Application of the CE-QUAL-W2 Hydrodynamic and Water Quality Model to Fort Peck Reservoir, Montana.

摘要

The District developed a CE-QUAL-W2 water quality model for Fort Peck Lake after the completion of the three-year intensive water quality survey to assess water quality conditions and coldwater habitat volume in the reservoir. The reservoir model was configured to compute temperature, dissolved oxygen, and organic nutrients using semi-deterministic algorithms, and it was calibrated to 2004 through 2006 water temperature and dissolved oxygen measurements from the intensive water quality survey period, and in 2007 and 2008. Additional simulations evaluated the effectiveness of releasing warmer water from a hypothetical high-level reservoir withdrawal to the Missouri River for pallid sturgeon habitat enhancement downstream of Fort Peck Dam. The calibrated model predicted temperature in degrees Celsius and dissolved oxygen concentrations in milligrams per liter (mg/L) in the reservoir with root mean square errors of 1.02 and 0.57, respectively. The model predicted reservoir discharge temperature and dissolved oxygen concentrations with root mean square errors of 1.01 and 1.80, respectively. Predicted discharge temperatures from the existing Fort Peck outlet peaked between 17 deg C and 18.5 deg C from 2004 through 2007, while in 2008, the year of the highest average pool elevation, predicted discharge temperature peaked near 16.5 deg C. These model results suggest low pool elevations yield warmer discharge temperatures, while high pool elevations yield cooler discharge temperatures. Ambient air temperatures also have an influence on lake water temperature and discharge temperature. During 2004, the coldest simulation year, the model predicted cooler discharge temperatures than in 2005 through 2007, the other low-pool years. No discernable impact was observed in predicted discharge DO concentrations as a result of pool elevation.