Techno-spatial evaluation of the sustainable thermal potential and water withdrawal rates of waterbodies

The rising need for renewable energy intensifies interest in the thermal utilisation of waterbodies, which in turn gives rise to ecological risks such as thermal pollution and water quality deterioration, underscoring the need for valid potential evaluation to ensure sustainable use. Conventional evaluation methodologies often apply uniform limits for allowed water temperature changes, overlooking the diversity of waterbody typologies and existing aquatic biota, which leads to uncertainty in the sustainably usable thermal potential and water withdrawal rates. Addressing this gap, this study applies a novel techno-spatial approach, characterising waterbodies by temperature tolerance and evaluating their thermal potential considering the ecological status and technical sensitivity, in compliance with the European Water Framework Directive (WFD) and the German Surface Waters Ordinance (OGewV). Findings reveal substantial regional variation, with only 6 % of rivers displaying high tolerance to temperature change, predominantly in lowland areas. When comparing plant siting strategies, broad inclusion of all river types increases the number of possible sites and improves urban accessibility, but overall reduces available capacity due to stricter ecological thresholds. Sensitivity analyses identify water withdrawal rates and operational parameters as primary sources of technical uncertainty. These findings highlight considerable spatial, technical, and ecological constraints, and inform region-specific water-energy management. • Heat exchanger dimensioning at ≥ 4 K avoids disproportionate high flow inefficiencies. • Intake positioning of ≤ 30 km significantly boosts exploitable potential. • Potentially covering heat demand by limiting thermal plume dispersion to ≤ 20 km. • Over 50 % of potential in moderate ecological waters, one class shy of EU target. • Increased temperature tolerance follows higher flow rates, lower ecological status.