Missouri River Basin Water Management

June runoff in the Missouri River Basin above Sioux City, Iowa was 3.3 million acre-feet, 60% of average. The updated 2025 calendar year runoff forecast for the Missouri River Basin above Sioux City, Iowa, is 19.1 MAF, 74% of average, and slightly lower than last month’s forecast. The runoff forecast is based on current soil moisture conditions, mountain snowpack, and long-term precipitation and temperature outlooks.

The June 2025 calendar year runoff forecast for the Missouri River Basin above Sioux City, Iowa, continues to be below average. “Heavy rainfall in western and central North Dakota and South Dakota during May supplemented the mountain snowmelt runoff,” said John Remus, chief of the U.S. Army Corps of Engineers’ Missouri River Basin Water Management Division.

The updated 2025 calendar year runoff forecast for the Missouri River Basin above Sioux City, Iowa, continues to be below average. April runoff in the Missouri River Basin above Sioux City was 1.4 million acre-feet, 48% of average. “Runoff into the reservoir system was below average for the month of April, and runoff was below average in all reaches,” said John Remus, chief of the U.S. Army Corps of Engineers’ Missouri River Basin Water Management Division. “Drought or abnormally dry conditions are currently present in 75% of the basin, and conditions have worsened in the Fort Peck reach and parts of the Garrison reach in the last month. As a result, the runoff forecast was lowered by 1.9 MAF from last month.”

The 2025 calendar year runoff forecast above Sioux City is 22.1 MAF, 86% of average. The runoff forecast is based on current soil moisture conditions, plains snowpack, mountain snowpack, and long-term precipitation and temperature outlooks. Average is 25.7 MAF. The March 3 mountain snowpack in the Fort Peck reach was 89% of average, while the mountain snowpack in the Fort Peck to Garrison reach was 91% of average. By March 1, about 79% of the total mountain snowfall has typically accumulated. Mountain snow normally peaks near April 17.

The updated 2025 calendar year runoff forecast for the Missouri River Basin above Sioux City, Iowa, continues to be below average. January runoff in the Missouri River Basin above Sioux City was 0.7 million acre-feet, 92% of average. Runoff was near or below average for most of the Missouri River Basin, and most of the upper basin had below-normal precipitation.

For the 2024 calendar year, Missouri River basin runoff above Sioux City, Iowa totaled 23.3 million acre-feet, 91% of average. Dry conditions continue to affect the upper Missouri River Basin at the start of the 2025 calendar year, so the U.S. Army Corps of Engineers is forecasting below-average runoff into the mainstem reservoir system. For 2025, runoff in the Missouri River basin above Sioux City, Iowa is forecast to be 20.2 MAF, 79% of average.

Drought is present across 73% of the Basin. August runoff was 1.2 MAF, 86% of average above Sioux City. The updated upper Basin runoff forecast for is 23.8 MAF, 92% of average. On Sept. 1, the volume of water stored in the System was 55.1 MAF, or 1.0 MAF below the base of the flood control zone. Storage is expected to decline through the fall. Expect System storage to be about 4.7 MAF below the base of flood control zone at the start of the 2025 runoff season

July runoff in the Missouri River basin above Sioux City, Iowa was 2.8 million acre-feet, 85% of average with below-average runoff in the upper three reaches and above-average runoff in the lower three reaches. The annual runoff forecast above Sioux City, Iowa is 23.9 MAF, 93% of average. “July brought warmer and drier weather to the Missouri River Basin,” said John Remus, chief of the U.S. Army Corps of Engineers’ Missouri River Basin Water Management Division.

This is the final call of the 2024 flow test. The average daily release rate from Fort Peck is 8,000 cfs and monitoring of pallid sturgeon continues. However, there is no indication of spawning therefore a drift flow was not undertaken. An update on the Wolf Point and Culbertsn gauges was provided. Monitoring of the from the test such as pool levels, erosion, dam safety, etc., will continue once the test is complete later this fall.

The average daily release rate from Fort Peck is 8,000 cfs and monitoring of pallid sturgeon continues. Irrigators asked about the Wolf Point gauge and USACE will be talking to the USGS to get more information on the gauge. Monitoring of the from the test such as pool levels, erosion, dam safety, etc., will continue once the test is complete later this fall.