Simulation of Impact of Change in Landuse on Water Yield of Upper Manair Catchment

Land use plays an important role in controlling hydrologic response of catchment, particularly in terms of the nature and magnitude of surface water and ground water interactions and surface water availability. The change in land use controls the water yield of surface streams and groundwater aquifers and thus the amount of water available in a watershed. Hence, the hydrological model SWAT has been applied to upper Manair catchment, Andhra Pradesh, India to determine the impact of land management practices and change in land use on water yield for sustainable use. The model was run for a period of 21 years, i.e.1992 to 2012. It was calibrated against observed reservoir volumes using Nash Sutcliffe criteria (0.85). To obtain sustainability of ground water resources in the watershed, it was tried to simulate the water balance components by reducing the area under paddy cultivation through three alternate cropping scenarios. The evaluation of three scenarios clearly demonstrated the impact of conversion of paddy (water intensive crop) on the hydrology of watershed. The base flow was reduced from 31.42mm to 6.21mm. The lateral flow through soil has decreased to 3.05mm from 3.92mm. The deep aquifer recharge has been reduced to 356.79mm from 464.51mm. Actual ET has been increased to 592.8 from 545.1mm due to more vegetation. It can be concluded that converting paddy area to dry land crops will enhance availability of surface water resources and decrease ground water resources.