Assessment of water balance for a forest dominated coastal river basin in India using a semi distributed hydrological model

Abstract

Nagavali River plays a major role in supporting agriculture and water supply demands in parts of the Kalahandi, Rayagada and Koraput districts of Odisha and Vizianagaram and Srikakulam districts of Andhra Pradesh. With the increase in demand for water and stress from the climate change, there is a need to understand the water balance of the river basin and suggest suitable measures to improve water resources development and water harvesting. In this study, a semi-distributed model, soil and water assessment tool (SWAT) is used to study the spatio-temporal water balance for the entire basin. The model was calibrated and validated at monthly scale using the observed river discharge at Srikakulam over a period of 15 years from 1985 to 2000. Calibration and Validation results for stream flow are satisfactory on a monthly scale. The seasonal water budget analysis reveals that 70% of the annual rainfall and 74% of the annual runoff occur during the monsoon season. The sensitivity analysis showed that the lateral flow travel time, average slope steepness, curve number, available water capacity of the soil basin are the most sensitive parameters. Further the spatial analysis of the water balance components show that there is considerable difference in the precipitation and streamflow within the basin ranging from 914 to 1319 and 82 to 246 mm respectively. The results from the study provide valuable information for the proposed interlinking projects in the future.