Application of a geographical information system (GIS) based hydrological model for flow prediction in Gorganrood river basin, Iran

In this paper a spatially distributed hydrologic model (WetSpa) is used to estimate daily river water discharge in Gorganrood river basin, Iran. The model combines topography, land use and soil maps, and observed daily meteorological time series to predict discharge hydrographs and the spatial distribution of hydrological parameters in the catchment. WetSpa model uses a modified rational method to calculate runoff and degree-day coefficient method to estimate the snow melt runoff based on temperature data. The runoff is routed through the basin along flow paths using a diffusive wave transfer method that enables to calculate response functions between any start and end point, depending upon slope, flow velocity and dissipation characteristic along the flow lines. The digital maps of topography, land use and soil type are 3 base maps used in the model in geographical information system (GIS) form using 90 × 90 m cell size. Results of the simulations show a good agreement between calculated and measured hydrographs at the outlet of the basin. The model predicts the daily hydrographs with a good accuracy, between 71 to 76% according to the Nash-Sutcliff criteria.   Key words: WetSpa model, distributed model, geographical information system, flow prediction.