Integrated River Health Assessment in the Sungai Muda Basin Using the River Health Index (RHI): Comparison between the 2023 Baseline and the 2025-2026 Assessment

Abstrak

River health assessment is essential for sustainable water resource management because river ecosystems are influenced by physicochemical, biological, physical habitat and anthropogenic factors. Conventional monitoring in Malaysia primarily relies on the Water Quality Index (WQI), which evaluates only physicochemical water quality and may not adequately represent the overall ecological condition of a river. Therefore, this study applied the River Health Index (RHI) to evaluate the health status of the Sungai Muda Basin and compare the current condition with the 2023 baseline assessment. Eight monitoring stations distributed from the upstream to downstream sections of the basin were assessed during the 2025–2026 dry season. The assessment integrated four RHI sub-indices, namely chemical, biological, physical habitat and sociological components. The chemical assessment employed the Department of Environment Water Quality Index (WQI), while biological assessment utilized the Biological Monitoring Working Party (BMWP) scoring system and Biological Water Quality Index (BWQI). Physical habitat and sociological assessments were conducted according to the Department of Irrigation and Drainage River Health Index guideline. The results demonstrated that all monitoring stations achieved Category A (Very Healthy), with the mean RHI increasing from 75.39 during the 2023 baseline assessment to 83.98 in the 2025–2026 assessment. The mean WQI also increased from 78.13 to 88.17, indicating substantial improvement in physicochemical water quality. Correlation analysis revealed a very strong positive relationship between WQI and RHI (R² = 0.9943), whereas weak relationships were observed between BWQI and RHI (R² = 0.0115) and between WQI and BWQI (R² = 0.0244). These findings indicate that biological communities respond to additional ecological factors beyond water chemistry alone. The River Health Index therefore provides a more comprehensive framework for evaluating river ecosystem health and supports sustainable river monitoring and management in Malaysia.