Prediction of Downstream Water Quality Impacts of Devils Lake Pumped Outflows Using HEC-5Q

Since 1992 Devils Lake, a terminal lake in North Dakota, has risen nearly 7.6 meters (25 feet), flooding an additional 362 square kilometers (sq. km.) (140 square miles (sq. mi.)). In July 1999, the lake reached a peak elevation of 441.11 meters (1447.2 feet) above mean sea level, with a corresponding surface area of 518 sq. km. (200 sq. mi.). Like the Great Salt Lake in Utah, Devils Lake is highly saline due to the long-term accumulation of salts from evaporation. To alleviate flood impacts on surrounding communities, the St. Paul District, U.S. Army Corps of Engineers is investigating the feasibility and environmental impacts of pumping saline water from the lake into the fresher Sheyenne River water. The Sheyenne River flows through Lake Ashtabula, a Corps of Engineers reservoir, and into the Red River of the North, which then flows north to Lake Winnipeg in Canada, thereby creating interstate and international concerns. The Hydrologic Engineering Center's HEC-5Q program is used to address downstream water quality impacts. By simulating with- and without-pumping scenarios on the Sheyenne and Red Rivers, a quantitative evaluation of the effects can be made, including alternative operating plans for the outlet and operation of Lake Ashtabula. Vast amounts of data are conveniently handled by the HEC's Data Storage System (HECDSS). HECDSS is used to preprocess the data for input to HEC-5Q and to post-process the data from HEC-5Q for analysis.