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, which is 48 percent of the average.
“Runoff into the reservoir system was below average for the month of April, and runoff was below average in all reaches,” says John Remus of the U.S. Army Corps of Engineers. “Drought or abnormally dry conditions are currently present in 75 percent of the basin, and conditions have worsened in the Fort Peck reach and Garrison reach in the last month, which resulted in a forecast lowered by 1.9 million acre-feet from last month.”
The 2025 calendar year forecast above Sioux City is 20 million acre-feet, 78 percent of the average. The runoff forecast is based on current soil moisture conditions, mountain snowpack, and long-term precipitation and temperature outlooks.
