Weather-Based Variations in Thermal Stratification

A one-dimensional mixed-layer mathematical model of thermal stratification was used to evaluate the sensitivity of stratification conditions in a future reservoir to natural variations in attendant meteorological conditions. Weather data collected for 13 years at the National Weather Service (NWS) Station in Allentown, Pennsylvania, were included in the analysis. Wind speed, and the temporal variability in wind speed, were observed to be lower during summer. The simulated stratification regime was found to be extremely sensitive to meteorological conditions, as evidenced by the wide range of features of stratification that were projected for the 13 years of NWS data. The influence of the variability of wind from year to year was particularly evident in the broad ranges in the depth of the epilimnion in spring and fall, the temperature of the hypolimnion, and the duration of stratification. It is concluded that meteorological inputs need to be defined accurately for the development of credible stratification models, and that the influence of weather-based natural variability in stratification should be considered in the analysis of related environmental parameters.