USGS Publications Warehouse

Abstract

Devils Lake is a closed-basin lake characterized by large fluctuations in water level and in concen- trations of dissolved chemical constituents. A study was conducted to assess spatial and seasonal variability in water-quality conditions in Devils Lake during September 1988 through October 1990. Specific conductance generally increased from west to east in Devils Lake and East Devils Lake. pH, water temperature, and dissolved oxygen generally were similar among sites. Devils Lake generally does not undergo thermal stratification during open-water periods but does undergo inverse thermal stratifi- cation in the winter. The potential exists for establishment of near-bottom anoxia during the summer and during the winter. Most inflow enters the western part of Devils Lake and becomes progres- sively more concentrated by evaporation as it moves eastward through Devils Lake and East Devils Lake. Concentrations of all major ions, except calcium, bicarbonate, and sulfate, were larger in water samples from Devils Lake and East Devils Lake than in water samples from tributaries. Concentrations of all major ions generally increased eastward through Devils Lake and East Devils Lake, but sodium, sulfate, and chloride were enriched relative to the other major ions. Dissolved-solids concen- trations varied both spatially and seasonally. Median dissolved-solids concentrations generally increased from west to east. Dissolved-solids concentrations generally were largest in the winter, smallest in the spring, and increased in the summer and fall. Nutrients also varied spatially and seasonally. Nutrient concentrations tended to be largest at shallower sites. The ratio of sediment surface area to lake volume for a given part of the lake may partly explain spatial variability in concentrations of nitrogen species.