Distribution of Water Pollution SubBengawan Solo Upstream Watershed on Central Java in 2020

Abstract The Bengawan Solo watershed is included in the 15 priority watersheds that must be restored because it is one of the 108 critical watersheds in Indonesia. It is indicated that the Bengawan Solo Hulu sub-watershed is experiencing pollution and water quality degradation due to the population growth rate and various community activities around the watershed area. This research was conducted to study pollution and water quality using a spatial approach in the Upper Solo Bengawan sub-watershed in the Central Java region. The research was conducted using the Pollution Index method and Geographically Weighted Regression (GWR) modeling using BOD, COD, TSS, TDS, DO and Phosphate parameters. The results of the Pollution Index carried out show that 5 sample points are included in the category of light pollution quality and 8 sample points are moderately polluted. The lowest pollution index value is 2. 87 at point 3 of the Upper Samin River area, Karanganyar Regency. The highest pollution index value is 7.5 at point 9 in the Lower Premulung River area, Surakarta City. The results of GWR on the dependent variable BOD show that the DO variable has the most significant effect. In the dependent variable COD, the BOD variable has the most significant effect. The TDS and Phosphate variables have the most significant effect on each dependent variable and the DO dependent variable shows that the BOD variable has the most significant effect compared to other variables. In the dependent variable COD, the BOD variable has the most significant effect. The TDS and Phosphate variables have the most significant effect on each dependent variable and the DO dependent variable shows that the BOD variable has the most significant effect compared to other variables. In the dependent variable COD, the BOD variable has the most significant effect. The TDS and Phosphate variables have the most significant effect on each dependent variable and the DO dependent variable shows that the BOD variable has the most significant effect compared to other variables.