Missouri River Basin Water Supply Statement

Missouri Basin River Forecast Center
Water Supply Statement
Issued in cooperation with the Natural
Resources Conservation Service
Issued:  June 30, 2026

 Upper Missouri Basin

May precipitation across the Upper Missouri Basin was below average. Precipitation summaries  include: Milk St. Mary, 94 percent; Milk Canada, 104 percent; Lower Milk, 59 percent;
above Toston, 54 percent; Toston to Ft. Peck, 73 percent.

May 2026 Upper Missouri Mean Precip                                  Oct-May WY2026 Upper Missouri Mean Precip

Of the four major irrigation reservoirs in Montana; Lima
Reservoir had 87 percent average storage, Clark Canyon was
holding 69 percent of average water, Gibson Reservoir had 105
percent of average stored water, and Fresno Reservoir had
43 percent of average stored water.


Yellowstone Basin 

Precipitation during May was below average. The upper Yellowstone 
River Basin received 64 percent of average precipitation while the Lower 
Yellowstone River Basin reported 53 percent of average. The Bighorn 
Basin received 49 percent of average precipitation while the
Wind River Basin received 56 percent of average. The Little Bighorn -
Upper Tongue Basin received 56 percent of average and the Powder River
had 40 percent of average precipitation.

 May 2026 Yellowstone Mean Precip                                        Oct-May WY2026 Yellowstone Mean Precip

 

Month end storage at Boysen Reservoir was 96 percent of average. 
Stored water in Buffalo Bill Reservoir was 107 percent of average. 
Month end storage was 92 percent of average at Bighorn Reservoir.

 

Platte Basin 

Precipitation during May in the Upper North Platte Basin was 119
percent of average.  In the Lower North Platte Basin, precipitation
was 89 percent of average.  The North Platte Plains below Guernsy
Reservoir had 53 percent.  The South Platte Mountains had 114
percent whereas the Plains had 81 percent of average May
precipitation.

 

 May 2026 Platte Mean Precip                                            Oct-May WY2026 Platte Mean Precip

Stored water in the South Platte Basin was 90 percent of average
on June 1.

PRECIPITATION MAPS

May 2026	WY 2026
May 2026 Precipitation Percent of 1991-2020 Average	WY2026 Precipitation as Percent of 1991-2020 Average
May 2026 Basin Mean Precipitation	WY2026 Basin Mean Precipitation
May 2026 MBRFC Basin Mean Precipitation	WY2026 MBRFC Basin Mean Precipitation