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:  September 16, 2021


 Upper Missouri Basin

August precipitation across the Upper Missouri Basin was above average. Basin precipitation summaries for the Missouri Basin include: Milk St. Mary, 163 percent; Milk Canada, 122 percent; Lower Milk, 161 percent; above Toston, 133 percent; Toston to Ft. Peck, 153 percent. 

Of the four major irrigation reservoirs in Montana; Lima Reservoir had 70 percent average storage, Clark Canyon was holding 58 percent of average water, Gibson Reservoir had 21 percent of average stored water, and Fresno Reservoir had 74 percent of average stored water.

Yellowstone Basin 

Precipitation during August was above average. The upper Yellowstone River Basin received 189 percent of average precipitation while the Lower Yellowstone River Basin reported 169 percent of average. The Bighorn Basin received 212 percent of average precipitation while the Wind River Basin received 175 percent of average. The Little Bighorn - Upper Tongue Basin received 182 percent of average and the Powder River had 111 percent of average precipitation.

Monthend storage at Boysen Reservoir was 110 percent of average. Stored water in Buffalo Bill Reservoir was 113 percent of average. Monthend storage was 89 percent of average at Bighorn Reservoir.


Platte Basin 

Precipitation during August in the Upper North Platte Basin was 126 percent of average.  In the Lower North Platte Basin, precipitation was 100 percent of average.  The North Platte Plains below Guernsy Reservoir had 67 percent.  The South Platte Mountains had 60 percent whereas the Plains had 27 percent of average August precipitation.

Stored water in the South Platte Basin was 119 percent of average on September 1.


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