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:  June 23, 2023



 Upper Missouri Basin

May precipitation across the Upper Missouri Basin ranged from below to above  
average.  Basin precipitation summaries for the Missouri Basin include: Milk St. Mary,
51 percent; Milk Canada, 54 percent; Lower Milk, 123 percent; above Toston,
67 percent; Toston to Ft. Peck, 112 percent. 


May 2023 Upper Missouri Mean Precip                                  Oct-May WY2023 Upper Missouri Mean Precip


Of the four major irrigation reservoirs in Montana; Lima
Reservoir had 115 percent average storage, Clark Canyon was
holding 94 percent of average water, Gibson Reservoir had 108
percent of average stored water, and Fresno Reservoir had
103 percent of average stored water.

Yellowstone Basin 

Precipitation during May was below to above average. The upper Yellowstone 
River Basin received 69 percent of average precipitation while the Lower 
Yellowstone River Basin reported 135 percent of average. The Bighorn 
Basin received 77 percent of average precipitation while the
Wind River Basin received 68 percent of average. The Little Bighorn -
Upper Tongue Basin received 96 percent of average and the Powder River
had 108 percent of average precipitation.

 May 2023 Yellowstone Mean Precip                                        Oct-May WY2023 Yellowstone Mean Precip

Month end storage at Boysen Reservoir was 112 percent of average. 
Stored water in Buffalo Bill Reservoir was 111 percent of average. 
Month end storage was 98 percent of average at Bighorn Reservoir.


Platte Basin 

Precipitation during May in the Upper North Platte Basin was 42
percent of average.  In the Lower North Platte Basin, precipitation
was 87 percent of average.  The North Platte Plains below Guernsy
Reservoir had 158 percent.  The South Platte Mountains had 192
percent whereas the Plains had 221 percent of average May


 May 2023 Platte Mean Precip                                            Oct-May WY2023 Platte Mean Precip


Stored water in the South Platte Basin was 107 percent of average
on June 1.


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