Missouri River Basin Water Management

A warm February led to increased snowmelt and runoff in the Missouri River Basin above Sioux City, Iowa. February runoff was 1.8 million acre-feet, 161% of average with above average runoff in every reach except Sioux City, which was near average. However, the updated 2024 calendar year runoff forecast for the basin continues to be below average.

January runoff in the Missouri River Basin above Sioux City was 0.4 million acre-feet, 56% of average. Runoff was well-below-average due to much-below-normal temperatures over the whole Missouri River Basin and below-normal precipitation over most of the upper basin. The 2024 calendar year runoff forecast above Sioux City is 18.8 MAF, 73% of average. The runoff forecast is based on current soil moisture conditions, plains snowpack, mountain snowpack, and long-term precipitation and temperature outlooks.

As the colder, winter temperatures enter the basin, USACE will closely monitor Missouri River ice conditions between the System reservoirs and downstream of Gavins Point Dam for potential ice jams that could impact river stages and water intakes. Runoff in the upper Missouri River Basin above Sioux City, Iowa, was 1.1 million acre-feet (MAF) during November, 107% of average. The 2023 calendar year runoff forecast is 29.9 MAF, 116% of average. Average annual runoff is 25.7 MAF.

Rainfall in the Missouri River Basin above Sioux City, Iowa, was above normal for August, resulting in above average runoff. However, due previous years' drier-than-normal conditions leaves the total storage in the Missouri River mainstem reservoir system below normal. Based on the Sept. 1 system storage, Gavins Point Dam winter releases will be 13,000 cfs, per the Master Manual criteria. This call focuses on winter release rates and storage at Fort Peck meeting the criteria for a planned Test Flow.

Above average rainfall and fast-melting snow led to above average runoff in the upper Missouri River Basin in June. Runoff above Sioux City, Iowa was 6.7 million acre-feet, which is 122% of average. The annual runoff forecast above Sioux City, Iowa is 29.2 MAF, 114% of average, and about 2.4 MAF higher than last month’s forecast. Precipitation was normal to much-above-normal for the month of June in much of Montana, southern and east-central North Dakota, and western South Dakota. Below-normal precipitation occurred in eastern South Dakota and into the lower Basin.

Warm temperatures in the mountainous region of the upper Missouri River Basin has led to a quick melt of the mountain snowpack. The rapid melting combined with precipitation in the western half of the Basin resulted in above-average inflow into the reservoir system. May runoff for the Basin above Sioux City, Iowa was 4.9 million acre-feet, 144% of average. "The warm temperatures in the northern Rockies has melted the snow earlier than is typical,” said John Remus, chief of the U.S. Army Corps of Engineers’ Missouri River Basin Water Management Division. “With much of the mountain snowpack already melted, the Basin will need additional rainfall to continue the trend of above-average runoff.”

Late season plains snowpack accumulation and subsequent melting led to increased runoff throughout the upper Missouri River Basin during April. For the month, runoff was 4.7 million acre-feet, 159% of average, for the basin above Sioux City, IA. The annual runoff forecast for the upper Missouri River Basin above Sioux City, IA is 26.9 MAF, 105% of average, and 0.5 MAF higher than last month’s forecast. However, soil moisture remains slightly below normal in eastern Montana and the western Dakotas, and well below normal in Nebraska. Even with the plains snowmelt, soils dried out in late April over a large portion of the upper basin.

The updated 2023 calendar year runoff forecast for the Missouri River Basin above Sioux City, Iowa, continues to be below average. The 2023 calendar year runoff forecast above Sioux City is 21.5 million acre feet, 84% of average. The runoff forecast is based on current soil moisture conditions, plains snowpack, mountain snowpack, and long-term precipitation and temperature outlooks. February runoff in the Missouri River Basin above Sioux City was 1.0 MAF, 86% of average.

The updated 2023 calendar year runoff forecast for the Missouri River Basin above Sioux City, Iowa, continues to be below average. The 2023 calendar year runoff forecast above Sioux City is 21.1 MAF, 82% of average. The runoff forecast is based on current soil moisture conditions, plains snowpack, mountain snowpack, and long-term precipitation and temperature outlooks.

For the 2022 calendar year, Missouri River basin runoff above Sioux City, Iowa totaled 19.3 million acre-feet, 75% of average. This was the 30th lowest annual runoff for the Missouri River Basin in 125 years of record-keeping. The ongoing drought shows little relief in sight and the U.S. Army Corps of Engineers predicts runoff into the mainstem reservoir system will remain below normal. For 2023, runoff in the Missouri River basin above Sioux City, Iowa is forecast to be 20.8 MAF, 81% of average.

The September update shows drought conditions in the Missouri River Basin above Sioux City, Iowa, continued throughout August. Per the Master Manual and the September 1 System storage check, winter releases from Gavins Point Dam will be 12,000 cubic feet per second (cfs), as part of the overall water conservation measures. August runoff was 0.9 MAF, 62% of average above Sioux City, and 0.6 MAF or 49% of average above Gavins Point Dam. The portion of the basin that drains into Oahe Reservoir was particularly dry, only experiencing 10% of its average August runoff. The 2022 calendar year forecast for the upper Basin, updated on September 1, is 20.2 million acre-feet (MAF), 78% of average. Average annual runoff for the upper Basin is 25.8 MAF.

This extended water management call includes an update on the Missouri River mainstem reservoir system operations as well as from the Omaha District Drought coordinator. While the Missouri River basin has seen improved runoff for two consecutive months, it is not enough to overcome the long-term drought persisting in much of the basin. July runoff in the Missouri River basin above Sioux City, Iowa was 3.2 million acre-feet, which is 98% of average and 0.7 MAF more than was forecast last month. This has led to an annual runoff forecast of 20.6 MAF, which is 80% of average and 0.6 MAF higher than last month’s forecast.

Water management calls include an update from the NOAA and the NWS's Missouri Basin River Forecast Center, as well as an update on Missouri River mainstem reservoir system operations. Despite improved runoff in June, conservation measures will continue for the second half of the navigation flow support season based on the July 1 Missouri River Mainstem Reservoir System storage. June runoff in the Missouri River basin above Sioux City, Iowa was 5.2 million acre-feet, 94%of average. The updated 2022 runoff forecast is 20.0 MAF, 78% of average and 1.7 MAF higher than last month’s annual runoff forecast. June runoff into Garrison was 110%of average.

Water management calls include an update from the NOAA and the NWS's Missouri Basin River Forecast Center, as well as an update on Missouri River mainstem reservoir system operations. Runoff continues to be below average in the upper Missouri River Basin above Sioux City, Iowa. The updated 2022 runoff forecast is 18.3 MAF, 71% of average and 0.5 MAF higher than last month’s annual runoff forecast. If realized, this runoff amount would rank as the 25th lowest calendar year runoff since 1898.

Water management calls include an update from the NOAA and the NWS's Missouri Basin River Forecast Center, as well as an update on Missouri River mainstem reservoir system operations. Dry conditions in April resulted in well-below average runoff in the upper Missouri River Basin. April runoff was 1.5 million acre-feet, which is 51% of average. The updated 2022 upper Basin runoff forecast is 17.8 MAF, 69% of average, which, if realized, would rank as the 23rd lowest calendar year runoff volume.

The updated 2022 calendar year runoff forecast for the Missouri River Basin above Sioux City, Iowa, continues to be below average. Runoff in February was less than predicted, and lower-than-average runoff is expected to continue in the coming months. Snow accumulation in the plains and the mountains continues to be below average, and the soil moisture remains very low compared to normal. The 2022 calendar year runoff forecast above Sioux City, Iowa, has dropped from 21.7 million acre feet last month to 20.4 MAF on March 1, a reduction of 1.3 MAF. If realized, this forecast would be 79% of normal.

The USACE Missouri River Water Management Division held its monthly update call on Thursday, Feb. 3 to discuss current conditions, and the projected operation of the mainstem reservoir system. January’s runoff was slightly above average but 2022's runoff is expected to remain below average with plains and mountain snowpack lagging behind seasonal averages, and soil moisture much drier-than-normal.

The USACE Missouri River Water Management Division held its first monthly update call of 2022 on Thursday, Jan. 6 to discuss current conditions, and the projected operation of the mainstem reservoir system. The 2021 calendar year runoff summation for the Missouri River basin above Sioux City, Iowa was 15.2 million acre-feet, 59% of average and the 10th lowest annual runoff for the in 123 years of record-keeping. No callers asked questions.

The USACE Missouri River Water Management Division held its monthly update call on Thursday, Aug. 5 to discuss current conditions, and the projected operation of the mainstem reservoir system. The July 8 recording had technical issues. Below-average precipitation and dry soil conditions persist in the upper Missouri River Basin above Sioux City, Iowa. The updated 2021 upper Basin runoff forecast is 14.6 million acre-feet, 57% of average. If realized, this runoff amount would be in the 10th driest year in the upper Basin since 1898.

The USACE Missouri River Water Management Division held its monthly update call on Thursday, June 3 to discuss current conditions, and the projected operation of the mainstem reservoir system. Below-average precipitation and dry soil conditions persist in the upper Missouri River Basin above Sioux City, Iowa. The updated 2021 upper Basin runoff forecast is 17.9 million acre-feet, 69% of average. If realized, this runoff amount would be in the 22nd driest year in the upper Basin since 1898.