Hydrological Condition Analysis Using the SWAT Model and Statistical Analysis Based on Streamflow and Sediment Yield in the Bajing Sub-Watershed, Jember, Indonesia

Abstract

This study aimed to assess the hydrological conditions of the Bajing Sub-watershed, Jember, Indonesia, by integrating the Soil and Water Assessment Tool (SWAT) with statistical analysis of streamflow and sediment yield to provide scientific evidence for sustainable watershed management. A quantitative approach combining GIS-based spatial analysis, SWAT hydrological modelling, and statistical analysis was applied using climate, land cover, soil, and topographic data for the 2016–2024 period. Streamflow and sediment yield were simulated at the watershed outlet and analysed using descriptive statistics, coefficient of variation (CV), trend analysis, boxplots, and linear regression to evaluate hydrological variability and the relationship between streamflow and sediment yield. The Bajing Sub-watershed was dominated by forest cover (67.90%), Andisols (54.60%), and flat to gentle slopes (51.35%), indicating generally favourable watershed conditions. Simulated streamflow ranged from 2.24 to 430.00 m³/s, with a mean of 132.93 m³/s (CV = 73.17%), while sediment yield ranged from 0 to 1.60 tons, with a mean of 0.30 tons (CV = 113.90%). A strong positive correlation was observed between streamflow and sediment yield (r = 0.90), with streamflow explaining 81% of sediment-yield variability (R² = 0.81). Despite the predominance of forest cover, high seasonal variability in streamflow indicates that intense rainfall and steep slopes may increase runoff and sediment transport during peak-flow periods. Integrating SWAT simulation with statistical analysis effectively characterised the hydrological dynamics of the Bajing Sub-watershed and identified key factors influencing streamflow and sediment transport. The findings provide a scientific basis for sustainable watershed management by emphasising the importance of maintaining forest cover, implementing soil conservation on steep slopes, and controlling land-use change to reduce erosion risk and preserve watershed hydrological functions.