Water quality of the Garang River, Semarang, Central Java, Indonesia based on the government regulation standard

The Garang watershed composed by three main river streams has been managed by the Regional water company of the Semarang city, Central Java for drinking water supply. A river is often polluted by domestic waste and industrial effluents. Therefore water quality of the river should be keep to meet the Government regulation standard. The study aims to analyze water quality of the Garang' river using pollution index based on the government regulation. Series data from 2010 to 2016 were derived from the Environmental and Forestry Office of the Central Java Province and sampling of water quality was taken in August 2017 from the middle of watershed area. Water quality parameters include temperature, pH, TDS, DO, COD, Phosphate, Nitrate, Chromium, Copper, Cadmium and H₂S. The research indicates that concentration of Copper has exceeds the standard of the Government Regulation No. 82 Year 2001. The water pollution index is 1.23, its means that the river is lightly polluted. Therefore the river should be managed comprehensively for sustainable uses in order to create one river one management concept. (paper)