Gatal Lake is located in the Kotawaringin Lama District, West Kotawaringin Regency, Central Kalimantan, Indonesia. The government and the surrounding communities use Gatal Lake for recreation, irrigation, livestock, and fisheries. Geographically, Gatal Lake, is close to oil palm plantations and palm oil processing factories that contributed to water pollution, especially the pollutants originating from plantation activities in the form of largescale use of fertilizers and pesticides. This study aimed to determine the status of the water quality of Gatal Lake, Kotawaringin Lama based on the physicochemical parameters. The samples from five stations were analyzed based on the following parameters: temperature, TDS, TSS, pH, BOD, COD, DO, nitrate, nitrite, phosphate, Pb, Cd, H2S, oil and grease, detergent, and phenol. The study was conducted using a purposive sampling method and determining the status of water quality based on Government Regulation No. 82/2001. The results of the physicochemical analysis of Gatal Lake showed that the water quality parameters which exceeded the water quality standards, are BOD (6.94 to 8.65 mg L), COD (9.58 to 15.7 mg/L), and DO (4.20 to 5.10 mg/L), while the parameters that did not exceed the water quality standards for Class I, II, III, and IV are temperature, TDS, TSS, pH, nitrate, nitrite, phosphate, Pb, Cd, H2S, oils and fats, detergents and phenols. On the basis of the STORET method, the water quality of Gatal Lake for Class I, II, and III are included in the highly polluted category, and for Class IV is in the moderate category.
