Pemodelan Spasial-Temporal Kualitas Air Berbasis Spatial Stream Network untuk Mendukung Pengelolaan Berkelanjutan Daerah Aliran Sungai Beriklim Tropis

Abstract

Daerah Aliran Sungai (DAS) Cidanau merupakan sumber utama air baku bagi kebutuhan domestik, pertanian, dan industri di Provinsi Banten. Perubahan penggunaan lahan dan meningkatnya aktivitas antropogenik telah menurunkan kualitas air melalui pencemaran mikrobiologis, pengayaan nutrien, dan eutrofikasi. Penelitian ini bertujuan mengevaluasi kualitas air berdasarkan baku mutu dan indeks kualitas air, mengidentifikasi faktor-faktor yang memengaruhi variasinya, serta memodelkan distribusi spasial-temporal kualitas air menggunakan Spatial Stream Network (SSN). Penelitian memanfaatkan data pemantauan tahun 2017–2024 dan pengukuran lapangan pada sembilan stasiun selama Juni, September, dan November 2025. Analisis dilakukan menggunakan Indeks Pencemaran (IP), Indonesia Water Quality Index (IDN WQI), National Sanitation Foundation Water Quality Index (NSF WQI), analisis korelasi, Principal Component Analysis (PCA), dan pemodelan SSN. Hasil menunjukkan bahwa kualitas air periode 2017–2024 didominasi kategori tercemar ringan berdasarkan IP serta kategori sedang berdasarkan IDN WQI dan NSF WQI. Pada tahun 2025, nilai IP berkisar 0,58 – 2,99, IDN WQI 50,00 – 63,33, dan NSF WQI 46,11 – 87,21. Konsentrasi fecal coliform mencapai 20.000 MPN/100 mL dan total fosfor 0,11 – 1,26 mg/L menunjukkan bahwa kontaminasi mikrobiologis dan pengayaan nutrien menjadi tekanan utama kualitas air. Analisis korelasi menunjukkan hubungan sangat kuat antara BOD, COD, dan fecal coliform (r = 0,91 – 0,97), sedangkan PCA mengidentifikasi pengayaan nutrien, transport sedimen, dan akumulasi bahan organik sebagai faktor dominan yang menjelaskan 60,6% variasi kualitas air. Model SSN M8 memberikan performa terbaik untuk sebagian besar parameter dengan kemampuan prediksi tertinggi pada COD (R² = 0,85) dan BOD (R² = 0,77). Integrasi indeks kualitas air dan SSN memberikan dasar ilmiah bagi pengelolaan DAS Cidanau secara berkelanjutan.

The Cidanau Watershed (DAS) is the primary source of raw water for domestic, agricultural, and industrial purposes in Banten Province. Changes in land use and increased anthropogenic activities have led to water quality degradation through microbiological contamination, nutrient enrichment, and eutrophication. This study aimed to assess water quality based on established standards and indices, identify factors influencing its variation, and model the spatiotemporal distribution of water quality using a Spatial Stream Network (SSN). This study employed monitoring data from 2017 to 2024 and field measurements at nine stations in June, September, and November 2025. Analyses were conducted using the Pollution Index (IP), Indonesia Water Quality Index (IDN WQI), National Sanitation Foundation Water Quality Index (NSF WQI), correlation analysis, Principal Component Analysis (PCA), and SSN modeling. The results indicate that from 2017 to 2024, the water quality was predominantly classified as slightly polluted according to the IP, and moderate according to the IDN WQI and NSF WQI. In 2025, the IP values ranged from 0.58 to 2.99, IDN WQI from 50.00 to 63.33, and NSF WQI from 46.11 to 87.21. Fecal coliform concentrations reached 20,000 MPN/100 mL, and total phosphorus ranged from 0.11 to 1.26 mg/L, highlighting microbiological contamination and nutrient enrichment as the primary pressures on water quality. Correlation analysis revealed a very strong relationship between BOD, COD, and fecal coliform (r = 0.91–0.97), while PCA identified nutrient enrichment, sediment transport, and organic matter accumulation as the dominant factors explaining 60.6% of the water quality variation. The SSN M8 model demonstrated the best performance for most parameters, with the highest predictive ability for COD (R² = 0.85) and BOD (R² = 0.77) values. The integration of water quality indices and SSN provides a scientific basis for sustainable management of the Cidanau Watershed.