As hot and dry as conditions have been throughout the central and western portions of the United States this summer, it should not come as a complete surprise that the amount of runoff projected to enter the Missouri River system has been lowered once again.
According to the August projections supplied by the U.S. Army Corps of Engineers, even massive Lake Sakakawea will not be spared from losing more elevation in the coming months than was previously forecast.
Lake Sakakawea's Monday elevation was 1,836.9 feet. The lake is now projected to drop to 1,835.3 feet by the end of August and to 1,833.3 by the end of 2012. That compares to the July outlook of an expected elevation of 1,834.3 on Dec. 31, 2012.
A rocky point is exposed on Lake Sakakawea. Although water levels are considered good on Lake Sakakawea today, the reservoir is expected to decline through the end of the year. Runoff next spring and summer could prove crucial to replenishing Lake Sakakawea and other Missouri River reservoirs.
"Basin conditions grew worse last month with many areas in the basin transitioning into more severe drought conditions," said Jody Farhat, Chief of the Corps' Missouri Water Management Division in Omaha, Neb.
Total runoff into the basin is now projected to be 21.0 million acre feet. July's outlook was 21.4 maf. Going back to March 2012, the runoff was projected at 26.1 maf. The downward revision reflects changing weather conditions within the basin. The Corps notes that heavy precipitation, or lack of precipitation, in the coming weeks could cause further adjustments in the runoff data.
While the sheer size of Lake Sakakawea helps to buffer it from even a more drastic decline than forecast, other reservoirs in the system are about to undergo significant changes. According to the Corps, "to continue to support downstream navigation flows on the Missouri River, the Corps has been gradually increasing releases out of Gavins Point Dam."
Gavins Point, located in Nebraska, is the final reservoir on the Missouri prior to its juncture with the Mississippi River. Moving upstream, in order, is Fort Randall, Big Bend and Lake Oahe; all in South Dakota. Lake Sakakawea, or Garrison Reservoir, is the next upstream reservoir. Further upstream is Montana's Fort Peck Reservoir, the first major reservoir on the Missouri.
Releases from Gavins Point are scheduled to be increased to 38,000 cubic feet per second by Aug. 10. Fort Randall releases will be increased from 32,400 cfs in July to an average of 36,900 in August. Big Bend will increase from 31,900 cfs to 38,100 cfs during the same period.
Lake Oahe, of which a major portion is in North Dakota, will see an increase from an average release of 31,900 cfs in July to an average 38,100 in August. The effect, says the Corps, will be a drop of 3.5 feet in elevation on Lake Oahe in August.
Garrison releases are scheduled to remain at 24,500 cfs in August, virtually no change from the July release rate. However, Lake Sakakawea is projected to lose 1.9 feet of water by the end of August.
None of the projected elevations, in the short term, are considered unusually low. However, if conditions continue as projected, the Missouri River system reservoirs will begin 2013 in need of normal or above normal runoff next spring and summer to rise to what is considered normal operating levels.