Water Pollution Index of Batujai Reservoir, Central Lombok Regency-Indonesia

Batujai reservoir is located in Central Lombok Regency, Indonesia. The government and local people use it for hydropower generation, drinking water, agricultural irrigation, fish farming, and tourism. The phenomenon of growing population and increasing industrial activities in the catchment area of Batujai reservoir always result in the discharge of various pollutants into the aquatic environment and cause the blooming of water hyacinth over almost 30% of the reservoir area. The aim of this study was to determine the water pollution index of Batujai reservoir. The samples were analysed for the following parameters: pH, temperature, DO, COD, BOD, TSS, and heavy metals. The research was done by using purposive sampling method and determination of water quality status with STORET method based on Government Regulation No. 82/2001. The measurement results show that the physical and chemical parameters of the Batujai reservoir water do not exceed the quality standard are the temperature (29 to 32°C); pH (6.6 to 7.5 mg/L); nitrate (0.421 to 0.546 mg/L); Cd (0.0005 to 0.005 mg/L); Cr (<0.001 to 0.018 mg/L); and the parameters that exceed quality standards are DO (3.8 to 4.9 mg/L); BOD (3.03 to 4.21 mg/L); COD (6.8 to 10.1 mg/L); phosphate (0.181 to 0.237 mg/L); and Pb (0.14 to 0.24 mg/L). The water quality status of Batujai reservoir was heavily polluted for standard quality on class I, II, III and moderately polluted for class IV.