Relationship between land use and water quality in a small watershed in South Korea

Abstract

Recent research and monitoring undertaken by various institutions have emphasized measurements of river-water quality. Based on the results, government agencies have set guidelines to improve river-water quality management. However, the relationship between water quality and land use/land cover (LULC) has not been examined closely in South Korea to date. This study investigated this relationship in the Imgok River watershed. For this study, the relationship between water quality parameters, e. g. metallic ions, biological oxygen demand and chemical oxygen demand (BOD and COD), NH3, NO3 and PO4 levels and land-use types (abandoned mine land, forest/grassland, agricultural, livestock and residential areas) was examined by correlation analysis with significant level (p < 0.05) and principal component analysis (PCA). Applying PCA to water quality parameters according to land-use coverage, the principal component impacting river water quality were found to be the pH, metallic ions, BOD, PO4, COD and total suspended solids (TSS) for abandoned mine land (AML) coverage; BOD, NO3 and PO4 for forest/grassland areas; TSS, NO3, and PO4 for agricultural land; BOD, COD, NH3 and NO3 for livestock coverage; and BOD, COD, NH3 and PO4 for residential areas. For the AML, the pH exhibited a significant negative correlation with other water quality parameters at the significant level (p, 0.05). Grassland showed significant positive correlations of BOD with values of 0.837 NO3 and 0.514 PO4. In agricultural land, TSS had a significant negative correlation with value of -0.772 PO4. For livestock coverage, BOD had significant positive correlations with values of 0.865 COD, 0.629 NH3, 0.709 NO3 and 0.472 TSS. In residential areas, COD was significantly positively correlated with values of 0.988 BOD and 0.856 PO4, and TSS was highly positively correlated with value of 0.810 NO3 but highly negatively correlated with value of -0.702 PO4. Based on the above, LULC is a significant factor to influence on river water quality and this relationship should be based on the management plan for river water quality control. Future work will be conducted to take more samples in the entire river and season, to run water quality model and to choose a new method for better analysis and more accurate relationship between land-use and water quality.