Analisis Perubahan Tutupan Lahan Terhadap Karakteristik Hidrologi DAS Setail Menggunakan Model SWAT+

Abstract

The Setail Watershed is one of the watersheds in Banyuwangi Regency that has experienced land cover changes, which may affect its hydrological characteristics, particularly river dischange and surface runoff. This studi aims to analyze the performance of the SWAT+ model in predicting river discharge, evaluate the calibration and validation results of the model, and identify the type of land cover that contributes most to the increase in surface runoff in the Setail Watershed. The study was conducted using the SWAT+ model with input data consisting of DEM, soil type, land cover, climate data and observed discharge data. The modelling process was carried out using QSWAT+, SWAT+ Editor and SWAT+ Toolbox, while model performance was evaluated using the coefficient of determination (R2), Nash-Sutcliffe Efficiency (NSE) and Percent Bias (PBIAS). The calibration results yielded an R2 0f 0.60, an NSE of 0.56, and a PBIAS of -0.35, whereas the validation results produced an R2 of 0.50, an NSE of 0.44, and a PBIAS of -20.58. there results indicate that the model was reasonably capable of representing the general streamflow pattern, although it tended to overestimate streamflow during validation. Built up (URBN) increased from 3.38% in 2005 to 11.04% in 2025. This expansion was accompanied by an increase in surface runoff from 833.361 mm to 962.040 mm and a decrease in percolation from 535.234 mm to 400.218 mm. therefore, the expansion of built up (URBN) areas was identified as the primary factor contributing to increased surface runoff and reduced subsurface water storage capacity in the Setail Watershed.