Integrated watershed and erosion modelling for conservation prioritisation in the Kreo Sub-Watershed

Abstract

Rapid peri-urban land-use change can intensify runoff generation, strengthen sediment connectivity, and accelerate erosion and sediment delivery, thereby threatening watershed sustainability. This study integrated the soil and water assessment tool (SWAT) and the geospatial interface for the Water Erosion Prediction Project (GeoWEPP) to quantify spatiotemporal patterns of erosion and sediment transport in the Kreo Sub-Watershed (50.6 km²), Indonesia, under 2019 and 2024 land-use conditions. SWAT was calibrated and validated against observed discharge to establish hydrological reliability prior to sediment simulation, whereas GeoWEPP was used to provide physically based, hillslope-scale diagnostics under harmonised spatial and climatic inputs. Both models indicated substantial intensification by 2024. SWAT-estimated erosion increased from approximately 64,900 to 242,200 Mg∙ha⁻¹∙y⁻¹ and sediment yield from 254,700 to 406,900 m³∙y⁻¹, whereas GeoWEPP estimated an increase in erosion from 98,600 to 162,900 Mg∙ha⁻¹∙y⁻¹ and sediment yield from 216,000 to 361,500 m³∙y⁻¹. Independent verification using the volume error (VE) metric showed closer agreement for SWAT (VE = 9.1%, good) than for GeoWEPP (VE = 12.4%, acceptable), supporting SWAT as the more suitable outlet-referenced model for sediment assessment while retaining GeoWEPP for hotspot identification. These results provide a basis for conservation prioritisation based on erosion hotspots, particularly where intensified erosion sources coincide with efficient sediment-transfer pathways. Overall, the integrated and verification-constrained framework provides a robust basis for targeted sediment mitigation in rapidly changing watersheds.