Rain brings much-needed relief to Missouri Basin Rain across the entire Missouri River basin and late-season snow in the mountains in May brought much needed relief from the unrelenting drought. The precipitation, combined with Army Corps of Engineers conservations measures, raised reservoir levels one to two feet during the critical fish spawning period.
The levels of the three big reservoirs in Montana, North Dakota and South Dakota each rose in May, setting up good water conditions for a successful spawn of both game and forage fish. Last month�s runoff was 1.1 million acre feet (MAF).
�The continuing drought is having profound impacts throughout the basin. The Corps has taken a number of initiatives to ease these impacts� said Larry Cieslik, chief of the Water Management Office in Omaha, NE. Navigation targets at Sioux City, IA were not met in April or May. Efforts to maintain steady to rising reservoir levels to aid the spring fish spawn in the Oahe and Fort Peck reservoirs were successful. The rain and snow raised Garrison two feet. Boat ramps have been extended and relocated at each of the reservoirs to maintain access to the water. Municipal water intakes in North Dakota nd South Dakota are being closely monitored.
�We are forecasting this year�s runoff will be 16.6 MAF. Under the Basic computer simulation, the navigation season could be shortened 61 days under the Revised Master Manual and its more stringent drought conservation measures,� said Cieslik. A final determination of the navigation season length will be made after the water-in-storage check on July 1. Normal runoff is 25.2 MAF.
Releases from Gavins Point Dam in May averaged 21,200 cubic feet per second (cfs), compared to a long-term average of 29,800 cfs. They may be gradually increased from the current 23,000 cfs if needed to meet minimum downstream flow targets.
The mountain snowpack above Fort Peck crested on April 22 at 76 percent of normal. The snowpack in the reach from Fort Peck to Garrison peaked on May 13 at only 73 percent of normal.
Runoff from the remaining mountain snow will continue entering the reservoirs for a few more weeks. System storage ended May at 36.1 MAF, up 800,000 acre feet during the month. The amount of water in the reservoirs is more than 22 MAF below normal for this time of year.
Gavins Point reservoir will remain essentially level at elevation 1206 feet msl during June.
Fort Randall Dam releases averaged 18,800 cfs in May. They will range from 15,000 cfs to 23,000 cfs in June as needed to maintain Gavins Point reservoir near its desired elevation. Fort Randall reservoir ended May at 1354.6 feet msl, where it will remain through July.
Big Bend reservoir will remain at its normal elevation of 1420 feet. Releases will be adjusted to meet hydropower needs.
Oahe reservoir rose nearly two feet during May, ending the month at elevation 1576.5 feet msl. It will remain essentially level through June, ending the month 30.5 feet below average. The reservoir is 2 feet lower than last year at this time.
Garrison Dam releases averaged 16,500 cfs during May, compared to the average of 21,700 cfs. The reservoir rose more than two feet in May, ending the month at elevation of 1808.8 feet msl. It will continue to rise about half a foot through mid-month before gradually declining back to its current level on June 30. It will end the month 29 feet below average. The reservoir is 7 feet lower than last year at this time.
Fort Peck Dam releases averaged 5,400 cfs in May compared to the normal of 9,400 cfs. They will be held steady at 5,500 cfs in June to help the fish spawn and provide minimum flows for irrigators downstream of the dam. The reservoir rose one foot in May, ending the month at elevation of 2199.6 feet msl. It will remain essentially level through June, ending the month at 2200, 35 feet below average. Last year at this time it was 4 feet higher.
The six main stem powerplants generated 501 million kilowatt hours (kWh) of electricity in May, 61 percent of normal. The forecast for 2005 energy production of 5.6 billion kWh, compared to a normal of 10 billion kWh.