location information for relevant Wyoming Water Development Commission (WWDC) reports. These are typically site-specific studies requested by local “sponsors” to solve identified water-supply needs. Those involving groundwater typically include a least a brief review of groundwater resources in the local area, with a primary focus on existing or potential water-supply wells. Many of these studies have involved exploratory drilling, for which detailed lithologic logs and well-documented pump tests are generally required. The appendix and accompanying GIS layer provide the report references for WWDC studies in the Snake/Salt River basin. The reader is referred to those reports for specific information. A complete library of reports is maintained by the WWDC offices in Cheyenne. The Wyoming Water Data System (WRDS) in Laramie has a nearly-complete set. Less-complete collections are available at the University of Wyoming libraries. The individual sponsors may be expected to have WWDC reports locally available. Both the WRDS and University library catalogs are available on-line, at http://www.wrds.uwyo.edu/ and http://www-lib.uwyo.edu/, respectively.

Wyoming Groundwater Vulnerability Study

This program was initiated in 1992 by the Wyoming Department of Environmental Quality (WDEQ). The final reports consist of an overall presentation of the program (Hammerlink and Arneson, 1998), with individual reports for each Wyoming county as appendices: Appendix E-15 (1998) for Lincoln County and Appendix E-15 (1999) for Teton County. The program consisted of 1:100,000-scale compilation of data on:

depth-to-first-aquifer (from WSEO well Statements of Completion),

geohydrologic setting (characterization of mapped geologic units based on lithologies and aquifer taxonomy from previous studies, e.g. the WRRI and USGS studies cited above),

soils (sensitivity rankings based on soil thickness and texture),

aquifer recharge (based on soil characteristics and local precipitation rates),

slope (machine-calculated from USGS Digital Elevation Models (DEM), and

vadose zone (sensitivity rankings based on mapped surficial and bedrock geology).

A GIS was then used to combine the above characteristics into composite scores on “aquifer sensitivity” – the intrinsic ability of the subsurface environment to transport surface contaminants into groundwater, and “groundwater vulnerability” – the integration of aquifer sensitivity with current land use practices likely to cause groundwater contamination. For example, a porous soil overlying a fractured limestone in an area of abundant rainfall is “sensitive” to groundwater contamination. Heavy use of agricultural pesticides in such an area renders it “vulnerable”. Figures 24, 25, and 27 present the results of the Wyoming Ground Water Vulnerability Assessment project for the Snake/Salt River basin. The complete reports are available on CD from the Wyoming Geographic Information Science Center (WYGISC), P.O. Box 4008, Laramie, Wyoming 82071-4008; 307-766-2532; http://www.wygisc.uwyo.edu.

Wyoming Department of Environmental Quality (DEQ) - Subdivision Application Review Program

Since 1997, each subdivision approved in Wyoming has had to evaluate the adequacy of the available or proposed water-supply and wastewater-disposal facilities. These evaluations are reviewed by DEQ and the Wyoming State Engineer’s Office, which maintains a collection of the submitted reports. (These reports are typically completed by consultants for the subdivision proponents.) For those subdivisions in which groundwater is the proposed water supply, these reports typically contain detailed, local evaluations of groundwater characteristics, addressing both the volumetric and quality adequacy of groundwater supplies and the vulnerability of the groundwater supply to contamination from septic systems and other surface sources.

The location of the subdivisions in the Snake/Salt River basin for which DEQ has received reports are shown on Figure 23.

Jackson Hole Environmental Restoration Study

In cooperation with the Teton County Commission, the WSEO has been intensively monitoring groundwater elevations at 50 sites in the Snake River alluvial deposits west of Jackson. This study is discussed briefly above. Although of limited geographic extent, it represents a unique groundwater data resource by virtue of the density and duration of the data collection. The project involves personnel from the Wyoming State Engineer’s Office, Teton County, and the U.S. Bureau of Reclamation. It is being conducted to examine environmental and land use issues along the Snake River west of Jackson.

Of most interest with respect to groundwater resource investigations is the extensive collection of groundwater elevation data. At 32 monitoring wells, groundwater elevation data have been collected since 1995. Each well is equipped with automatic data logging instrumentation which take hourly readings, then report a 24-hour average. A companion network of surface water flow measurement stations established in cooperation with the Teton County Natural Resources District provides correlations to evaluate surface-water and groundwater interactions. The current well network consists of 50 monitoring locations (see Figure 6).

Teton County (1999) provides a partial summary of the data collected to date, including 1997 graphical correlations with surface flows and 1995 - 1998 hydrographs for individual wells. A more comprehensive presentation and evaluation of these data is under development in the WSEO - Groundwater Division. Contacts for additional information on this on-going project are: Teton County - Don Barney (307-733-7190); Wyoming State Engineer’s Office - John Harju (307-777-7354).

Geologic Mapping

Although not specifically addressing groundwater resources in most cases, there has been extensive geologic mapping in the Snake/Salt River basin which provides a valuable tool to the evaluation of groundwater resources. Figure 3 presents a generalized, small-scale (1:500,000) overview. Many of the references cited above and listed in the bibliography contain more detailed local mapping. Those references in the bibliography known to include geologic maps are indicated. (This attribute has been included in the electronic version of the bibliography to allow sorting for publications including geologic maps.)

A very useful, although becoming seriously dated, resource for the identification of geologic mapping for a particular area is the map server maintained by the Wyoming Geographic Information Science Center (http://www.wygisc.uwyo.edu). This server is based on the 1985 - 1990 compilations of geologic mapping by the USGS, Geological Survey of Wyoming, and University of Wyoming Department of Geology (student theses and dissertations). (See bibliography entries under Greer.) One can enter the server with any location (point or polygon) and receive a listing of the geologic maps that cover that location.


References


14,675 acres “actually irrigated with groundwater in 1980"; “consumptive use of groundwater ... in 1980 is 5850 acre-feet”; “total groundwater withdrawal is an estimated 7800 acre-feet per year”; “about 75%” of that in Star Valley. (Ahern et al., 1981; p. 34-35).


2Town of Jackson, Teton Village, Teton Pines/Aspen/Wilson, Jackson Hole Golf and Tennis, Kelly, “Hog Island”, Hoback Junction, Alta, Rivermeadows, Indian Paintbrush.


3A monthly dataset of groundwater elevations (10/90 - 9/91) was developed for the west bank of the Snake River near Jackson by Nelson (1992). It shows the same general groundwater gradients and flow directions as the USGS study (Figure 4), with a seasonal fluctuation in groundwater elevations of 5 - 10 feet.


4500 gpdc * 4 people/home = 1.3 gpm


5For example, assuming 1,000 feet of saturated material beneath all portions of the basin where basement rocks are not exposed at the surface (i.e. leaving out the core of the Tetons, for example) and an average porosity of 10% indicates the presence of 175 million acre-ft of groundwater.


Bibliography

This section provides citations to the literature referenced above and additional sources of information relevant to the groundwater resources of the Snake/Salt River basin compiled from previous studies. The electronic version of this bibliography (“bibliography”) is provided in spreadsheet form to facilitate searching and sorting by various fields, e.g. date, map scale, etc.

Abegglen D.E., Wallace A.T., Williams R.E.; 1970; Effect of Drain Wells on Groundwater Quality of the Snake River Plain; Idaho Bureau of Mines and Geology, Pamphlet No. 148; Boise, ID.; 51p.

Ahern J.J., Collentine M., Cooke S.; 1981; Occurrence and Characteristics of Groundwater in the Green River Basin and Overthrust Belt, Wyoming; University of Wyoming Water Resources Research Institute, Environmental Protection Agency, Volume V-A; Laramie, WY; 123p.

Albee H.F.; 1973; Observation Peak Quadrangle, Teton and Lincoln Counties; U.S. Geological Survey Map GQ-1081; Scale: 1:24,000.

Albee H.F., Cullins H.L.; 1965; Preliminary Geologic Map of the Poker Peak and Palisades Reservoir (Alpine) Quadrangles, Bonneville County, Idaho, and Lincoln County, Wyoming (Superseded by U.S.G.S. Map GQ-1259, 1975); U.S. Geological Survey Open File 65-2; Scale: 1:24,000.

Albee H.F.; 1968; Munger Mountain Quadrangle, Teton and Lincoln Counties; U.S. Geological Survey Map GQ-705; Scale: 1:24,000.

Albee H.F.; 1972; Preliminary Geologic Map of Observation Peak Quadrangle, Teton and Lincoln Counties, Wyoming (Superseded by U.S.G.S. Map GQ-1081, 1973); U.S. Geological Survey Open File 72-1; Scale: 1:24,000.

Albee H.F., Cullins H.L.; 1975; Alpine Quadrangle, Bonneville County, Idaho, and Lincoln County, Wyoming; U.S. Geological Survey Map GQ-1259; Scale: 1:24,000.

Armstrong F.C., Cressman E.R.; 1963; The Bannock Thrust Zone Southeastern Idaho; U.S. Geological Survey Professional Paper 374-J; 22p.

Armstrong F.C., Oriel S.S.; 1965; Tectonic Development of the Idaho-Wyoming Thrust Belt; American Association of Petroleum Geologists Bulletin, Vol. 49.

AVI Professional Corporation; October 1991; Squaw Creek Water Supply Project, Level I Study.

Behrendt J.C., Tibbetts B.L., Bonini W.E., Lavin P.M; 1968; A Geophysical Study in Grand Teton National Park and Vicinity, Teton County, Wyoming, with Sections on Stratigraphy and Structure, by J.D. Love, and Precambrian Rocks, by J.C. Reed, Jr.; U.S. Geological Survey Professional Paper 516-E; 23p.

Benson, A.L.; 1966; Devonian Stratigraphy of Western Wyoming and Adjacent Areas; American Association of Petroleum Geologists, Vol. 50, No. 12.

Blanchard M.R.; 1990; Discrimination Between Flow-Through and Pulse-Through Components of an Alpine Carbonate Aquifer, Salt River Range, Wyoming; University of Wyoming, Thesis; Laramie, Wyoming; 77p.

Boyd T.L.; March 2002; Western States Geothermal Databases CD; Oregon Institute of Technology, Geo-Heat Center; GHC Bulletin, March 2002.

Bradley C.C.; 1956; The Pre-Cambrian Complex of Grand Teton National Park, Wyoming; Wyoming Geological Association Guidebook; Eleventh Annual Field Conference in Jackson Hole; p. 34-42.

Bragdon F.F.; 1965; Geology of the Fish Spring Creek and Adjacent Area, Lincoln and Sublette Counties, Wyoming; University of Wyoming, Thesis; Map included; Scale: 1:20,436.

Breckenridge R.M., Hinckley B.S.; March 1978; Thermal Springs of Wyoming; The Geological Survey of Wyoming, Bulletin 60; 104p.

BRS, Inc.; November 1999; Afton Water Supply Project - Level II, Executive Summary.

BRS, Inc.; November 1999; Afton Water Supply Project - Level II, Final Report.

Bureau of Reclamation; 1979; Salmon Falls Division Groundwater Investigations and Aspects of Pumping from the Snake Plain Aquifer–Draft; Bureau of Reclamation; Denver, CO.; 83p.

Bureau of Reclamation; nd; Salmon Falls Division Definite Plan Report; Bureau of Reclamation; Denver, CO.

Bureau of Reclamation, Army Corps of Engineers; 1961; Upper Snake River Basin, Wyoming-Idaho-Utah-Nevada-Oregon–Final Report; Bureau of Reclamation, Region 1. Denver, CO.

Bureau of Reclamation; 1951; Farm Development and Groundwater Supply - 1950 Season - North Side Pumping Division, Minidoka Project; Bureau of Reclamation; Denver, CO.

Bureau of Reclamation, U.S. Geological Survey; 1961; Upper Snake River Basin, Wyoming-Idaho-Utah-Nevada-Oregon - Volume III - Part 2 - Coordination and Reports of Cooperating Agencies; Bureau of Reclamation; Denver, CO.

Case J.C.; 1991; Earthquakes and Active Faults in Wyoming; Geological Survey of Wyoming, Laramie, Wyoming; 58p.

Case J.C., Larsen L.L., Boyd C.S., Cannia J.C.; 1995; Earthquake Epicenters and Suspected Active Faults with Surficial Expression in Wyoming; Geological Survey of Wyoming, Laramie, Wyoming, Map; Scale: 1:1,000,000.

Christiansen R.L., Blank H.R. Jr., Love J.D., Reed J.C. Jr.; 1978; Geologic Map of the Grassy Lake Reservoir Quadrangle, Yellowstone National Park and Vicinity, Wyoming; U.S. Geological Survey Geologic Quadrangle Map GQ-1459; Scale: 1:62,500.

Clark G.M.; 1994; Assessment of Selected Constituents in Surface Water of the Upper Snake River Basin, Idaho and Western Wyoming, Water Years 1975-89; U.S. Geological Survey Water-Resources Investigations Report 93-4229; 49p.

Clark G.M., Maret T.R., Rupert M.G., Maupin M.A., Low W.H., Ott D.S.; 1998; Water Quality in the Upper Snake River Basin, Idaho and Wyoming, 1992-95; U.S. Geological Survey Circular 1160; Reston, VA.; 35p.

Corsi E.W.; 1990; The Hills of Home; Afton, Wyoming; Afton Thrifty Print; 361p.

Cox E.R.; 1977; Preliminary Study of Subsurface Wastewater Movement in and near Grand Teton National Park, Wyoming, Through October 1976; U.S. Geological Survey, Water Resources Division, Open-File Report No. 77-25; Cheyenne, WY.; 35p.

Cox E.R.; 1976; Water Resources of Northwestern Wyoming; U.S. Geological Survey Atlas HA-558; Scale: 1:253,440.

Cox E.R.; 1974; Water Resources of Grand Teton National Park, Wyoming; U.S. Geological Survey Open-File Report; Cheyenne, WY.; 114p.

Cox E.R.; 1973; Water Resources of Yellowstone National Park, Wyoming, Montana, and Idaho; U.S. Geological Survey Open File Report; 161p.

Craig G.S. Jr., Ringen B.H., Cox E.R.; nd; Hydrologic Data for the Cache Creek-Bear Thrust Environmental Impact Statement near Jackson, Wyoming; U.S. Geological Survey, Water Resources Division, Open-File Report No. 81-410; Cheyenne, WY.

Crandall D.L.; 1962; Upper Snake River Basin, Idaho, Wyoming, Surface and Underground Water -- When Combined, A New Water Supply for the Future; Colorado School of Mines Quarterly, 57(4):113-130.

Crosthwaite E.G.; 1979; Chemical Analysis of Groundwater Related to Geothermal Investigations in the Teton River Area, Eastern Idaho; U.S. Geological Survey Open-File Report No. 79-687; Boise, ID.; 14p. Department of Agriculture, Forest Service; 1974; Spread Creek-North Gros Ventre Planning Unit, Bridger-Teton National Forest, Wyoming - Final Environmental Impact Statement; Department of Agriculture, Forest Service; Cheyenne, WY.; 236p.

Eardley A.J., Horberg, Leland, Nelson, V.E. and Church, Victor; 1944; Hoback-Gros Ventre-Teton Field Conference; University of Michigan Field Conference; Geologic Map; Privately Printed.

Eddy-Miller C.A., Norris J.R.; 2000; Pesticides in Ground Water; Lincoln County, Wyoming, 1998-99; U.S. Geological Survey Fact Sheet 0033-00; Reston, VA.; 4p.

Eddy-Miller C.A., Plafcan M., Clark M.L.; 1996; Water Resources of Lincoln County, Wyoming; U.S. Geological Survey Water Resources Investigation Report 96-4246; Reston, VA.; 131p.; 3 sheets.

Forsgren Associates; November 1997; Strawberry Canal Rehabilitation Project, Level II, Feasibility Study, Executive Summary.

Forsgren Associates; November 1997; Strawberry Canal Rehabilitation Project, Level II, Feasibility Study.

Forsgren Associates; November 1997; Thayne Water Supply, Executive Summary.

Forsgren Associates; November 1997; Thayne Water Supply.

Forsgren Associates; November 1995; Thayne Area Water Supply, Executive Summary.

Forsgren Associates; November 1995; Thayne Area Water Supply, Level I Study.

Forsgren Associates; December 1993; Stewart Creek Irrigation Pipeline Level II Study, Final Report.

Forsgren Associates; November 1993; Star Valley Level II Study, Etna Water and Sewer District Water Supply System, Executive Summary.

Forsgren Associates; November 1993; Star Valley Level II Study, Etna Water and Sewer District Water Supply System.

Forsgren Associates; December 1992; Star Valley Level II Study, Freedom Water and Sewer District Water Supply System, Executive Summary.

Forsgren Associates; December 1992; Star Valley Level II Study, Freedom Water and Sewer District Water Supply System, Final Report.

Forsgren Associates; November 1991; Star Valley Municipal Water Supply Level II Study, Executive Summary.

Forsgren Associates; November 1991; Star Valley Municipal Water Supply Level II Study, Report of the Smoot Water Supply System, Final Report.

Forsgren Associates; November 1991; Star Valley Municipal Water Supply Level II Study, Report of the Osmond Water Supply System, Final Report.

Forsgren Associates; November 1991; Star Valley Municipal Water Supply Level II Study, Report of the Grover Water Supply System, Final Report.

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APPENDIX A

Figures


APPENDIX B

Lithologic and Water-Bearing Characteristics
of Geologic Units in the Snake/Salt River Basin


Appendix B - Lithologic and water-bearing characteristics of geologic units in the Snake/Salt River Basin
ErathemSystemSeriesGeologic
Unit
Approx-
imate
thickness (ft)
LithologyWater-bearing characteristics1Reported1, estimated,
measured, or
range of most
common water
yields (gpm)
CenozoicQuaternary2Alluvium and colluviumup to 4103
0 - >4004
“Unconsolidated sand and gravel interbedded with silt and clay. The maximum thickness of the alluvium in the Bear (and) Salt... River valleys is unknown; however, wells that are 200 ft deep have not penetrated the full thickness in these areas.”6

TDEM geophysical exploration indicates thicknesses up to 2,400 ft in the Snake River aquifer.7

Ground-water possibilities good in coarser deposits, but poor where silt and clay predominate. Clean sand and gravel near perennial streams would probably have yields of approximately 500 gpm.5

“Sand and gravel in alluvium is the most and municipal wells in the Bear (and) utilized aquifer in the thrust belt. Irrigation Salt... River valleys yield 1,000 to 2,000 gpm. Yields of wells that tap alluvium are dependent on the thickness, the sorting of the saturated sand and gravel, and the well construction.“6

50-5003

Reported yields ranged from a few to 3,000 gal/min per well.

CenozoicQuaternary2Gravel,pediment,and fan deposits15-305“Gravel, pebble to boulder size, sand, and silt. Located at several terrace levels above the streams and in scattered patches along highlands; includes some glacial outwashmaterial.”5“Known well yields are less than 20 gpm.”5<20 5

Reported yields ranged from a few to 1,650 gal/min per well.

CenozoicQuaternary2Glacial
deposits
0- >2008“Till and outwash of sand, gravel, and boulders.”9

“Poorly sorted silt, sand, gravel, and boulders as much as 40 feet in diameter.”6

Glacial deposits may yield small quantities of water to wells. Water yield is limited due to poorly sorted material and smallsaturated thickness.6<205
CenozoicQuaternary2Landslide
deposits
0-10010“Locally includes intermixed landslide and glacial deposits, talus, and rock-glacierdeposits.”9

Probably would not yield more than a few gal/min per well. Yields water to numerous springs.10

“Rock debris is not a potential source of water because of its poorly sorted material and small saturated thickness.”6--
CenozoicQuaternary2Dune sand
and loess
<105Unconsolidated sand and silt.5

“Includes active and dormant dunes.”9

“Generally too thin to hold much water, but aids recharge to underlying formations.”5--
CenozoicQuaternaryPleistocene11 Rhyolite & basalt flows, tuff, and intrusive igneous rocksat least 70011Lava Creek Tuff of the Yellowstone Group is gray to brown, welded rhyolite ash-flow. Lewis Canyon Rhyolite is devitrified flow containing phenocrysts of quartz, plagioclase, sanidine, and clinopyroxene.11May yield a few tens of gpm per well from porous and fractured zones.10--
CenozoicQuaternary
and/or Tertiary
Pleistocene and/or PlioceneConglomerateas much as 40011 Paleozoic clasts in a lithified carbonate matrix.May yield a few tens of gpm per well.--
CenozoicTertiaryPlioceneHuckleberry Ridge Tuff of Yellowstone Group0-1,50011Lavender to grayish-brown, welded and devitrified rhyolitic ash-flow tuff containing abundant phenocrysts of quartz, sanidine, and sodic plagioclase, sparse opaque oxides, clinopyroxene, and fayalitic olivine.11May yield a few tens of gpm per well from porous and fractured zones. Estimated yield ranged from 3 to 5 gpm for 2 springs.
CenozoicTertiaryPliocene and MioceneIntrusive and extrusive igneous rocks0-80011Includes gray, porphyritic andesite flows; light-gray to tan, fine-grained rhyolite intrusions; and medium-to dark-gray fine-grained dacite flows.11Probably would not yield more than a few gpm per well.Measued well yield was 50 gpm.
CenozoicTertiaryPlioceneHeart Lake Conglomerate--Abundant gray limestone and dolomite clasts and sparse rhyolite and quartzite clasts in a talc and clay matrix.----
CenozoicTertiaryPlioceneShooting Iron Formation>10011Greenish-gray to pink, tuffaceous, lacustrine and fluviatile claystone and siltstone, fine-grained sandstone, and conglomerate.----
CenozoicTertiaryLower Pliocene11 and MioceneConant Creek Tuff0-30011Gray to buff and pale-lavender, phenocryst-poor, welded rhyolite tuff.11----
CenozoicTertiaryPliocene and MioceneSalt Lake Formation<10006“White, gray, and green limy tuff, siltstone, sandstone, and conglomerate.”9

“Pale-reddish gray conglomerate, grit, sandstone, siltstone, clay, and white volcanic ash. The formation is most extensive in theStar Valley, where it has a maximum thickness of about 1,000 ft.”6

The availability of water from this type of aquifer is limited because the conglomerates are usually well indurated,poorly sorted, and have little primary permeability. Springs issue from the conglomerates on side hills, but their flows rarely exceed 20 gpm.6

Nonetheless, this formation is the source of 2,000+ gpm springs near Thayne and of several 500 - 1000 gpm municipal supply wells in Star Valley.

generally <206, but up to 2,000 under locally favorable conditions
CenozoicTertiaryMioceneTeewinot Formation>6,00011White to light-gray, porous limestone, claystone, and pumicite. Upper part is thin-bedded claystone, marlstone, and tuff; middle part is conglomerate of limestone, quartzite, and obsidian clasts as much as 110 ft thick; lower two-thirds is nodular porous limestone in beds 100-200 ft thick interbedded with pumicite beds 20-75 ft thick.11--Yields as much as 120 gpm per well from fractures and solution channels in limestone.10 Estimated spring yield was 5 gpm and measured well yield was 17.4 gpm.
CenozoicTertiaryMioceneCamp Davis Formationabout 5,20012Upper part is red, well-consolidated, calcareous conglomerate; middle part is poorly consolidated, calcareous conglomerate interbedded with silty and sandy mudstone; lower part is brownish-gray, well-cemented, calcareous, sandy conglomerate.12May yield a few tens of gpm per well from conglomerate.10--
CenozoicTertiaryMioceneColter Formation<7,00010Upper part is light-gray, green, and brown tuff, sandstone, claystone, and mafic volcanic conglomerate; lower part is light-gray tuffaceous, massive to irregularly bedded, poorly cemented sandstone.11May yield a few gpm per well from conglomerate, sandstone, and fractures in basalt and andesite.10Estimated yield of spring was 1 gpm.
CenozoicTertiaryEoceneIntrusive igneous rocks--Felsic and mafic igneous bodies.----
CenozoicTertiaryEoceneWiggins Formation (Thorofare Creek Group, Absaroka Volcanics Supergroup)0-7011 Light-gray, volcanic conglomerate, white tuff, and yellow, white, red, green, and pink bentonitic claystone.11Probably would not yield more than a few gpm per well.
CenozoicTertiaryEoceneTepee Trail Formation13 (Thorofare Creek Group, Absaroka Volcanics Supergroup)--Green and olive-drab, hard andesitic conglomerate, sandstone, and claystone.Probably would not yield more than a few gpm per well.Estimated yield of spring was 50 gpm.
CenozoicTertiaryEocene and PaleoceneWasatch Formation La Barge and Chappo Members14<1,7005 La Barge Member consists of red and brown mudstone and conglomerate, yellow sandstone and pisolitic limestone.5

Chappo Member consists of red to gray conglomerate and sandstone.5

Unknown--
CenozoicTertiaryPaleoceneHoback Formation<15,00010Interbedded gray sandstone and claystone containing thick red and gray conglomerate.May yield a few tens of gpm per well from sandstone.10--
CenozoicTertiaryPaleoceneDevils Basin Formation--Light-gray sandstone interbedded with green and gray claystone, sparse coal, and carbonaceous shale.----
Cenozoic and MesozoicTertiary and CretaceousPaleocene and Upper CretaceousPinyon Conglomerate0-3,80011 Rusty-brown conglomerate composed of quartzite roundstones in matrix of rusty coarse-grained sandstone containing gold flakes. Sporadic boulders of older conglomerate and quartzite are 5-8 ft in diameter.11May yield a few tens of gpm per well.10--
CenozoicCretaceousUpper CretaceousHarebell Formationas much as 10,00011Conglomerate consisting of quartzite roundstones in matrix of brown gold-bearing sandstone; brown, gray, and dull green, silty, hard, tuffaceous sandstone, rich in magnetite; gray, dark green, black and mustard yellow, silty, tuffaceous claystone; and marine or brackish-water fossils in some horizons.11May yield a few tens of gpm per well from conglomerate and sandstone.10Measured discharge of well was 12 gpm
MesozoicCretaceousUpper CretaceousAdavilleFormation151,400-
5,0003
<2,1005
“Brown and buff fine- to medium-grained calcareous sandstone, gray carbonaceousmudstone, and numerous coal beds. The proportions of sandstone to mudstone areabout equal. Thickness varies because of the irregularity of the unconformity that separates the Adaville and overlying Cretaceous rocks.“6“Generally considered a minor aquifer of the Overthrust Belt area...”3

“Small quantities of water are available from sandstone in the base of the Adaville Formation.”6

--
MesozoicCretaceousUpper CretaceousSohare Formation15as much as 2,40011Gray and brown, lenticular, fine-grained sandstone interbedded with light- and dark-gray shale and siltstone and containing thin coal beds. Largely nonmarine.11May yield a few tens of gpm per well from sandstone.10--
MesozoicCretaceousUpper CretaceousBacon Ridge Formation151,000-
1,50011
Tan to gray, thick-bedded, fine-grained sandstone containing abundant marine fossils. Interbedded with gray, marine and brackish-water shale and siltstone and thick coal beds. Contains thin bentonite beds in upper and lower parts. Quartzite boulder conglomerate in lower part intertongues with marine strata.11May yield a few tens of gpm per well from sandstone.10Estimated spring discharge was 800 gpm.
MesozoicCretaceousUpper CretaceousCody Shale151,400-
2,20011
Dull-gray marine shale interbedded with lesser amounts of gray siltstone and gray, fine-grained, glauconitic sandstone and bentonite.11Probably would not yield more than a few gpm per well.10--
MesozoicCretaceousUpper CretaceousSteele Shale15--Gray marine shale containing numerous bentonite beds and thin lenticular sandstone.----
MesozoicCretaceousUpper CretaceousBlind Bull
Formation15
<9,2005“Fine-grained to conglomeratic sandstone,siltstone, and shale with some beds of bentonite and coal.”6Small quantities of water are available from sandstone layers in the Blind Bull Formation.6--
MesozoicCretaceousUpper CretaceousHilliard Shale153,000-
6,800?3
“Dark-gray to tan claystone, siltstone, and sandy shale.”9“Major regional confining unit of Green River Basin and Overthrust Belt. Locallyyields small quantities to wells from sand lenses.”3--
MesozoicCretaceousUpper CretaceousFrontier
Formation
l,l00-
3,000?3
“Gray, fine- to medium-grained sandstone, andgray mudstone, claystone, and siltstone with some beds of coal. The Oyster Ridge Sandstone Member is near the top of the formation and it contains numerous oyster shells.”6“Sandstone aquifers in the Frontier Formation are capable of yielding moderate quantities of water....”65-503
MesozoicCretaceousLower
Cretaceous
Aspen Shale400-
2,2003
1,100-
2,0005
“Light- to dark-gray siliceous tuffaceous shale and siltstone, thin bentonite beds, andquartzitic sandstone.”9

“Light gray to black shale, gray fine-grained sandstone, and white to gray porcelanite.”6

Locally utilized aquifer, maximum spring and well yields 25 to 30 gpm. Water yields are mainly from stray sands andfracture zones.”325-303
MesozoicCretaceousLower CretaceousBear River
Formation
800-
1,5003,6
“Black shale, fine-grained brown sandstone, thin limestone, and bentonite beds.”9

“Mainly gray to black fissile shale with interbeds of gray sandstone. Thickness generally ranges from 800 to 1,500 ft.”6

“Minor aquifer with spring yields generally 4 to 15 gpm and similar well yields.”3

“Small quantities of water are available from sandstone in the Bear River Formation.”6

4-153
MesozoicCretaceousLower CretaceousGannett Group includes:
Smoot
Formation,
Draney
Limestone,
Bechler
Conglomerate,
Peterson
Limestone,
Ephraim
Conglomerate
800-
5,0003,6
Lithologies of the Gannett Group include: brick-red and maroon siltstone and clay-stone, red to brown calcareous to quartzitic sandstone, red to brown conglomerate, and gray to tan nodular limestone (Ephraim Conglomerate); finely crystalline limestone (Peterson Limestone); red sandstone and conglomerate, and purplish- to reddish-gray siltstone and mudstone with thin limestone interbeds (Bechler Conglomerate); gray finely crystalline limestone and gray calcareous siltstone (Draney Limestone); and red siltstone and mudstone (Smoot Formation).6“Water-bearing units restricted to sandstones and conglomerate in lower part.”3

Rocks in the Gannett Group are mostly impermeable and in most areas they are only capable of yielding small quantitiesof water. Where the conglomerates are fractured, moderate quantities areavailable.6

5-753
MesozoicJurassicUpper and Middle JurassicStump
Formation
90- 1206“Green to greenish-gray glauconitic sandstone, siltstone and limestone.”6The sandstone of the Stump Formation is relatively impermeable and in most areasis capable of yielding only small quantities of water.6 Unit is considered a poor aquifer.3
MesozoicJurassicUpper and Middle JurassicPreuss
Sandstone or
Preuss
Redbeds
360-
1,6005
Red, maroon, brown, and orange calcareous siltstone, mudstone, and sandstone, and some beds of rock salt in the Overthrust Belt.6The Preuss Sandstone or Preuss Redbeds is relatively impermeable and in most areas is capable of yielding only small quantities of water.6--
MesozoicJurassicMiddle JurassicTwin Creek
Limestone
800-
3,8003
980-
3,3005
“Light-gray to black limestone and shale in the upper part, and red, brown, and orange claystone and gray mainly brecciated but partly honeycombed limestone in the lower part... 3,800-ft thick in the southern part of Lincoln County.”6Upper part of the Twin Creek Limestone is relatively impermeable and in most areasis capable of yielding only small quantities of water.6

“Minor aquifer in Overthrust Belt.”3

20-3003
MesozoicJurassic(?)
Triassic(?)

Nugget Sandstone750-
1,3003,6
“Varicolored (generally pink to salmon) crossbedded fine- to medium-grained well-sorted quartzitic sandstone, and a few beds of maroon, red, and brown mudstone in the lower part. About 1,300 ft thick in southern part of Lincoln County.”6 The Nugget Sandstone is capable of yielding moderate to large quantities of water where outcrop or recharge areas arelarge; bedding is continuous and not offset by faults, and in topographic lows where large thicknesses occur. Many springsissue from the Nugget and flows greater than 1,000 gpm are common.63-3003
MesozoicTriassicUpper and Lower TriassicAnkareh
Formation
200-8003
200-6006
“Red to brown shale, siltstone, and fine-grainedsandstone, and, locally, greenish-gray limestone in about the middle part. About 200 ft thick in the northern part of Lincoln Countyand about 600 ft thick in the southern part.”6Rocks in the Ankareh Formation are relatively impermeable and in most areas are probably capable of only yielding small quantities of water.6

“Minor regional aquifer, locally confining.”3

--
MesozoicTriassicLower
Triassic
Thaynes
Limestone
1,100-
2,6003,6
700-
1 3005
980-
1,6005
“Mainly buff to dark-gray silty limestone, and red to tan siltstone and shale predominately in the upper part. About 1,100 ft thick in the northern part of Lincoln County and 2,400 to 2,600 ft thick in the southern part.”6 “Where the Thaynes has secondary permeability in the form of fractures and (or) solution openings, the limestone will yield moderate quantities of water to wells.”6

“Generally considered a regional aquifer with spring flows of 5 to 1,800 gpm...”3

5-1,800 3
MesozoicTriassicLower
Triassic
Woodside
Shale
350-6003
350-5006
“Mainly red and orange partly anhydritic siltstone and mudstone, and some orange fine-grained sandstone.”6Rocks in the Woodside Shale are mostly impermeable and in most areas they are probably capable of only yielding small quantities of water.6--
MesozoicTriassicLower
Triassic
Dinwoody
Formation
250-7003“Gray to olive-drab dolomitic siltstone.”9Rocks in the Dinwoody Formation are mostly impermeable and in most areas are probably capable of only yielding small quantities of water.6--
MesozoicTriassicUpper and Lower TriassicChugwater
Formation
--“Chugwater-red siltstone and shale.”9Unknown--
PaleozoicPermian
Phosphoria
Formation16
and related
rocks
200-4003
230-3605
“Upper part is dark- to light-gray chert and shale with black shale and phosphorite at top; lower part is black shale, phosphorite, and cherty dolomite.”9

“Mainly phosphatic, carbonaceous, and cherty shale and sandstone.”6

Rocks in the Phosphoria Formation are mostly impermeable and in most areas are probably capable of only yielding small quantities of water. Where extensively fractured, the Phosphoria is capable of yielding moderate quantities of water.6

“Unit is minor aquifer, locally confining.”3

--
PaleozoicPermian and PennsylvanianPermian, Upper and Middle PennsylvanianTensleep
Sandstone
450-
1,0003
White, gray, and pink well-sorted fine-grained sandstone and quartzite, and thin layers of white siliceous, dolomitic limestone.6 “Sandstone aquifer in the Wells Formation and Tensleep Sandstone are capable ofyielding moderate to large quantities of water. Availability is dependent upon local conditions of recharge, continuity of beds and development of permeability. These sandstones on topographic highs may be drained, especially if underlying limestones have extensive solution development.”6

“Major aquifer of Paleozoic System.”3

210-7003
PaleozoicPermian and Pennsylvanian Permian, Upper and Middle PennsylvanianWells
Formation
450-
1,0006
“Gray thick-bedded quartzite, calcareous sandstone, and limestone mainly in the upper part.”6“Sandstone aquifer in the Wells Formation and Tensleep Sandstone are capable of yielding moderate to large quantities of water. Availability is dependent upon local conditions of recharge, continuity of beds and development of permeability. These sandstones on topographic highs may bedrained, especially if underlying limestones have extensive solution development.”6--
PaleozoicPennsylvanian/ MississippianMiddle and Lower Pennsylvanian and Upper MississippianAmsden
Formation
400-7003
150-3905
“Varicolored mudstone, siltstone, and sandstone, and gray cherty limestone.”6Few hydrogeologic data are available for the Amsden Formation. Small quantities of water may be available from the cherty limestone in the Amsden Formation, but, on topographic highs, the Amsden is probably well drained, especially if underlying limestones have extensive solution development.6

“Minor aquifer in Green River Basin, but locally confining in Overthrust Belt...”3

--
PaleozoicMississippianUpper and Lower MississippianMadison
Limestone
800-
2,0003
“Gray, tan, and brown thin-bedded to partly massive cherty and brecciated limestone and gray to tan thick-bedded massive dolomite.”6“Major regional aquifer... Excellent solution and fracture permeability... This permeability is produced by solution zones along bedding plane partings and joints.”3<1003
PaleozoicDevonianLower Mississippian and Upper DevonianDarby
Formation
400-
1,0003,6 <8905
“Gray to brown thin-bedded massive dolomite and limestone, and black, red, and yellow siltstone... About 1,000 ft thick along the Wyoming-Utah border southwest of Sage.”6Availability of water from limestone and dolomite aquifers is largely dependent on the secondary permeability in the form of solution openings and fractures.6--
PaleozoicSilurianUpper and Middle SilurianLaketown
Dolomite
980-
1,3005
“Light-gray thick-bedded finely crystalline dolomite.”9Not much is known about this aquifer. Water availability is probably dependent upon secondary permeability.--
PaleozoicOrdovicianUpper
Ordovician
Bighorn
Dolomite
400-
1,0003
“Gray fine- to medium-grained massive dolomite and dolomitic limestone that has rough pitted surfaces upon weathering.”6 Highly productive aquifer where fracture, secondary solution and bedding plane permeability are well developed.”6--
PaleozoicCambrianUpper
Cambrian
Gallatin
Limestone
125-
1,0003
“Dark-gray brown-mottled thin-bedded limestone and gray partly dolomitic limestone with some beds of conglomerate.”6“Well and spring data are not available; however, lithology as well as fracture and secondary solution permeability develop-ment are indicative of a potentially productive aquifer.”3--
PaleozoicCambrianUpper and
Middle
Cambrian
Gros Ventre
Formation
500-
2,5003
“Gray and green shale with some conglomerate in the upper part, blue to gray rustymottled limestone in the middle part, and green and red hematitic shale in the lower part.”6Few hydrologic data are available. The Gros Ventre Formation consists predominately of poorly permeable rock and is probably not an important aquifer.6

“Unit is generally considered a regional aquitard with low vertical permeability due to upper and lower shales.”3

--
PaleozoicCambrianMiddle
Cambrian
Flathead
Sandstone
175-2003,6“White to pink fine-grained quartzite and some lenses of coarse-grained sandstone. The upper part contains some green silty shale interbeds,and the basal part is conglomeratic.”6Few hydrologic data are available. Based on lithology, the Flathead is probably a potential source of water.6--
Middle and Early ProterozoicPrecambrian
Mafic intrusive
rocks
----May yield a few tens of gpm per well from fractures or from weathered zone at top of unit.Estimated spring discharges were 5-12 gpm.
Late ArcheanPrecambrian
Granite
gneiss-
--Webb Canyon Gneiss is medium- to coarse-grained biotite- and hornblende-bearing quartz monzonite gneiss. Contains allanite.11May yield a few tens of gpm per well from fractures or from weathered zone at top of unit.--
Late and Middle ArcheanPrecambrian
Metasedimentary
and
metavolcanic
rocks.
--Amphibolite, hornblende gneiss, biotite gneiss, quartzite, iron-formation, metaconglomerate, marble, and pelitic schist.9May yield a few tens of gpm per well from fractures.
Late and Middle ArcheanPrecambrian
Metamorphosed
mafic and
ultramafic rocks
--Teton Range contains gray to dark-green, coarse-grained Rendezvous Metagabbro with clots of green hornblende in matrix of light-gray plagioclase.11 Gros Ventre Range contains hornblende, gneiss, and serpentinite.May yield a few tens of gpm per well from fractures or from weathered zone at top of unit.Yields as much as 200 gpm to individual springs in the Teton Range.10 Estimated spring discharges were 5-12 gpm.
Late ArcheanPrecambrian
Granite rocks of
2,600-Ma age group
--Teton Range contains light colored, medium- to fine-grained Mount Owen Quartz Monzonite with muscovite- and biotite-bearing pegmatite.11 Gros Ventre and Washakie Ranges contain granite rocks.May yield a few tens of gpm per well from fractures or weathered zone at top of unit.--
1Reported and typical well yields do not necessarily reflect maximum potential aquifer yields.
2Sequence in table does not indicate age relative to other Quaternary entries.
3Ahern, Collentine, and Cooke, 1981.
4Behrendt and others, 1968.
5Eddy-Miller et al., 1996.
6Lines and Glass, 1975.
7Nolan and Miller, 1995.
8Outwash at south end of Jackson Lake (Pierce and Good, 1992).
9Love and Christiansen, 1985.
10Cox, 1976.
11Love and others, 1992.
12Schroeder, 1974.
13Sediments not extensive enough to be shown on plate 1, but have been verified.
14Only present in upper Hoback River basin.
15Sequence in table does not indicate age relative to other Upper Cretaceous entries.
16In Wyoming, the Phosphoria Formation is synonymous with the Park City Formation (Lane, 1973, p. 4).


APPENDIX C

WSEO Snake/Salt River Basin Permits


APPENDIX D

USGS Snake/Salt River Basin Wells