Effect of Land Use Change on Water Balance Components of Gharib Abad Watershed, Sistan and Baluchestan Province

Aims Accurate and timely estimates of the water balance are necessary for the maintenance of surface and underground waters. The purpose of the present study was to investigate effect of land use change on the water balance of Gharib Abad Watershed using the WetSpa model. Material & Methods The present study was carried out in Gharib Abad Watershed in Zahedan with a total area of 9924.4ha in Sistan and Baluchestan Province. Firstly, the model was implemented for the statistical period of 2008-2016 using the land use map of 2016, so that to calibrate the model, the statistical period of 2008-2012 and to validate the model the statistical period of 2012-2016 were selected. Then in order to investigate the effect of the land use change on water balance, all data and maps used in the model were maintained fixed (except for the land use map) and the model was simulated using the land use map of 2000. Findings In the land use of 2000 from total precipitation, the evaporation rate was 69.60%. In addition, 4.13% of the total precipitation was stopped and evaporated by vegetation cover. Moreover, 26.27% have been converted to runoff. While in the land use of 2016 the evaporation increased by 9.01%, the vegetation cover decreased by 2.42%, the runoff decreased by 6.59%. Also, k_(g ) and k_(ep ) were identified as the most sensitive parameters. Conclusion The WetSpa mode has well estimated the components of the water balance of watershed and has the necessary efficiency in arid areas.