Army Corps cranks up water releases on Missouri River dams to double the previous record

[phantom power]

Six flood control dams lie on the Missouri River between eastern Montana and Sioux City, Iowa; these dams were built between 1940 and 1964. As water from this spring's record precipitation have flowed into the Missouri River basin, the reservoirs behind these dams have risen to record levels. On May 31, the Army Corps of Engineers was forced to open the the spillway gates on the massive Garrison Dam, 50 miles northwest of Bismark, North Dakota. It was the first time since the dam was built in 1955 that the spillway gates were opened. (Remarkably, during 2007 and early 2008, Lake Sakakawea water levels behind Garrison Dam were the lowest since the dam was built--46 feet below the current level--thanks to a decade-long drought.) On June 3, as the record flood progressed downstream, the spillway gates on the Big Bend Dam opened for the first time since that dam was completed in 1964. This week, the Army Corps of Engineers increased water flowing through all six dams to more than double the previous highs set during the floods of 1975 and 1997. The flow rates are now a massive 150,000 cubic feet per second, 1.5 times greater than the typical flow of Niagara Falls. These extreme flow rates will need to be maintained into at least mid-August, and are expected to severely strain levees on the Missouri River as it flows through North Dakota, South Dakota, Nebraska, Iowa, Missouri, and Kansas. According to a press conference put on by NWS and the Army Corps last week, the Missouri River flood control system is based on an 1881 estimate of the maximum amount of water an extreme flood season could generate--40 million acre-feet of water during the spring and summer flood season. However, this year's flood is expected to pump 42 - 43 million acre feet of water into the system, stressing it beyond its designed limits. In May alone, the Missouri River basin just upstream from Sioux City, Iowa, received 10.2 million acre feet of water, more than 25% above the previous May record of 7.2 million acre feet set in 1995. Additional levee failures along the Missouri are likely this summer, particularly if widespread heavy summer rains occur.

http://www.wunderground.com/blog/JeffMasters/comment.html?entrynum=1826