138-Seasonal Climate Variations and Watershed Hydrology and Water QualityResponse .

Abstract

Water is the most valuable natural resource to maintain ecological balance and sustain life on earth. In recent years, especially in the post technological revolution era, climate is being alleged to have changed, with particular reference to the increase in temperature and variations in the occurrence and distribution of rainfall. The situation is more egregious in tropical and subtropical regions where high intensity monsoon rains and changing land cover conditions have more pronounced effects on hydrologic processes. In the present study, we assessed the watershed response and variations in nutrient losses (N and P loads) from a watershed due to the changes in intra-seasonal rainfall pattern with the help of a hydrologic-water quality model: Soil and Water Assessment Tool (SWAT). We analyzed the intra-seasonal variations in the rainfall occurrence and modeled its affect on water soluble NO3—N, NH4—N, P, organic N and organic P loads moving with runoff and percolated water as pollutants of water downstream. The results of the study reveal that the NPS pollutant load in runoff varies with seasonal rainfall patterns and account for a maximum of 4.52 kg/ha as NO3—N in surface runoff from the watershed. The total loss of N from the watershed accounts for as high as 8.84 kg/ha, whereas P load is 0.02 kg/ha. These losses can be as high as 14984.14 kg of total N and 50.85 kg of total P when estimated as NPS pollutants from the watershed. The study can be useful to estimate the extent of these pollutants varying with seasonal rainfall patterns and help in managing the resources as well reducing pollution of water resources.