Assessing Water Quality And Sustainability Of Alternative Surface Water Sources In An Urbanizing Indonesian Region

Abstract

Sustainable urban water management is increasingly challenged by rapid population growth, surface water degradation, and climate variability. This study provides an integrated assessment of surface water systems to evaluate their potential as sustainable urban water sources. Focusing on four primary rivers in Malang—Metro, Amprong, Brantas, and Bango—the research incorporates hydrological analysis and comprehensive water quality evaluations, using parameters such as Biochemical Oxygen Demand (BOD), Chemical Oxygen Demand (COD), Dissolved Oxygen (DO), and turbidity. Pollution classification was performed using the Pollution Index (PI) and Storet Index, while Environmental Carrying Capacity (DDL) was used to assess future water sufficiency across districts. Results indicate that Amprong river has the highest annual water availability (17.9 million m³/year), whereas Metro river exhibits the best quality, with minimal treatment requirements. Bango river demonstrated severe pollution levels, rendering it suitable only for non-potable or backup uses. Spatial analysis revealed a mismatch between supply capacity and high-demand urban zones, indicating the need for strategic redistribution infrastructure. Additionally, climate projections suggest that by 2030, all districts will face heightened vulnerability to water stress. The findings offer a spatially explicit decision framework that integrates environmental quality, hydrological availability, and treatment needs for optimizing urban water supply. This research contributes to the advancement of ecological engineering strategies and supports policy development for climate-resilient and sustainable water management in rapidly urbanizing regions.