Seasonal Water Quality Upstream of Dahuofang Reservoir, China - the Effects of Land Use Type at Various Spatial Scales

Inappropriate land use is considered a main factor in the deterioration of water quality. The relationship between land use and water quality (RLW) is complex, so the exploration of how seasonal water quality is affected by land use at various spatial scales can benefit our understanding of the RLW. We examined data for 110 sampling sites upstream of Dahuofang Reservoir in China. RLWs in three seasons and at three spatial scales were analyzed via Spearman's rank correlation coefficient. After excluding unreliable data attributed to point source pollution and spatial autocorrelation, we found that land use in the riparian zone within 100m of the river was correlated with water quality during the rainy season. Taking into account the influences of spatial pattern of the land use on water quality, breakpoint regression analysis indicated that when fragmented forest land covers more than 37% of the local riparian zone, the deterioration of water quality will be mitigated, in contrast water pollution would be exacerbated when un-fragmented dry farmland exceeds 54%. Therefore, when analyzing RLW, selection of the appropriate spatial scale and season as well as improvement of land use patterns can facilitate rational and effective basin management.