Physical and Chemical Limnology of three Lakes within Hoosier National Forest
Keywords: lake morphometrics, bathymetry, water quality, Morphoedaphic index, Carlson trophic index
AbstractThree reservoirs, Tipsaw, Indian, and Celina lakes, are located in Hoosier National Forest in Perry County, Indiana, have experienced annual fish kills for over a decade. These lakes were evaluated for patterns in their physical and chemical limnology to characterize morphometrics of length, depth, and width and water quality. Chemical variables, including pH, conductivity, major ions, and nutrients, were measured to evaluate water quality differences among lakes. The study lakes were shallow depressions (Zmean 5 3.06–5.60 m; Zmax 5 7.9–17.0 m) and classified as polymictic. The shallow depths typically enabled dissolved oxygen to be distributed throughout the water column and prevented thermal stratification, although pronounced thermoclines developed during 1989, 1991, and 2001. The Carlson trophic index classified these lakes as mesotrophic with the highest index being calculated for Tipsaw (22– 52 TI), followed by Indian (12–13 TI), and Celina (5–14 TI). The highest morphoedaphic index (MEI) was observed in Tipsaw (24.3 (mg/L)/ m), followed by Indian (16.8 (mg/L)/m), and Celina (9.1 (mg/L)/m). The MEI values observed in the three lakes translate to catch yields of 20–30 kg/ha. General chemical patterns are towards a stable state or reduction in nitrogen or phosphorus concentrations. No statistically significant trend based on regression of chemical variable by lake over time was observed for any parameter during the study period (ANOVA, P .0.05). The shallow reservoir depths, changing thermocline and oxycline, and reduction in dissolved oxygen can result in increased potential for continuing conditions promoting fish kills.