WATER QUALITY AND TROPHIC STATUS IN WIDAS RESERVOIR, EAST JAVA, INDONESIA

Widas Reservoir is a multifunctional resource with potential for fisheries, but its water quality can be significantly affected by various activities. This research aims to determine the status of trophic levels and water quality, which is crucial for water resource management and conservation. The study involved a comprehensive field survey with sampling at various points, considering the inlets, outlets, and conservation zones. The research found that the average water depth was 10.9 meters, transparency was 511 centimeters, CO2 concentration ranged from 0.0 to 17.6 mg/L, DO ranged from 0.1 to 8.2 mg/L, and temperature ranged from 25 to 31.1°C. In addition, temperature and DO decrease with depth, in contrast to CO2, which tends to increase with depth. The average conductivity was 150.3 μmhos/cm, total alkalinity was 103.1 mg/L, turbidity was 63 NTU, pH ranged from 6 to 8, and phosphate (PO4) concentration averaged 28.74 μg/L. TP average was 33.39 μg/L, and Chlorophyll-a averaged 21.75 μg/L. The Trophic Status Index (TSI) showed a high fertility (eutrophic) level with an average index value of 63.8. The potential for fish production was high at 626.6 kg/ha/year.