MODELING DISTRIBUTION OF BOD, DO, PHOSPHATE, AND NITRATE OF BENGAWAN SOLO RIVER IN UJUNG PANGKAH, GRESIK EAST JAVA

Bengawan Solo River is one of the major rivers that pass through several cities and empties into Ujung Pangkah, Gresik East Java. The development of industry and domestic sewage along the Solo River has affected the quality of water in the Ujung Pangkah estuary. Estuary of the river is part of the coastal region that has an important role in the economic, ecological, also areas with complex ecosystems. As a result, the flow of Bengawan Solo River flowing into Ujung Pangkah estuary causing changes in water quality, so it is necessary to model the distribution of water quality to identify whether it is in accordance with the permitted quality standards. Hydrodynamic models and water quality distribution were performed with the help of Mike 21 software, with hydrodynamic module and Ecolab module used to calculate and know the spread of BOD, DO, Phosphate and Nitrate. The tidal model of Mike 21 in this research has error 0.1%