Abstract
This research addresses the effect of using digital elevation models (DEMs) derived from different sources on the results of a kinematic wave based GIUH model. DEMs from different sources exhibit data-resolution effects on the important derived geomorphological properties of watersheds used in rainfall–runoff modelling. Using DEMs derived from topography maps (TOPO DEM) and the SRTM DEM, it was illustrated that different threshold areas for stream network extraction affect GIUH model performance. The results show that the SRTM DEM gives higher values for sub-basin and channel slope as well as number of streams, than the TOPO DEM, while mean length of overland and channel flow is greater for the latter source. The results also indicate that peak flow and slope of the hydrograph rising limb obtained from the SRTM DEM at different threshold areas (ranging from 0.25% to 3%) are greater than that for the TOPO DEM. Investigating the effects of stream network delineation threshold area on the simulated peak flow shows that the maximum and minimum differences (12% and 1%) occur at the threshold areas of 0.5% and 1%, respectively, while for threshold areas higher than 2% the difference in peak flow of the two sources is limited to 10%. Based on the results of this research, it is deduced that the effects of data resolution and stream network delineation threshold areas on the geomorphological parameter values and the performance of GIUH-based models are significant and should be considered when using SRTM DEMs in ungauged watersheds.Keywords: SRTM DEM, topographic maps, rainfall–runoff Modelling, KW-GIUH, threshold area
Highlights
One of the most important steps in hydrological modelling is the extraction of the geomorphological parameters of watersheds
The results indicated that both digital elevation models (DEMs) gave the same pattern for the stream network, but that the simulated runoff was different
The results indicated that the sub-basin area and perimeter extracted from the SRTM DEMs was more accurate than that extracted from the NAD and USGS DEMs
Summary
One of the most important steps in hydrological modelling is the extraction of the geomorphological parameters of watersheds. Due to the use of digital elevation models (DEM), this extraction is simple. Maathuis and Sijmons (2005) have indicated that the lack of adequacy, accuracy, and access to such sources is one of the most important problems faced by researchers, especially in developing countries. Satellite-based DEMs have found extensive use in hydrology and other earth sciences. These DEMs can be provided from different sources with a wide range of resolutions. With a DEM of appropriate resolution, watershed para meters can be computed with an acceptable accuracy
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