Simulating the impact of check dams on river flow - a case study in bharathapuzha river basin

Abstract

The state of Kerala faces severe water stress during summer months. One of the most feasible solutions to this problem is the livening of the rivers of Kerala. Hence, a pilot study has been carried out on Bharathapuzha, which is the lifeline of several millions of people in the state. This study focused on implementation of check dams for improving summer flow regimes of the river. The project is aimed to improve the yield of Kunthipuzha, one of the tributaries of Bharathapuzha. It has a catchment area of 822.22 km 2 . Micro watershed delineations and their topographic analysis were carried out with the help of ILWIS and SWAT. Digital Elevation Model (DEM), drainage network, soil map and land use map for the catchment were prepared by utilizing the integrated GIS and image processing capability of ILWIS. SWAT was set up and calibrated for the basin with good simulation efficiency and the calibrated model was used to analyze the water balance of the whole basin and that of the individual subbasins. The statistical measures of NSE and COD were used to evaluate the model’s predictive capability. The model showed an NSE of 92 % and COD of 99 % for the monthly simulation in the calibration period and NSE of 47 % and COD of 97 % in the validation period. The base flow contribution showed a significant increase during summer months when a number of check dams were incorporated and this in turn resulted in considerable enhanced yield of the basin. The graphs showing the comparison of simulations without, with 24 & 50 checkdams was plotted on daily, monthly and annual basis for different years. Approximately an increase in discharge of 0.32m 3 /s during summer months was obtained when a total of 50 check dams were added. There is scope for further research to optimize the number and location of check dams. Similar studies can be extended to other river basins of Kerala.