National Weather Service United States Department of Commerce

Missouri Basin River Forecast Center
Water Supply Statement
Issued in cooperation with the Natural
Resources Conservation Service
Issued:  July 21, 2021


 Upper Missouri Basin

June precipitation across the Upper Missouri Basin was below average. Basin precipitation summaries for the Missouri Basin include: Milk St. Mary, 42 percent; Milk Canada, 19 percent; Lower Milk, 48 percent; above Toston, 13 percent; Toston to Ft. Peck, 25 percent. 

Of the four major irrigation reservoirs in Montana; Lima Reservoir had 74 percent average storage, Clark Canyon was holding 74 percent of average water, Gibson Reservoir had 108 percent of average stored water, and Fresno Reservoir had 75 percent of average stored water.

Yellowstone Basin 

Precipitation during June was below average. The upper Yellowstone River Basin received 18 percent of average precipitation while the Lower Yellowstone River Basin reported 24 percent of average. The Bighorn Basin received 30 percent of average precipitation while the Wind River Basin received 49 percent of average. The Little Bighorn - Upper Tongue Basin received 25 percent of average and the Powder River had 39 percent of average precipitation.

Monthend storage at Boysen Reservoir was 113 percent of average. Stored water in Buffalo Bill Reservoir was 122 percent of average. Monthend storage was 88 percent of average at Bighorn Reservoir.


Platte Basin 

Precipitation during June in the Upper North Platte Basin was 46 percent of average.  In the Lower North Platte Basin, precipitation was 68 percent of average.  The North Platte Plains below Guernsy Reservoir had 51 percent.  The South Platte Mountains had 97 percent whereas the Plains had 62 percent of average June precipitation.

Stored water in the South Platte Basin was 112 percent of average on July 1.


June 2021  WY 2021
June 2021 Precipitation Percent of 1981-2010 Average WY2021 Precipitation as Percent of 1981-2010 Average
June 2021 Basin Mean Precipitation          WY2021 Basin Mean Precipitation
June 2021 MBRFC Basin Mean Precipitation      WY2021 MBRFC Basin Mean Precipitation