ESTIMATION OF WATER TEMPERATURE EXCEEDANCE PROBABILITIES USING THERMO-HYDRODYNAMIC MODELING

A continuous simulation approach is proposed for estimating water temp erature exceedance probabilities using thermohydrodynamic modeling. Th e approach uses (1) a deterministic unsteady flow and heat transport m odel, (2) continuous hydrological and meteorological data for a long h istorical period, and (3) synthetic records of tributary water tempera tures and other model inputs. Representative historical records of str eamflow, air temperatures, and other hydrometeorological variables are obtained from nearby gages. Stochastic modeling methods are used to c onstruct synthetic records for other model inputs, including inflow wa ter temperatures. An application of this deterministic-stochastic appr oach is presented for a complex waterway in northeastern Illinois with heat discharges from several power plants and wastewater treatment pl ants. Statistical results from the continuous simulations are compared to results obtained from traditional event simulations. The applicati on illustrates the information that engineers and biologists can obtai n for (1) evaluating compliance with water temperature standards, and (2) assessing the effect of water temperatures on aquatic habitat.