Study on Pollutant Load Management in Situ Pengarengan Using SWAT Model Approach

Abstract

Modeling is an important approach for understanding complex aquatic systems, particularly in assessing pollutant loads and their effects on water quality. This study aimed to assess pollutant-load distribution and nutrient-related water quality conditions in Situ Pengarengan, Depok, West Java. Modeling was performed using SWAT+ (Soil and Water Assessment Tool Plus), a physically based hydrological model selected because it integrates topographic, land use, soil, and climate data to simulate watershed hydrology and nutrient transport. Secondary data included a Digital Elevation Model (DEM), land use and soil maps, climate data, and laboratory-based water quality data from eight sampling points. The model simulated stream discharge and channel-level nutrient outputs for 2015–2025, while field measurements were obtained from a single sampling campaign on 12 August 2025. The results indicate that pollutant transport in the catchment was mainly associated with runoff from residential and built-up areas and tended to increase during higher-rainfall conditions. In 2025, the simulated Total Nitrogen (TN) and Total Phosphorus (TP) concentrations were 41.183 mg/L and 8.79 mg/L, respectively, whereas measured TN and TP ranged from 1.61 to 3.15 mg/L and 0.23 to 0.44 mg/L. Because complete observed stream-discharge data and long-term water-quality time-series data were unavailable, the comparison was limited to preliminary verification rather than full calibration and validation. Nevertheless, SWAT+ was useful for describing hydrological response and nutrient transport patterns in the catchment.