The cooling demand of cities is currently increasing due to urban heat island effects which could be covered with renewable energy to reach climate goals. An efficient solution is thermal cooling using groundwater. This approach involves introducing waste heat into the aquifer, which, at the same time, also raises some concerns among water authorities about potential impacts on groundwater quality. Hence, strict regulations were imposed on temperature spreading and maximum injection temperatures, limiting the thermal use of groundwater for cooling. However, regulations vary widely by country, because the influence of such temperature changes on groundwater conditions is still uncertain. In the present study, a summary of country-specific regulations is presented and evaluated with respect to possible impacts. Based on the review, a novel approach for the comparative assessment of the influence of different legal frameworks on city-wide relevant thermal impact areas is presented and implemented in three urban case studies in Germany, Switzerland and Spain, with various hydrogeological conditions.
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