Satellite-derived digital elevation model accuracy: hydrological modelling requirements

Hydrological models can benefit from satellite-derived digital elevation models (DEMs) only after determining the hydrological model sensitivity to DEM inaccuracies. This study examined how vertical errors within a SPOT satellite-derived DEM of the 532 km2 Little Washita River, OK, watershed affected hydrological predictions in the TOPLATS (topographically based land–atmosphere transfer scheme) water and energy balance model. Model predictions based on SPOT-derived DEM inputs were compared with US Geological Survey (USGS) 7·5-minute level 1 and level 2 DEM-based predictions to determine model sensitivity. Ten-year simulation runs using a statistical formulation of TOPLATS indicated that while DEM inaccuracies had little effect on basin average output, they had a significant effect on the upper and lower quartiles of predicted water table depth. In 12-day simulation runs using a spatially explicit formulation of TOPLATS, which used 30-m grid cells across a 600 000 pixel model domain, elevation errors propagated into model predictions of soil moisture, runoff, evapotranspiration, incoming solar radiation and surface skin temperature. Aggregation of the 30-m pixel model output to scales of 0·25 km2, however, reduced differences between model-predicted vadose zone hydrology. Agreement between model-predicted water table hydrology was achieved at much larger scales of 5 km2, indicating that topography and its associated error structure may have a greater influence on saturated rather than unsaturated hydrological modelling. Copyright © 2000 John Wiley & Sons, Ltd.