Assessment of water quality and pollution load in Logung reservoir, Indonesia

Abstract

The Logung Reservoir in Central Java Province is one of 18 new reservoirs developed to support the National Food and Water Security Program. Despite fully operating recently, its water quality is potentially degraded due to existing human activities surrounding this reservoir. Therefore, we conducted a study to assess water quality in this reservoir (from November 2019 to January 2020) and biological productivity status using the Trophic Level Index (TLI) based on the value of brightness, chlorophyll-a, total nitrogen, and total phosphate. The STORET technique with Class II water quality criteria is used to determine water quality based on physical, chemical, and biological characteristics. This study indicates that general water quality status is classified as class C (moderate) or moderately polluted, with a score of -18 to -20. Parameters that exceed the threshold are Biochemical Oxygen Demand (BOD) and total P, possibly due to high organic matter from residential and agricultural areas. As for biological productivity, the analysis shows that the waters of Logung Reservoir can be categorized as oligotrophic, with TLI values ranging from 2.6 to 2.8. This study should be conducted regularly since its results are useful for reservoir managers in formulating strategies to improve and maintain water quality standards so that the reservoir can function properly.