A semi-distributed, physics-based hydrologic model using remotely sensed and Digital Terrain Elevation Data for semi-arid catchments

Abstract

A practical, hydrologic model (DPHM-RS) is developed for the semi-arid climate of the Canadian Prairies that could adequately account for a river basin's terrain features by sub-dividing it to sub-basins of uneven shapes and sizes (semi-distributed) based on topographic information derived from the digital terrain elevation (DTED) data. Even though computationally modest, DPHM-RS is scientifically vigorous, can effectively assimilate remotely sensed (RS) data, and has most of its parameters determined through RS data and measurements. The hydrologic processes are estimated for each land cover and then aggregated according to percentage of each land cover present within each sub-basin. As evapotranspiration (ET) usually dominates the hydrology of the Canadian Prairies, ET from each land cover is estimated at three levels by the two-source model that separately considers evaporation from soil and plants. The soil moisture at the top active and the transmission zones are estimated by a water budget approach, while the groundwater dynamics by the topographic soil index obtained from DTED. The surface runoff from each sub-basin is routed to the channel network by a kinematic wave response function, and then routed to the basin outlet by the Muskingum-Cunge model. DPHM-RS, is applied to the Paddle River Basin (265 km2) of Central Alberta divided to five sub-basins. It was calibrated with hourly hydroclimatic and RS data collected in the summer of 1996 and validated with data of 1997 and 1998. In both stages, there are good agreements between simulated runoff at the basin outlet with the observed, between simulated surface temperature and net radiation with the observed, between soil moisture and that retrieved from Radarsat-SAR data, and between simulated ET and that estimated by water balance. Encouraging results from these multi-criteria assessments demonstrate the feasibility of semi-distributed, physics-based hydrologic modelling in the dry climate of Canadian Prairies, and the usefulness of RS and DTED data in basin hydrology.