High, low, and average or normal stream flow conditions were determined for each of the seven subbasins of the Platte River Basin. Stream flow gauges within the North and South Platte River Basins in Wyoming were located using the resources of the United States Geological Survey (USGS), Wyoming State EngineerÆs Office (SEO), and the Water Resources Data Systems (WRDS) library. Stream flow gauge data were then compiled to determine high, low, and average or normal annual flow years for each of the Platte Basin subbasins.

The process to determine and assess stream flow included:

• Identifying North and South Platte River stream flow gauges located in Wyoming that are not influenced by major reservoir operations and collecting gauge data;
• Selecting a potential period of study;
• Determining if the selected period of study satisfactorily represented the long term;
• Selecting representative index stream flow gauges for each subbasin within Wyoming's Platte River Basin; and
• Compiling and processing index stream flow gauge data to compare high, low, and normal or average stream flow years in each subbasin.

The "high flow year" designation was assigned to years having total annual gauged flows in the highest 20th percentile during the 1972 through 2001 study period or to the years having the highest annual flows followed by a significant decrease in annual flow. The "low flow year" designation was assigned to years having total annual gauged flows in the lowest 20th percentile during the study period. The "normal or average year" designation was assigned to the remaining years during the study period.

The representative stream flow gauge in the Lower Laramie River subbasin from which data were collected and assessed included:

• Laramie River infolow to Greyrocks Resevoir - WSEO

Click here to view a map of the representative stream flow gauge in the Lower Laramie River subbasin.

The following table summarizes the Lower Laramie River subbasin high, low, and normal stream flow years during the study period. Note that stream flow volumes may be used only to determine high, low, and normal or average stream flow years; composite stream flow volumes shown below do not indicate actual flows at any point in the subbasin.

Summary of representative annual high stream flow, low stream flow, and normal or average stream flow in the Lower Laramie subbasin

No.	Year	Annual stream flow (acre-feet)
1	1983	547,549
2	1984	379,341
3	1995	164,785
4	1986	156,246
5	1980	122,208
6	1999	86,231
7	1991	67,549
8	2000	55,271
9	1993	45,259
10	2001	41,821
11	1985	39,231
12	1988	36,411
13	1997	36,097
14	1996	34,019
15	1987	32,257
16	1982	24,462
17	1998	24,091
18	1981	22,604
19	1990	19,864
20	1994	19,753
21	1992	14,231
22	1989	14,069
		Indicates high flow year and flow volume
		Indicates low flow year and flow volume
Years and annual flows which are neither shaded or outlined are normal or average stream flow years and flows.