Home Page     News & Information     River Basin Plans     Basin Advisory Groups     Planning Products    


The Colorado River is the primary source of domestic water supply for nearly 23 million people in seven southwestern states. It also provides irrigation water used on over 3.5 million acres of farmland within the basin and hundreds of thousands more outside the Basin to produce among other crops much of the high-value winter fruit and vegetable crop in the United States. In addition, Mexico is guaranteed by treaty a certain amount of water from the Colorado River. Due to the limited water supply and the long-recognized value of the water supplies needed to maintain the economy of this region and to permit it to grow, the use of Colorado River water has been regulated for 75 years. The collection of legal documents that accomplishes this is known as the "Law of the River," and consists of an international treaty, interstate compacts, numerous federal statute and regulations, and a U.S. Supreme Court decree.

Also of significance are the federal statutes and regulations which govern the water quality of the Colorado River. All states regulate water quality constituents related to health concerns. In some states, other substances are also regulated for economic and aesthetic purposes. Among these latter constituents is total dissolved solids (TDS) concentration or salinity, which is typically measured in Milligrams per liter (mg/l). (For all practical purposes, the terms "total dissolved solids" and "salinity" concentration are synonymous and can be used interchangeably.) The primary reason for the regulation of total dissolved solids is the economic impacts high salinity can have on those using such supplies. Water containing high salinity will more quickly corrode plumbing and water-using appliances and industrial equipment, and will have limited uses for irrigation of agricultural crops and landscaping egetation.

Its Nature

The TDS in the waters of the Colorado River is composed of a number of chemical substances which reach the river from several different sources. It is estimated that approximately one-half of the salinity comes from natural sources, and the other half from man's uses of the water and his activities near the river. Millions of years ago, much of the land which lies within the Colorado River Basin (see Figure 1) was once the bottom of a large inland sea. The sea evaporated leaving all of the solids that were dissolved in its waters as deposits of salts. The resulting rocks that were formed from the deposits contain these salts. Soils formed from the weathered rocks are also high in the deposited salts. As the soil erodes naturally, or is disturbed by man's activities, runoff from precipitation and irrigation carries redissolved salts soils into the river. In addition, numerous saline springs, transporting very high levels of d salts picked up by deep groundwater as it moves toward the surface, contribute measurably to the salt loading of the Colorado River.

Within the realm of man-caused contributions to Colorado River salinity, the primary source is irrigation return flows, which contain fertilizers and chemical residuals in addition to redissolved salts from the soil. Some salts are also added due to use of detergents and, the addition of waste matter to the water. Vast areas of the region are owned by the federal government, and are used for purposes such as logging, grazing, or recreation. Natural erosion and man-induced erosion associated with such activities brings additional dissolved salts to the river. In addition, evaporation from the surfaces of the large federally constructed reservoirs such as Lake Mead and Lake Powell is a factor. Reservoir evaporation removes water from the system, concentrating the salts in a reduced amount of water.

Figure 1

At its source high in the Rocky Mountains, the TDS concentration of the Colorado River is typically 50 mg/l or less. As the river flows downstream large amounts of salts are picked up, and at Hoover Dam the river delivers about 9 million tons of dissolved salts annually. Upon reaching the last diversion point in the United States at Imperial Dam, concentration frequently exceeds 800 mg/l.

Its Impacts

As development in the basin states continues, the level of salinity concentration in the Colorado River, if unchecked, would continue to increase. The use of the river's water for certain purposes would become limited for economic or aesthetic reasons. The impacts of increased salinity would affect practically all present uses of the river in the United States and Mexico.

For Municipal and Industrial (M&I) uses, there would be increased water treatment costs, accelerated pipe deterioration and appliance wear, limited use for landscape irrigation, increased use of soap and detergents, and decreased water palatability.

Within Agricultural uses, there would be lower crop yield, altered crop patterns, higher soil leaching and drainage requirements, and higher management costs.

Generally for M&I uses, if a water supply has a salinity concentration of less than 500 mg/l it is presumed to have little or no negative economic or aesthetic impacts. Once this level reaches 1,000 mg/l, negative impacts on M&I uses become significant; at 1,500 mg/l, use for many M&I purposes becomes restricted without additional treatment prior to use. For irrigation purposes (both for commercial agricultural applications and landscaping), use starts to become limited once the TDS concentration reaches 700 to 850 mg/l, depending upon soil conditions and the type of vegetation being irrigated.

A February 1988 report, "Estimating Economic Impacts of Salinity of the Colorado River", provided some estimates of damages resulting from the high salinity in the river. Using 1986 dollars and the salinity concentration in that same year, annual damages were estimated at $310 million. Taking into account ten years of inflation, as well as the fact that Colorado River salinity concentrations in 1986 (see Figure 2) were near their lowest level at Parker Dam in decades (535 mg/l vs. 661 mg/l in 1995), this damage amount would be considerably higher today. Using the methodology of the 1988 study, it is estimated that damages in 1996 were about $750 million. Figure 3 illustrates further how these economic impacts are distributed among the various users of Colorado River water.

Figure 2

Another factor to consider, which has major economic impacts is the effects of high-salinity water on water reclamation and groundwater replenishment activities. The Southern California region has made a significant commitment to include both of these activities to make more efficient use of its local and imported water resources. Major investments have been made in facilities to reclaim and recycle water for irrigation, industrial, and other purposes. Since these processes do not normally reduce TDS in a cost-effective manner, the economic attractiveness of such projects quickly deteriorates as salinity in source water supplies rise. Similarly, water quality regulations intended to preserve groundwater basin integrity, when applied to replenishment water supplies, often limit the use of water more saline than the receiving groundwater basin. As key elements in Southern California's overall water management strategy. The Colorado River provides a large proportion of the supply (about 30%). Its salinity is key to the success of many such resource management projects.

Figure 3


There are a number of parties that can be considered stakeholders when it comes to the issue of Colorado River salinity. In general terms, they can be regarded as falling into two categories: water users and resource managers.

Water Users

This includes all parties that derive direct economic benefits through the availability and use of Colorado River water. Entities such as The Metropolitan Water District of Southern California (on behalf of the Los Angeles and San Diego urban areas) and the rapidly growing Las Vegas, Phoenix, and Tucson areas are reliant on the continued availability of high-quality water from the Colorado River. In addition, the enormously productive California agricultural areas of Palo Verde and the Coachella and Imperial valleys, as well as those in Arizona require suitable quality water. Users in the Upper Colorado River Basin states of Colorado, New Mexico, Utah, and Wyoming are also stakeholders as they implement salinity management efforts. Within the Colorado River Basin, Native American tribes are significant users of the river, and benefit from salinity management.

Resource Managers

The uses of the resources of the Colorado River are quite broad, ranging from water supply to power generation to recreational fisheries. Numerous federal, interstate, state, and local resource management agencies share responsibility for the effective management of these resources. Federal agencies including the Department of the Interior (the Bureau of Reclamation, Bureau of Land Management, and the Fish and Wildlife Service), the Department of Agriculture, U.S. Environmental Protection Agency and the Army Corps of Engineers are involved in management of the Colorado River's resources. The Department of State represented by the International Boundary and Water Commission becomes involved when Mexico's interests are at stake.

The various water resource management and water quality regulatory agencies of the basin states are also primary players in Colorado River salinity management. In 1974, the Basin states established the Colorado River Basin Salinity Control Forum for the purpose of interstate cooperation and to provide the states with the information necessary to comply with the Clean Water Act as amended. The Forum is comprised of representatives appointed by the governor from each of the seven Basin states. It provides a formal means for many of the stakeholders to discuss and influence Colorado River salinity management policy. The Colorado River Basin Salinity Control Advisory Council was created by Public Law 93-320 and acts as liaison between the Secretaries of the Interior and Agriculture and the Administrator of the Environmental Protection Agency and the states to control salinity. The members of the Council are appointed by the governors of the Colorado River Basin states.


Interpretation by the EPA of Public Law 92-500, the 1972 amendments to the Federal Water Pollution Control Act, led to the adoption of numeric salinity criteria for the Colorado River. Through the Forum, the states' acceptance of the criteria at three locations on the Lower Colorado River was accomplished.

The numeric criteria were adopted by each of the basin states, along with a salinity control program. Subsequently, the states' action was approved by the EPA. To meet these criteria, the Colorado River Salinity Control Program (Program) was developed. Without the Program, it is projected that Colorado River salinity would gradually limit use of the river for most M&I and agricultural purposes (see Figure 4). The plan of implementation for the Program recognizes that the Forum, participating federal agencies, and the Basin states each have specific responsibilities to further the Program. The overall strategy is to prevent salts from dissolving and mixing with the river's flow. This includes the interception and control of non-point sources such as surface runoff, as well as point sources such as wastewater discharges and saline hot springs. Congressional actions have Specified responsibilities for the Department of the Interior and Department of Agriculture establishing projects and programs to manage the salinity, including salinity contributed by federal lands, with substantial cost sharing with state and local government entities. In all cases, cost-effectiveness is a primary tenet of the Program-that is, getting the greatest reduction in salinity concentration for the amount of money spent.

Figure 4


The Program looks at salinity management within an approximate 20-year planning window, currently to 2015. An important element is periodic assessment as to whether implementation of the Program will maintain salinity concentration at or below the numeric criteria with average runoff. This will be accomplished by implementing projects that control salt contributions to the river from existing sources and minimize future increases in the salt load. Specific efforts include:

  • Implementation of cost-effective salinity control measures by Reclamation, BLM, and USDA.
  • Implementation of Forum-approved policies concerning point-source discharges regulated by the NPDES permit program, use of brackish or saline waters for municipal and industrial purposes, and use of the NPDES permit program to manage salinity from contributions by intercepted groundwater sources and by limiting salt contributions from fish hatcheries; and
  • Implementation of non-point source management plans.


In recognition of the federal role and responsibility to control the salinity of the Colorado River, P.L. 93-320 adopted a cost-sharing formula to fund the control measures. It is based in large part on the fact that significant tracts of federal land contribute substantially to the salinity of the Colorado River. This formula was subsequently modified in 1984 by amendments to P.L. 93-320, and currently calls for 70 percent federal funding with Department of the Interior salinity control funds. The remaining 30 percent is to come from the Upper and Lower Basin funds, which derive their revenues from hydropower generation. With the passage of P.L. 104-127, on-farm salinity control projects are to be funded from the USDA's Environmental Quality Incentives Program. Measures receiving such funding have proven to be among the most cost-effective components of the Program in recent years. The management of federal lands to reduce salt contributions is funded through and administered by the BLM and there is no cost-sharing contribution. Each year, the Basin States urge Congress to appropriate the funds necessary to implement the federal portions of the Program. From 1991 through 1994, the federal funding commitment averaged $46.1 million annually. In 1995, this dropped to less than half or $21.5 million, and in 1996 it declined to about $17 million.


Existing salinity control measures are preventing the contribution of about 0.62 million tons of salt per year, as measured at Hoover Dam. However, in order to maintain the salinity concentration at or below the required criteria level, measures should be in place to remove 1.04 million tons today, meaning there is a current shortfall of almost 0.42 million tons per year of salinity control. By 2015, with projected increased use of the Colorado River's resources, the need for salinity control will increase to require the control of 1.48 million tons annually. When including the current shortfall, this represents a need to increase salinity control by about 0.86 million tons per year today's level.


In short, the support of the Congress is urgently needed to maintain the ongoing ability to meet the goals of the Colorado River Salinity Control Program. The Program is a carefully designed series of sequentially staged elements that are only implemented as needed. Given the lead time necessary to accomplish many of these measures, funding must be secure to ensure that they are in place when required. Due to the well-recognized federal role in the Colorado River Basin, it is essential that the federal commitment to the Program continue to be supported by adequate funding of the elements of the Program, thereby honoring the Federal Government's responsibility as a partner in the protection of the Colorado River Basin's water quality.

Colorado River Basin
Salinity Control Forum
106 West 500 South, Suite 101
Bountiful, Utah 84010
Jack Barnett, Executive Director

   Citizen    Government    Business    Visitor   Privacy Policy