Water quality assessment of Bukit Merah Reservoir, Malaysia using mathematical modeling

Abstract

Bukit Merah Reservoir (BMR), Perak is the oldest man-made reservoir in Malaysia, situated in Kerian District, northern part of Perak, Malaysia, purposely to provide irrigation water to Kerian Irrigation Scheme (KIS) for rice cultivation. Thus, a study focuses on the determination of the current water quality status of the reservoir was conducted in November 2018 and February 2019 as a representative for the wet and dry season, respectively, in order to assist the prediction of the water quality in BMR and its impact towards the ecosystem. Five sampling stations were chosen to provide a general overview of physico-chemical profile in BMR. Physico-chemical parameters (i.e.: temperature, dissolved oxygen, conductivity, total dissolved solids, pH, and water transparency) were measured in situ whereas in the laboratory, total suspended solids, chlorophyll-a, and nutrient analysis were done in accordance to APHA (2005). The concentration of dissolved oxygen (DO) and biological oxygen demand (BOD) were simulated in a graph using Water Quality Analysis Simulation Program (WASP). Based on the analysis conducted throughout the study, the result indicated that the temperature, pH, chlorophyll-a, orthophosphate, and nitrate-nitrogen were higher in November 2018 compared to February 2019 which is 31.3°C, 6.8, 0.0533 µg/L, 0.0158 mg/L, and 0.1731 mg/L, respectively. One-way ANOVA showed that temperature and pH were significantly different between stations (p<0.05). WASP was used to validate the calculation to make sure that other parameters including DO saturation level, BOD loading, BOD decay rate, and reaeration rate values are reflected in the simulation graph. As for the initial study, this model reflects the current condition of DO and BOD level in the reservoir, but in future the reservoir should be divided into segments in order to obtain a more realistic prediction. The accuracy of the predictions can be improved with more input of water quality data.