HYDROLOGIC BEHAVIOUR OF HIGHLAND CATCHMENT IN HUMID TROPICAL REGION USING QSWAT MODEL

Water resources planning and management of a region requires an understanding of the water balance in the region. The Soil and Water Assessment Tool (SWAT) with QGIS interface (QSWAT) has been used here to arrive at the water balance components in the Palapuzha watershed of Valapattanam river basin in Kerala. Valapattanam river drains an area of 1867 sq.km. with 456 sq.km. area in Karnataka State. The river basin receives an average annual rainfall of 3600 mm. The Palapuzha watershed drains an area of 237.25 sq.km with an average annual rainfall of 4562 mm. The QSWAT model has been calibrated and validated using data for a period of eight years (2000-2007) for which both rainfall and streamflow data are available. The model was successful in simulating monthly streamflow during the calibration and validation periods with Nash Sutcliffe efficiency and correlation co-efficient greater than 0.75 and percent bias less than 10%, showing that the model is very good for predicting streamflow in Valapattanam river basin. This calibrated model was used to arrive at the different water balance components in the Palapuzha watershed. The results obtained will be useful for the sustainable development and planning of the water resources system in the highland humid tropical watersheds.