Despite numerous studies investigating the relationships between water quality and land use, there are increasing concerns about the geographical variation and lack of spatial integration in previous studies. We investigated the relationships between land use and water quality characteristics in the Hwa-Sung estuarine reservoir watershed in Korea, which has spatially integrated land uses. The spatial variations of these relationships were also examined using zonal analysis. Water quality parameter were positively correlated with residential and forest, negatively with paddy and upland especially during base flow in the near buffer zone. Population and livestock density was correlated well to water quality parameter than just number of population and livestock. Relationships across zones, distinguished by distances from streams, were inconsistent and erratic, suggesting that the relationships between remote land uses and water quality may be affected more significantly by sub-basin characteristics than by the land use itself. This methodology could be applied to other areas where the watershed characteristics are not significantly different from the study area.