Water Quality Status of Omang Pond in Gunungsewu Karst Area, Gunungkidul, Indonesia

Abstract

The Gunungsewu Karst Area has a unique hydrological system with limited surface water resources, especially in dry seasons. Karst ponds, thereby, play an essential role in meeting the local water needs. Omang is a karst pond used intensively for bathing and washing, which is thought to decrease water quality. The research objectives were (1) to determine the characteristics of the pond, (2) to analyze the pond water quality, and (3) to assess the water quality status. Water quality analysis was conducted at several points selected by purposive random sampling. Temperature, pH, DO, and TDS were measured directly in the field, while nitrate, phosphate, turbidity, BOD, and fecal coliform were tested in the laboratory. Also, the National Sanitation Foundation-Water Quality Index (NSF-WQI) was employed to assess the water quality status. Results showed that the pond has a shallow depth, making the bottom sediment prone to mixing, and a volume of 4,706.09 m3. Per Governor Regulation Number 20 of 2008, DO, BOD, nitrate, phosphate, and pH exceeded their respective upper limits for class II purposes. In contrast, temperature, turbidity, TDS, and fecal coliform met the recommended standards. Based on the NSF-WQI values, the status of the pond water quality was moderately polluted.