Simulation of Land use Change Scenarios (Increases in Residential Areas) Impacts on Hydrological Parameters Using WetSpa Model in the Ziarat Gorgan Watershed

Land-use changes by human activities are important issues in regional planning. The distributed hydrologic model is a suitable model to survey land-use changes and to estimate their quantities. This study aims to evaluate the effects of land-use changes (the expansion of residential areas) on the hydrological parameters using WetSpa model in the Ziarat Watershed, which has an area of 95.15 square kilometers. In order to execute the model, during the four-year period (2007-2010), the hourly hydrometeorology data including rainfall, temperature, evapotranspiration, and discharge rate are used as inputs. Additionally, three base maps of the digital elevation model (30meter cell size), soil map (soil texture), and land-use are also applied. As a result, there is a good agreement between the simulated and observed hydrographs. The scenarios of land-use changes (the expansion of residential area) have been used as input maps for the calibrated model in a GIS environment. The results show that some hydrological parameters such as the peak discharge, potential runoff coefficient and flow velocity increase in the all scenarios, but the Manning’s roughness coefficientis reduced.