Seasonal Assessment of Water Quality and Pollution Index of Cileungsi River in Bogor Regency, Indonesia

The Cileungsi River is the upstream part of the Bekasi Watershed, and its existence is crucial for the sustainability of the local economy and the survival of the community, industry, agriculture, and commerce surrounding the riverbanks. It is also the raw water source for Regional Water Company. This study aims to assess the water quality of the Cileungsi River and its pollution status using the Pollution Index (PI) method. This research was conducted at six sampling points, covering the upstream, middle, and downstream sections in both the dry and rainy seasons of 2022. The method used to analyze the water quality of the Cileungsi River refers to the Indonesian National Standard. In contrast, the calculation of the PI refers to the Decree of the State Minister of Environment. During the dry season, the PI at the Regional Water Company bridge in Kota Wisata and beside PT Rahayu Indah Kulit fell into the moderately polluted category, with PI values of 5.49 and 7.30, respectively. The highest PI value during the rainy season was recorded at 10.30 on the border of Bogor Regency and Bekasi City, which falls within the heavily polluted category. The Gunung Putri area has a lightly polluted index value in both seasons. The parameters that require attention are BOD, NO2-, free chlorine, and fecal coliform, which serve as indicators of pollution from household and agricultural activities. These results will help the Bogor Regency government develop strategies to protect and sustainably manage the Cileungsi River.