Hydrologic assessment of a small watershed to combat agricultural drought

Abstract

Water is the most indispensable natural resources for the survival of all living beings. On the other hand, water availability is declining and the demand is increasing, making the gap between these two wider day by day.Scientific water management is a must to sustain the domestic and irrigation water needs. Quantifying the elements of hydrologic processes at micro watershed scale and at weekly or monthly temporal scale is the most important prerequisite for water resources development of a locality. For understanding the watershed characteristics and behavior, models play an important role which are also useful for extrapolating the current conditions to potential future conditions. Hydrological modeling is considered as a powerful technique in planning water resources. In this study, the hydrology of Valanchery watershed, a small sub watershed of Bharathapuzha, was modeled using SWAT, a physically based distributed watershed model. The study aims to calibrate the model, simulate the hydrologic elements and stream flow and to suggest remedies to combat the water scarcity in the study area. Using ArcGIS 10.2.2, the datasets required for the ArcSWAT was prepared. As the watershed selected for the study was ungauged, the model was calibrated for Kunthipuzha basin which lies in the immediate neighbourhood and having similar characteristics with the study area. For this, the model was initially set up and ran for Kunthipuzha basin and using the daily observed stream flow at Pulamanthole gauging station, the model was calibrated and validated. The calibration and validation periods were respectively, 2000 to 2006 and 2007 to 2009. An NSE = 0.81 and R2 = 0.82 was obtained for calibration, an NSE = 0.73 and R2 = 0.88 was received for validation. With these calibrated parameters, the model was set up and ran for the Valanchery watershed using regionalization technique. The whole watershed characteristics and behavior and that of sub watersheds and of different reaches of the mainstream were determined and predicted. It was found that the characteristics and hydrologic process elements such as surface runoff, lateral flow, deep percolation, base flow and ET of the various sub watersheds were varying considerably. Using these vital information, water resources conservation and utilization can be planned scientifically at micro spatial levels to mitigate the water scarcity scenario.