A Simple Quantitative Model to Estimate Consumptive Evaporation Impacts of Discharged Cooling Water with Minimal Data Requirements

Abstract

This paper provides a early-stage analysis tool with minimal data requirements that can be used to quantify the consumptive water use from cooling operations and determine if additional data gathering or more detailed analysis is required. We develop and present a quantitative model to predict increased evaporation rates from the discharge of heated cooling water to a receiving water body. This model can be a screening tool for policy and decision makers, requiring minimal data to quickly estimate water loss from evaporation for various alternatives and impact evaluations. The model is based on standard evaporation estimation methods, modified to consider the higher atmospheric saturation gradient resulting from the heated water. The model requires minimal data; ambient air temperature, heated plume temperature, relative humidity, and wind speed. When comparing impacts from various alternatives, the change in evaporation is more important than the total evaporation and we show that the change in evaporation from the discharge of heated cooling water is independent of relative humidity, further reducing data requirements. We present graphs of model behavior over a range of expected conditions and discuss this behaviour.