Lake Water Quality Modeling for Projected Future Climate Scenarios

Abstract

AbstractA deterministic, one‐dimensional numerical simulation model for water temperature and dissolved oxygen (DO) in lakes of different size, depth, and trophic status has been formulated, validated, and applied to lakes in the north central USA. The standard error of predictions is on the order of 1 °C for temperature and 1.5 mg L−1 for DO. The model is driven by weather measurements at off‐lake weather stations. Simulations can be made for the open water season at daily timesteps and for as many years as weather data are available without any parameter adjustments. The model has been used to simulate the effect of climate change due to a doubling of atmospheric CO2 on water temperatures and DO in 27 lake classes in Minnesota. The lakes have been differentiated by surface area, maximum depth, and trophic status. Maximum water temperature near the surface is projected to increase by no more than 2 °C in midsummer, and DO will drop by less than 2 mg L−1 in the surface waters but will remain above 7 mg L−1. In contrast, hypolimnetic water temperature in mid‐summer may rise by as much as 4 °C or may become colder by as much as 4 °C. Hypolimnetic DO will be lower by as much as 8 mg L−1 in midsummer and DO depletion is projected to occur for a longer period of time in midsummer in lakes with seasonal summer stratification. Changes will be largest in spring and fall because the summer stratification season will lengthen by 20 to 90 d for different lake types.