Abstract

The U.S. Geological Survey, in cooperation with the Idaho Department of Water Resources, calculated annual water budgets and a mean annual water budget for Coeur d’Alene Lake, Idaho, for water years 2000 through 2005. Mean annual inflow to Coeur d’Alene Lake, including precipitation, was about 167,110 million cubic feet. Mean annual outflow, including evaporation, but excluding wastewater effluent to the Spokane River, was about 167,850 million cubic feet. The amount of water lost from Coeur d’Alene Lake and the Spokane River to the Spokane Valley-Rathdrum Prairie aquifer was estimated at 7,250 million cubic feet. Mean annual precipitation into Coeur d’Alene Lake was 3,267 million cubic feet, which exceeded mean annual evaporation of 2,483 million cubic feet. Withdrawals directly from the lake and from wells within a 1,000 foot buffer of the lakeshore for domestic and municipal water uses were reported. However, only the estimate for the consumptive use part of the withdrawals, 265 million cubic feet, was considered in the budget. Mean annual change in lake storage resulted in a net loss of about 49 million cubic feet. The mean annual residual value was about -8,310 million cubic feet.