Assessment of water quality conditions in the Upper Johor River Basin

Abstract

The water quality data from 2 sampling stations in the Upper Johor River Basin (Upper Johor River and Sayong River) were analysed to evaluate the water quality conditions. The variation in water quality parameters between base and storm flow events were compared to identify the pollutant sources. The results indicated that Biochemical Oxygen Demand (BOD) was the main cause for non-point source pollution of the study area. The overall water quality conditions were good in terms of dissolved oxygen and total nutrients (Nitrogen and Phosphorus). The dominant sources of BOD could be from the fertiliser timing and application. Different from BOD, the majority of the water quality samples were from baseflow events for dissolved oxygen, total nitrogen and total phosphorus. The major differences between four water quality parameters are failing septic system, oil palm mills, wastewater treatment plants and domestic waste. The results from this research would provide useful information for total maximum daily load calculation, establishment of watershed and nutrient model, and development of Best Management Practices for the Upper Johor River Basin and comparable study area.