Located in the Devils Lake Basin, North Dakota, receives and stores runoff from the northern section of the basin and recharges Devils Lake. Hydrologic and water- quality conditions can vary greatly in the basin, resulting in potential economic damage. This report describes the seasonal and spatial variations in surface-water quality in the chain of lakes and its tributaries.
Long-term trends in dissolved-solids and nutrient concentrations and instantaneous loads in tributaries upstream and downstream of the chain of lakes are not apparent. However,seasonal variations are apparent. Dissolved-solids concentrations were smaller, and nutrient concentrations were larger, during the spring than during the remainder of the year. Variations in dissolved-solids concentrations are caused by dilution and evaporation. Variations in nutrient concentrations are the result of biologic activity. Instantaneous dissolved-solids and nutrient loads were greater during the spring than during the remainder of the year because of seasonal differences in flow rates.
Only minimal long-term trends and seasonal variations in dissolved-solids and nutrient concentrations in the chain of lakes are apparent. During the period of record, dissolved-solids concentrations in Sweetwater Lake generally increased, dissolved-solids concentrations in Lake Alice and Lake Irvine varied seasonally, and dissolved phosphorus concentrations in Lake Alice generally increased.
Spatial variations in dissolved-solids and nutrient concentrations in the basin are apparent." The medians and ranges of dissolved-solids concentrations for the upstream stations were smaller than those for the lake stations and the downstream stations. Dissolved-solids concentrations were larger in Channel A than in Big Coulee, and nutrient concentrations were larger in Big Coulee than in Channel A.
