Original paper

Variations in the Stratification Regime of Onondaga Lake: Patterns, Modeling, and Implications

O'Donnell, Susan M.; O'Donnell, David M.; Owens, Emmet M.; Effler, Steven W.; Prestigiacomo, Anthony; Baker, Daniele M.

Abstract

Substantial year-to-year variations in the stratification regime of lakes, and coupled features of water quality, can occur in response to natural variations in meteorologic and hydrologic drivers. Variations in the stratification regime of hyposaline Onondaga Lake, NY, are documented for a 19 year period. The lake failed to turnover in spring of two of these years because of combined effects of saline inputs, extended ice cover and subsequent high runoff. A dynamic mechanistic one-dimensional stratification/transport and mass balance model was set-up and validated for the lake for the observed patterns of thermal stratification and salinity (S). The model performed well in matching these features, including the effects of a saline plunging tributary. The annual root mean square error (RMSE) for predictions of temperature (T) ranged from 0.8 to 1.6 °C; the overall average was 1.1 °C. The normalized (by the annual average S) RMSE for S ranged from 5 to 20%, with an overall average of 9%. Metalimnetic S maxima associated with the plunging tributary were also well predicted. The validated model, with simple oxygen depletion kinetics added, was applied to demonstrate the substantial effects natural interannual variations in the stratification regime have on the timing of the onset of hypolimnetic anoxia and its duration.

Keywords

density stratificationtransportmodelplunging inflowsalinitymodel validationhypolimnetic oxygen