Mass balance analysis and calculation of wind effects on heat fluxes and water temperature in a large lake

Modeling applications often ignore the water mass balance for hydrodynamic simulations in large lakes such as the Great Lakes. However, evaluation of the water budget can be of interest, especially when water surface calculations are important, and also as it relates to the heat budget. In this study Lake Ontario is modeled using the Environmental Fluid Dynamics Code for the heating seasons in 2008–2013, with calibration focused on 2008, for which more data are available. The model is used to test both water mass and heat budgets, and various interpolation schemes for meteorological data are tested to determine the degree of sensitivity of results to the interpolation method used. The water budget incorporates flow from major tributaries and precipitation/evaporation, and it is shown that these processes alone cannot provide a balance. Missing water quantities include direct runoff and flows from smaller, probably ungauged tributaries. In 2008 the calculated quantity is 1.61 × 10¹⁰ m³ during April to September, which is equivalent to a change in water surface level of 0.7 m and represents an average flow rate of 1018 m³/s, which is larger than the inflow of any tributary to the lake except the Niagara River. Latent and sensible heat flux calculations are highly affected by wind, and interpolation of wind data is found to impact model calculations of those quantities, though different interpolation schemes do not have a strong effect on surface water temperatures. In general, the natural neighbor interpolation method is preferred over inverse distance methods.