Recent droughts and heat waves have revealed the vulnerability of some power plants to effects from higher temperature intake water for cooling. To avoid heating the cooling water beyond temperature thresholds set by the EPA, some plants have been forced to reduce their power generation. At the same time, future warming of water resources from heat waves, droughts, or climate change might increase ambient air temperature (one of the primary factors affecting intake temperature, and thus cooling effluent temperature) putting plants at risk of even greater de-rating. In this evaluation, we sought to model and predict which plants would have the greatest risk of de-rating due to thermal discharge limits. To do so, we created a regression model of average monthly intake temperatures for open loop and recirculating cooling pond systems for power plants in the Upper Mississippi River Basin using ambient air temperature, wind speed, historical intake temperatures, and historical effluent temperatures. We then integrate that information into a thermodynamic model of energy flows within each power plant to determine the change in cooling water temperature that occurs at each plant. We use these models in tandem to determine effluent temperature at 43 power plants in the Upper Mississippi River Basin. For the years modeled, 2010–2012, the model estimated the intake temperature using the linear regression within 2.2 °C of the observed values and estimated the effluent temperature within 5.0 °C of the observed values. For years outside of the estimation period, 2008–2009, the model estimated effluent temperature within 5.1 °C of the observed values.

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