Corps Updates Missouri River Basin Conditions

The Army Corps of Engineers held five public meetings in April to discuss expected runoff into the Missouri River reservoir system. The Missouri River basin covers over 529,000 square miles (one-sixth of the continental United States). Only 279,000 square miles of the basin are regulated by the six mainstem reservoirs. As of April 10, there was 58.7 million acre feet (maf) of water stored in system, including 2.6 maf in the flood control and multiple use zone. The reservoir system can hold 72.8 maf, so there is plenty of storage space available this year. (An acre foot is the amount of water needed to cover an acre of land one foot deep.)

The Corps expects the 2017 runoff above Sioux City to be 29.4 maf. That’s 116% of the annual average of 25.3 maf. The slightly higher runoff is attributed to this year’s mountain snowpack. The amount of snow was 93% of the annual average above Fort Peck Dam in Montana and 136% of the average in the area between Fort Peck and Garrison Dam in North Dakota.

The water from the mountain snowpack is expected to increase the reservoir system levels to 62 maf in July. That should mean rising water levels in the reservoirs in Montana, North, and South Dakota, which will benefit forage and game fish reproduction and keep boat ramps accessible.