Dynamic And Correlation Between Water Quality And Land Use Pattern In The Taihu Lake Basin

Past several years, the eutrophication in Taihu Lake was exacerbated, and the non-point source pollution was more prominented. There was a important reference value to research the influence of Land-Use and Land-Cover Change on water quality and the dynamic changes of water quality itself.Current researchs focused on changes of water quality caused by changes in certain types of land use, but were lack of the influence on combination of land use types.At the same time, the study focused on a single point or a single lot, but had no enough attention on the scale of point to the surface (such as watershed or larger region).In this study, The Taihu Lake basin was taken as the study area, which was divided into 13 hydro-ecological units with respect to topography, land use and flow direction of the major hydrological systems, we wanted to study the correlation between water quality and land use pattern and the dynamic change of water quality itself from the whole basin scale,which had a important reference value on researchs on the plain area of water.The main aim of this study is to explore the relationship between land use pattern and water quality in heterogeneous landscapes. The Taihu Lake basin was taken as the study area, which was divided into 13 hydro-ecological units with respect to topography, land use and flow direction of the major hydrological systems. Correlation analyses were conducted between area proportions of different land use/cover types and water quality grade across the hydro-ecological units. The results showed that:(1) The coefficient of variation of the water quality grade was positively correlated with the proportion of the woodlands, whereas negatively correlated with the proportion of the farmlands and settlements; and the correlation reached a significant level for the settlements during the non-flood season, together suggesting that these land use types had different influences on water quality; the woodlands could improve water quality more effectively than the farmlands and settlements.(2) The water quality grade was significantly positively correlated with the area proportion of the farmlands and settlements in the flood season and non-flood season, respectively, while negatively correlated with that of the woodlands. A weak, negative correlation was found between the water quality grade and the area proportion of the wetlands in the non-flood season, whereas weak, positive correlations were shown in the flood season and the whole year.(3) The four major land use types had different strengths of improving water quality, with a ranking of woodlands>wetland>settlement>farmland in the flood season, and woodlands>farmland>wetland>settlement in the non-flood season. The woodlands presented the largest positive contribution to water quality. In contrast, the farmlands and settlements had the largest negative contribution to water quality in the flood and non-flood season, respectively.(4) The north-west of the Taihu Lake basin was the most polluted areas which had a greatest influence on water quality of Taihu Lake. Different hydro-ecological unit had different characteristics on the distribution of pollution in every month, the differences between the months of contamination distribution were not significant correlated with the flood season or non-flood season. The upstream of the basin had a better water stability than the downstream, and the water quality tend to improve in the whole basin during the Eleventh Five-Year-Plan Period, but the forest upstream the basin was the only one region who's water quality was deteriorated. Taking into account the important effect of the reservoirs on water source, it is necessary to take a more detailed study in this areaThis study identified the regions which were the most serious pollutioned and most closed to Taihu Lake; while by studying the correlation between water quality and land use pattern, revealed that different land use types had different strengths of improving water quality. The results could provide a reference for protection on water environment and wetlands.