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:  August 19, 2023


 Upper Missouri Basin

July precipitation across the Upper Missouri Basin was below average. Basin precipitation summaries for the Missouri Basin include: Milk St. Mary, 56 percent; Milk Canada, 28 percent; Lower Milk, 50 percent; above Toston, 47 percent; Toston to Ft. Peck, 43 percent. 

Of the four major irrigation reservoirs in Montana; Lima Reservoir had 153 percent average storage, Clark Canyon was holding 129 percent of average water, Gibson Reservoir had 66 percent of average stored water, and Fresno Reservoir had 80 percent of average stored water.

Yellowstone Basin 

Precipitation during July ranged from below to near average. The upper Yellowstone River Basin received 79 percent of average precipitation while the Lower Yellowstone River Basin reported 46 percent of average. The Bighorn Basin received 105 percent of average precipitation while the Wind River Basin received 94 percent of average. The Little Bighorn - Upper Tongue Basin received 87 percent of average and the Powder River had 96 percent of average precipitation.

Monthend storage at Boysen Reservoir was 101 percent of average. Stored water in Buffalo Bill Reservoir was 99 percent of average. Monthend storage was 97 percent of average at Bighorn Reservoir.


Platte Basin 

Precipitation during July in the Upper North Platte Basin was 89 percent of average.  In the Lower North Platte Basin, precipitation was 112 percent of average.  The North Platte Plains below Guernsy Reservoir had 121 percent.  The South Platte Mountains had 85 percent whereas the Plains had 129 percent of average July precipitation.

Stored water in the South Platte Basin was 122 percent of average on August 1.


July 2023  WY 2023
July 2023 Precipitation Percent of 1981-2010 Average WY2023 Precipitation as Percent of 1981-2010 Average
July 2023 Basin Mean Precipitation          WY2023 Basin Mean Precipitation
July 2023 MBRFC Basin Mean Precipitation      WY2023 MBRFC Basin Mean Precipitation