Satellite-derived digital elevation model accuracy: hydrological modellingrequirements

Hydrological models can benefit from satellite-derived digital elevation mo dels (DEMs) only after determining the hydrological model sensitivity to DE M inaccuracies. This study examined how vertical errors within a SPOT satel lite-derived DEM of the 532 km(2) Little Washita River, OK, watershed affec ted hydrological predictions in the TOPLATS (topographically based land-atm osphere transfer scheme) water and energy balance model. Model predictions based on SPOT-derived DEM inputs were compared with US Geological Survey (U SGS) 7.5-minute level 1 and level 2 DEM-based predictions to determine mode l sensitivity. Ten-year simulation runs using a statistical formulation of TOPLATS indicated that while DEM inaccuracies had little effect on basin av erage output, they had a significant effect on the upper and lower quartile s of predicted water table depth. In 12-day simulation runs using a spatial ly 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 sc ales of 0.25 km(2), however, reduced differences between model-predicted va dose zone hydrology. Agreement between model-predicted water table hydrolog y was achieved at much larger scales of 5 km(2), indicating that topography and its associated error structure may have a greater influence on saturat ed rather than unsaturated hydrological modelling. Copyright (C) 2000 John Wiley & Sons, Ltd.