Changes in the Neutralizing Distance of Thermal Pollution Caused by Thermal Power Plants in Warmer Climate Scenarios

Thermal power plants (TPPs) heat freshwater bodies by their thermal emissions that impact the biogeochemical processes and aquatic life therein. Nevertheless, as the colder water accumulates downstream (from unaffected streams), the water temperature rise due to TPPs dilutes in rivers. The impact of climate change on thermal power plants has been examined: with the increase in global water temperature, the cooling water demand increases, which increases the thermal effluent discharge whilst declining cooling efficiency. However, there is no study on the global scale that assess the impacts of TPPs in their downstream for future climate projections. In this study, we developed a flood inundation-water temperature-thermal power plant coupled model using open-sourced TPP data to simulate the thermal pollution by TTPs. We quantified the changes in the distance needed to neutralize the effects of thermal effluent discharge by TPPs (neutralizing distance: downstream distance needed to decline temperature rise below 0.1°C) under multiple climate scenarios under ISIMIP3b at a daily scale. We found that the neutralizing distance can both increase and decline in the future in response to the changes in cooling water sufficiency, despite the increase in inflow water temperature. However, in case of a series proximate TPPs in the downstream, like in Mississippi, compounding of thermal emissions increase the neutralizing distance. We also proposed adaptation measures for combating thermal pollution in a warmer climate and quantified their impacts on the neutralizing distance. We concluded that the changes in magnitude and frequency of precipitation/runoff influence thermal pollution caused by TPPs. However, adaptive measures can decline the thermal pollution per unit power production in the future upto 15% globally.