January 15, 2003

Drought draining Missouri River basin resources

he pool levels of the upper Missouri River's six main-stem dam reservoirs are continuing to decrease as current drought conditions persists in the northern Plains states. The three largest reservoirs, Lake Oahe in South Dakota, Lake Sakakawea in North Dakota and Fort Peck Lake in Montana hold 89 percent of all water stored in the six dam system. Each reservoir is lower than it was a year ago at this time. 

The amount of total water held in the six reservoirs has been reduced to 13 million acre-feet below average during the drought. These levels are not at record lows, but because of this winter's lack of moisture, pool levels are continuing to decrease at a time when they should at least be maintaining consistent levels, irregardless of current winter scaled-back release levels. 

Figures for the last full month, December 2002, show the reservoir system ended the month with 42.7 million acre-feet of total storage volume, this is 400,000 acre-feet below normal. As a reference, storage in the system peaked in July 2002 at 48.9 million acre-feet. Normal reservoir storage peak is 62 million acre-feet. 

The below-normal reservoir water storage reserves are also causing a reduction of the dam's hydropower production. In 2002, total hydroelectric power generated by the main-stem dam system was 7.5 billion kilowatt hours. This result was 2.7 billion kilowatt hours below "normal" expected output. December 2002's production ended up at only 69 percent of normal.  Hydroelectric production will continue to decrease if drought conditions persist. 

The winter of 2002 did not produce sufficient mountain snow pack and the plains experienced way below-normal spring and early summer rainfall precipitation. The Army Corps of Engineer's Missouri River Basin Water Management Division in Omaha estimated that the Missouri River's total basin runoff in 2002 was a historic 36 percent below normal contribution levels. Last year resulted in the 10th-lowest river basin runoff total since 1898! As of Jan 2 mountain snow pack was 58% of normal in the Montana reach above Fort Peck reservoir and 74% in the reach from Fort Peck Dam, down to lake Sakakawea and Garrison Dam in South Dakota.

Low water flows could affect the Missouri River's coming 2003 navigation season, which begins April 1st. Evidence of lower than normal winter river water levels can be seen by viewing the riverbank at any location near the Omaha-Council Bluffs area. The river is presently running at about 2 foot below normal winter stage. 

The declining river is being shadowed by the increasing exposure of rock dikes, pilings, dry jettys and ever-higher mud banks. Normal off-navigation winter Gavins Point dam release rates are usually 13 to 14,000 cubic-foot per-second (cfs). 

Gavins Point discharge averaged approximately 12,000 cfs during the last full month of December 2002, hence the lower river levels and more prominent sandbars, a direct result of the minimal releases and drought-stricken tributaries south of Lewis and Clark Lake.

Missouri River basin runoff projections are grim, even though the biggest snowfall months in the Montana mountains are yet to come. Flow support is expected to be at very minimal levels when the Missouri's navigation season begins April 1 at the river's mouth near St. Louis, MO.