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Quantifying the components of the water balance for a watershed is important towards understanding the
movement and transformation of water in a watershed or region. Land use changes in a watershed can
affect water availability by altering hydrological processes such as infiltration, groundwater recharge,
base flow and runoff. Application of watershed models provide accurate estimate of components of water
balance thereby availability of water resources. Hence, the watershed model SWAT has been applied to
quantify various components of water balance and the impact of land cover change in Upper Manair
catchment which comprises parts of the Medak, Nizamabad and Karimnagar districts of Andhra Pradesh,
India.
SWAT model was run on upper Manair catchment database for a period of 21 years (1992 to 2012). It
apportioned precipitation and irrigation of catchment into different water balance components in which
percolation has amounted to 618.72 mm followed by actual evapo-transpiration as 545.1mm and deep
aquifer recharge as 464.51 mm. Surface runoff (70.55 mm) and lateral flow (3.92 mm) contributed less.
The model was calibrated against observed reservoir volumes using Nash Sutcliffe criteria (0.85). The
water balance components of different hydrological response units were simulated which has clearly
indicated the impact of land use and soil type on the water yield of the catchment. Paddy accounted for
more runoff and cotton and maize contributed less base flow and lateral flow to stream flow.
Keywords: Water resources, Upper Manair, watershed, Modelling.