The water level in Lake Sakakawea continues to decline, even more so than what has been anticipated in a hot and dry summer. The latest runoff forecast for the Missouri River Basin, as determined by the U.S. Army Corps of Engineers, is 14.6 million acre feet of water. That compares to a historic average of 25.8 maf and is down 1-million acre feet from a month earlier.
The numbers throughout the Missouri River Basin are attention getting, albeit not for the best of reasons. Upper Basin runoff during July reached only 34% of average, for the year just 57% of normal. The July runoff into Fort Peck Reservoir in Montana was the lowest recorded in 123 years. Sakakawea’s runoff input in July was just 24% of the long-term average. 57% of normal runoff for 2021 would be the driest year in the upper basin since 1898.
The result, quite predictably, is dropping water levels throughout the mainstream reservoirs on the Missouri River system. The downward trend is easily visible along the shoreline of Lake Sakakawea where the distance from the top of the bank to the water below continues to grow each day. So too does the walk from the bottom of boat ramps to the parking areas above.
In July Sakakawea lost 1.8 feet of water, an amount that will likely be very similar in August. Lake Sakakawea stood at 1,834.4 feet Thursday, down more than 10 feet from a year ago and down 18 feet from the same time in 2019. The latest projections provided by the Corps anticipate a level of 1,832.6 at the end of August with a continuing decline to 1,827.9 feet by the end of the year.
A usual goal for Lake Sakakawea water management is to have the reservoir be no higher than 1,837.5 feet at the end of February, which is the top of the Carryover Multiple Use Zone. According to the latest outlook the end of February, 2022 level of Lake Sakakawea is projected to be 1,827.6 feet. The last time that level was reached was February 2009.
While the water level of Lake Sakakawea is down and declining, it is not too far out of the norm for the sprawling reservoir that has experienced great fluctuations in water levels since construction was completed on the reservoir in 1955. However, the last similar period of low water occurred from 2001-2008 when Lake Sakakawea was under 1,820 feet at the end of August for five of those eight years.
What is most concerning now is how much snow will fall over the drainage this coming winter and how much runoff will occur. Snowmelt runoff is the biggest contributor to the amount of water entering Lake Sakakawea each spring and summer. Without significant runoff in 2022 Lake Sakakawea could see another year of declining water levels.
Power generation from the six mainstem power plants on the Missouri River reservoirs, including the Garrison Dam Power Plant, is expected to be 8.7-billion kWh this year. The long-term average is 9.5-billion kWh.