Evaluating Surface Runoff Responses to Land Use Changes in a Data Scarce Basin: a Case Study in Palas Basin, Turkey

Abstract

In this study, hydrologic regimes of the Palas basin have been investigated with land use/land cover (LULC) change. To investigate the relationship between precipitation and surface runoff, a SWAT (Soil and Water Assessment Tool) model was developed and runoff response was analysed under different LULC conditions. Firstly, Post classification change detection technique was used to prepare time series LULC maps of the years 1987, 2000 and 2011. The overall classification accuracy of 86% and Kappa Coefficient (K) of 0.82 were achieved. Then model was manually calibrated using monthly historical streamflow records. The calibration was successful with coefficient of determination (R 2) value of 0.61 and the Nash and Sutcliffe efficiency value of 0.55. Validation of the calibrated model using independent dataset shows even better model performance with Nash and Sutcliffe efficiency value of 0.62 and R 2 value of 0.85. The results of this research study are as follows. Agriculture area in Palas Basin considerably expanded (47%) in the last 24 years. Consequently, the area of bare soil declined (36%) markedly during the period 1987–2011. Simulations of runoff for the 2000–2011 period with the SWAT model showed that, under the LULC conditions of 1987, surface runoff would be 40% lower compared to runoff under the LULC conditions of 2011. For the development of sustainable water resource strategies, it is essential to establish interaction between land use changes and local hydrology. Although more observed data is needed for model accuracy, SWAT can provide useful data for water sources planners and policy makers.