<![CDATA[The Brantas River Basin plays a strategic role in supporting domestic, agricultural, industrial, and ecological functions in East Java, Indonesia. Rapid urbanization, land-use change, and increasing anthropogenic activities have exerted significant pressure on river water quality, necessitating comprehensive and reliable assessment methods. This study aims to evaluate the water quality status of the Brantas River using the Pollution Index (PI) approach, which has been widely adopted for river quality assessment in Indonesia and other countries. Secondary water quality data were analyzed, encompassing key physical and chemical parameters, including biochemical oxygen demand, chemical oxygen demand, dissolved oxygen, total suspended solids, nutrients, and selected heavy metals. The PI values were calculated based on Indonesian water quality standards and interpreted according to established classification criteria. The results indicate that most monitoring points along the Brantas River fall into the moderately to heavily polluted categories, reflecting cumulative pollution loads from domestic wastewater, industrial discharges, and agricultural runoff. Comparative analysis with previous studies confirms the consistency of PI-based assessments and highlights spatial variability influenced by land use and human activities. This study demonstrates that the Pollution Index method is an effective and practical tool for evaluating river water quality and provides a scientific basis for pollution control strategies and sustainable river basin management in the Brantas River Basin.]]>
