Simulasi Dampak Rehabilitasi Lahan terhadap Retensi Hara menggunakan Model InVEST di DAS Ciliwung Hulu

Abstract

DAS Ciliwung termasuk kedalam DAS yang diprioritaskan karena perubahan tutupan lahan yang terjadi akibat peningkatan jumlah penduduk. Perubahan tersebut berpotensi terjadinya leaching nutrient yang dapat menurunkan kualitas air. Penelitian ini bertujuan untuk menganalisis kemampuan retensi hara N dan P pada kondisi eksisting dan skenario rehabilitasi menggunakan model InVEST NDR. Data yang digunakan meliputi peta tutupan lahan, Digital Elevation Model (DEM), curah hujan rata-rata 10 tahun, tabel biofisik, dan batas DAS. Hasil penelitian menunjukkan bahwa rehabilitasi sekitar 3.167,12 ha lahan kritis menjadi hutan mampu menurunkan ekspor N dan P, dengan penurunan Nitrogen dan Fosfor mencapai sekitar 39%. Konsentrasi TN dan TP juga lebih tinggi pada musim penghujan dibandingkan musim kemarau, sejalan dengan hasil pemodelan. Rehabilitasi lahan meningkatkan retensi hara, mengurangi limpasan permukaan, dan berpotensi mendukung pengelolaan DAS Ciliwung Hulu untuk menjaga kualitas air.

Ciliwung Watershed is one of Indonesia's priority watersheds due to land cover changes driven by rapid population growth. These changes increase the potential for nutrient leaching, which may degrade water quality. This study aimed to analyze nitrogen (N) and phosphorus (P) retention under existing conditions and a land rehabilitation scenario using the Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST) Nutrient Delivery Ratio (NDR) model. The data used included land use/land cover maps, a Digital Elevation Model (DEM), 10-year average rainfall data, a biophysical table, and watershed boundary data. The results showed that rehabilitating approximately 3,167.12 ha of degraded land into forest reduced N and P exports, with nitrogen export decreasing by up to 39%. Total Nitrogen (TN) and Total Phosphorus (TP) concentrations were also higher during the rainy season than in the dry season, consistent with the model simulation results. Land rehabilitation improved nutrient retention, reduced surface runoff, and has the potential to support sustainable watershed management for maintaining water quality in the Upper Ciliwung Watershed.