2025-07-27 HYDROLOGICAL SCIENCES JOURNAL 2025 70(卷), 10(期), (1724-1743页)
Estimating small reservoirs' storage capacities often relies on digital elevation models (DEMs), which typically exclude underwater topography. This study proposes the UNderWater storage Reservoir inference APproach (UNWRAP), which uses existing DEM data to infer reservoirs' underwater topography based on above-water terrain features. It fits a regular geometric solid to the above-water topography and estimates its underwater portion. UNWRAP's performance was tested in Brazil's semi-arid region, using a 10 m DEM as input data and 37 746 scenarios of potential future reservoir locations and possible underwater depths at the time of DEM data acquisition. UNWRAP achieved errors between -7% and 10% relative to the reference values - smaller than those of the mean Molle's coefficient method (-14% to 382%) and the direct DEM-based approach (-83% to 0%). Although errors increased with greater underwater depths, UNWRAP provided reasonable estimates across all tested depths, showing practical and valuable information for hydrological modelling and water resources management.