Distributed small-reservoir pumped-storage hydropower in Europe: a GIS screening under drawdown and karst constraints

Continental pumped-storage hydropower (PSH) atlases omit schemes built from small reservoirs, although such sites could provide distributed flexibility. We screen this resource across 37 European countries, detecting closed depressions and water bodies and pairing upper and lower reservoirs under land-use, protection and grid-distance constraints. The reproducible workflow uses open pan-European data, a hybrid terrain stack (FABDEM; national lidar in Norway and Sweden) and an explicit allowable water-level variation for lake volume. At a 5-km grid distance and 1-m drawdown, exact maximum-weight matching gives an all-size screened bound of 2.57 TWh; excluding mapped-karst footprints for purpose-built reservoirs and sites above 2500 m leaves 0.58 TWh, of which a 21 115-site portfolio capped at 100 MWh per site stores 0.40 TWh (0.24 TWh, EU-27). Replacing FABDEM by national lidar cuts Norway’s and Sweden’s screened energy with 72% each (328.7 to 92.1 and 67.3 to 18.5 GWh): usable lake volume barely moves ( − 0.4 %), but pairs containing a dry basin collapse because that basin binds. A Sobol analysis makes maximum pair distance and karst treatment the joint controls (total effects 0.49 and 0.48). This is an exploratory first screening, not deployable capacity: it ranks where national feasibility studies should look, and their constraints can only reduce it.