SWAT model application to estimate streamflow in Attanagalu oya basin for sustainable water resource management

Abstract

Water crisis is prevailing as a result of the ever increasing population across the globe with advances in society and economy which significantly affects the ecosystems, environment and economy. Water resources are limited and needs to be efficiently managed by estimating streamflow. The Soil and Water Assessment Tool (SWAT) model is a physically based, continuous, computationally efficient, and distributed model considering similar slope, landuse and soil conditions as its smallest unit in the basin. It has been effectively applied at a wide range of watershed scales under different circumstances around the globe to estimate streamflow. Therefore, a process-based distributed model has to be defined and evaluated to estimate the streamflow in order to meet water demands for efficient watershed management.The objective is to evaluate the potential of process based distributed SWAT model for the estimation of streamflow in Attanagalu Oya Basin for sustainable water resource management. In this study, the SWAT model has been applied over Dunamale watershed in Attanagalu Oya basin for a period of 10 years from 2008 to 2018 on a daily time scale basis. SWAT-CUP was used as calibration and validation tool with SUFI-2 as the optimization algorithm. The model was semi auto calibrated from 2008 to 2012 and validated from 2013 to 2018. Nine parameters were selected from literature review for calibration and validation. The calibrated and validated results are plotted in flow duration curve. A total of 34 iterations were carried out with each iteration having a total simulation of 200 numbers. The process based distributed SWAT model can be developed for Attanagalu Oya Basin in Dunamale watershed to estimate streamflow with R2 value of 0.77 during calibration and 0.58 during validation with hydrograph matching pattern. The model gives a better matching for medium flow when compared to high flow and low flow and hence it can be used for sustainable water resource management. Daily model results when accumulated into monthly time frame has higher accuracy in the outcome when compared to daily and can be used in efficient decision making for water planning and management. SWAT model has more parameters and is complex when applied but the results are generated in a detailed manner with HRU as its basic unit and can be used for a better understanding of the watershed.