Riparian Land-Use Change and Selected Water Quality Parameters in the Upper Brantas River: A 10-Year Buffer Zone Analysis

Land-use changes and human activities continue to pressure the upper Brantas River. This study investigated land-use change within a 200 m river buffer from 2014 to 2024 and checked its patterns to water quality along the Upper Brantas River. Selected indicators for domestic wastewater, organic pollution, and nutrient input were chosen. Land use was mapped from satellite imagery using ArcGIS, while water quality was evaluated according to Government Regulation No. 22/2021. Paired t-test and Spearman's correlation were used to check the differences and relationships among land-use proportions, individual water quality parameters, and the Pollution Index (PI). Principal Component Analysis (PCA) was used to describe spatial patterns of pollution. Natural areas decreased significantly (p = 0.022), while urban areas increased significantly (p = 0.014). Agricultural land also increased, but not significantly (p = 0.152). Several parameters exceeded regulatory thresholds: NH3, COD, BOD, TSS, and total coliform, especially in the upstream segments between SLK and BTU stations (PI = 4.42-4.68). Most Spearman correlations were not significant, except for a positive correlation between urban land and NO3 (ρ = 0.683, p = 0.042). PI showed no significant correlation with land-use proportions. PCA indicated water quality varied by location and pollutant type. These findings suggest that river management should not rely only on PI or broad land-use proportions. It should also include parameter monitoring, runoff control, and local pollution-source management.