EVALUASI PERUBAHAN TUTUPAN LAHAN TERHADAP FLUKTUASI DEBIT ALIRAN RENDAH DI DAS JUANA

Abstract

Land cover changes in the Juana Watershed continue to occur as the demand for building, residential, and industries increases. Today, Juana Watershed is experiencing a decline in water discharge due to prolonged drought, with the water level of the Silugonggo River dropping by up to 50 cm per day. Land cover changes within a watershed significantly affect hydrological balance, particularly low-flow. This research investigates the impact of land cover changes on low-flow fluctuations in Juana Watershed from 2017 to 2023. Land cover changes analysis utilizes secondary data by verifying shapefile data through digitization satellite image-based from Google Earth and classified into five categories: forest, agricultural, built area, crop land, and water bodies using ArcGIS software. The low-flow analysis uses FJ. Mock method. The evaluation of land cover changes on low-flow fluctuations is conducted by comparing the land cover changes with the maximum low-flow for each period. The results of this study indicate that land cover in Juana Watershed from 2017 to 2023 was predominantly agricultural area, 51%. During this period, 8,3% of forest was converted into built area and crop land, with 3,4% and 4,9% respectively. Where FJ. Mock model is considered reliable in predicting low-flow in Juana Watershed, with R² = 0,93 and NSE = 0,79 and the maximum low-flow values 162,50 m³/s, 146,01 m³/s, 74,93 m³/s, 107,33 m³/s, 117,96 m³/s, 139,08 m³/s, and 172,69 m³/s, respectively. The conversion of forest into built area and crop land resulted in two different conditions of maximum low-flow. From 2017 to 2019, this conversion led to a decline in maximum low-flow. This decline was accompanied by an increase in the duration of the dry season from 2017 to 2019, with 2019 recording the longest duration for 6 month 10 days. Meanwhile, from 2020 to 2023, the conversion of forested land into built area and crop land led to an increase in maximum low-flow. To mitigate this risk, land conservation efforts in the upstream area are necessary through reforestation and soil conservation techniques.