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Soil, water and air are the primary requirements for the existence of life on earth. Efficient distribution and sustainable use of water resources has to be managed on watershed basis. A watershed is a geographical area which receives water through precipitation and drains out to a common outlet. Watershed scale
hydrological studies consider the weather conditions and physiographic features of the watershed as input factors. Changes in any of these parameter definitely will
influence the watershed hydrology. Climate models are the most important tool for making climate predictions on temporal and spatial scales and making projections of future climate for the
coming century. In the present study, Kurumali sub basin of Karuvannur river was
selected as the study region. Future projected climate data was obtained from MarkSim DSSAT weather file generator for the future 30 years (2020-2050) using MIROC-ESM general circulation model in four RCPs(2.6,4.5,6.0 and 8.5).Present
annual rainfall for Kurumali sub basin is 2767.3mm. The model predicted annual
rainfall for 2050 are 3179.8mm, 3387.2mm, 3397.4mm and 3344.9mm in RCP 2.6, RCP 4.5, RCP 6.0 and RCP 8.5 respectively. This data was used as weather input
for predicting the future watershed processes and water resource availability using
SWAT model. The model predicted an increase in annual rainfall and a decrease in
duration of individual storms. An increase in the amount of SW monsoon rainfall and a decrease in the amount of NE monsoon was predicted. Soil and Water Assessment Tool (SWAT) is a widely accepted model for the river flow calculation, sediment transport estimation and nutrient availability
computations. SWAT wasused for the water balance computation. Surface runoff
was found to increase from 254.9mm to 885.3mm in RCP 2.6; 852.5mm in
RCP4.5; 885.3mm in RCP 6.0 and 918.1mm in RCP 8.5. Lateral flow also showed
an increase from 288.2mm to 459.1mm RCP 2.6; 491.9 mm in RCP 4.5; 459.06mm
in RCP 6.0 and 459.06mm in RCP 8.5.The groundwater flow was found to reduce from 1622.2mm to 1310.9mm in RCP 2.6; 1532.5mm in RCP 4.5; 1574.4mm in RCP 6.0 and 1543mm in RCP 8.5. Predicted high intensity short duration rainfall will
enhancerunoff.Evaporation losses were also found to increase and this in turn will
reduce the water availability of the Kurumali sub basin.The reduced aquifer recharge consequent to high runoff and evaporation losses will disturb the demand supply balance of water within the watershed. Adoption of suitable soil and water
conservation measures are recommended to overcome the water scarcity expected in future years.