Assessing Water Quality and Prioritizing Pollution Control Strategies for Brangkal River, Mojokerto City, Using WQI and AHP Approaches

Abstract

The Brangkal River supports domestic, agricultural, and economic activities in Mojokerto City; however, it is increasingly subjected to anthropogenic pressures. This study aims to analyze the water quality and pollution status of the Brangkal River and to formulate water pollution control strategies using the Analytic Hierarchy Process (AHP). Water quality analysis was conducted based on laboratory measurements carried out in March and July 2025.

The results indicate that the Brangkal River is generally classified as lightly polluted, with Pollution Index values ranging from 1.62 to 3.81 during the period 2021–2024. Laboratory test results from water samples collected in July 2025 showed poorer conditions compared to those obtained in March 2025. At one monitoring point in July 2025, the river reached a moderately polluted status. Of the eight parameters analyzed, those exceeding the water quality standards included Total Suspended Solids (TSS), recorded at 76 mg/L at the upstream point and 69.1 mg/L at the midstream point; Biological Oxygen Demand (BOD), at 4.3 mg/L upstream and 3.44 mg/L midstream; Dissolved Oxygen (DO), at 5.7 mg/L upstream, 5.5 mg/L midstream, and 5.6 mg/L downstream; and fecal coliform levels at all three points (upstream, midstream, and downstream), ranging from 9,200 to 16,000 MPN/100 L. All of these parameters consistently exceeded the established standard limits.

These conditions indicate significant organic and nutrient pollution, primarily associated with untreated domestic wastewater and surface runoff. The AHP analysis of the Brangkal River restoration strategy to support sustainable management highlights the need for an integrated approach encompassing ecological, social, technical, and institutional aspects.

The resulting strategic priorities indicate that river water quality monitoring is the primary alternative for pollution control efforts, followed by improving community behavior toward the river, protecting biodiversity, increasing public participation, and strengthening environmental supervision and law enforcement.

These strategies emphasize that the success of Brangkal River restoration is highly dependent on synergy among government, communities, and relevant stakeholders in implementing integrated and sustainable river management programs.