Study On The Relationships Between Water Quality And Land Use Pattern In The Upper Catchment Of Xiquanyan Reservoir

Land use is one of the important driving factors for the change of water environment quality. Doing research on the change of land use and the space-time relations between it and water environment quality, is an important premise and base to ascertain change of water quality. This paper selects upper catchment of Xiquanyan Reservoir as the study area and research the LUCC of this area as a breakthrough to analyze the space-time relationship of LUCC and water quality from1986to2010. Using TM image of Landsat satellite as date source, the paper supported by GIS and RS technology respectively picked up the land using date from1986,1995,2000and2010. Meanwhile, it obtains water quality parameters of upstream from Aug.2010to Oct.2010through laboratory Physico Chemical Analysis, assesses the water environment quality of this area through Index Method-SFPIM and Grey Relevance Analysis Method-GRAM, narrates the space-time structure of land utilization changing through Landscape Index Method and Land Using Changing Analytical Mode for recent25years in this area, analyzes the space-time relations between land using and water quality in this region. The main research results are as follows:The quantity, structure, conversion characteristics and space changes of LUCC in three period in the upper catchment of Xiquanyan Reservoir indicate that:dry land is most obviously increased (net increase12284.263hm2); water area and paddy field have been also high increased; forested land is obviously decreased by16427.656hm2from1986to2010. It is high for the retention rate of forest land, Sparse Woodlot and residential area, which reaches over92%. The major transformations of dry land are forest land→dry land, shrubbery→dry land, high coverage grassland→dry land, paddy field→dry land. Dry land is mainly transformed into forest land, and the transformation of forest land has the largest construction rate. The transfer process of advanced land utilization takes70%of the whole transfer process. It can be shown in5main types:forest land→dry land, dry land→forest land, dry land→paddy field, paddy land→dry land, dry land→water area. Among these5types, the transfer process from forest land to dry land takes the highest construction rate. It respectively takes26.95%.40.69%and63.42%in the three time intervals.Using SFPIM and GRAM to evaluate water quality of8fracture surfaces in Aug., Sep., and Oct.2010, the evaluation result of GRAM illustrates that the water quality in the upper catchment of Xiquanyan Reservoir is in perfect condition, and is up to the II class of the state quality standard. However, the result of SFPIM finds out that the total nitrogen of R1-R4surface is a little bit high, which can only reach the IV level. The possible reason is, there is a great quantity of dry land and paddy field in the circum of R1-R4surface, and tending activities seriously influence water quality. The TP concentration of R5and R6just reach to the V level, because R5and R6surface is the water entrance of Xiquanyan Reservoir for the water mixed with Ashi River and Huangni River after flowing through Pingshan Town and couples of natural villages.Landscape layout of the upper catchment of Xiquanyan Reservoir has been obviously changed:irregularity of landscape patches has elevated; the number of patches has increased; the total degree of fragmentation for landscape is increased; the complexity of landscape structure is getting higher; the landscape layout is getting more diversify. Forest land and dry land become the advanced type of land use in this area. The connectivity of advanced patches is in a good condition; the collection situation of landscape in river basin is decreased.An analysis of relationship among the index of water quality parameter and landscape index of each subbasin shows:it has correlation among the parameter index of water quality in Aug. and index of each landscape, but not notable. Ammonia nitrogen and PD are positive correlation in the parameter index of water quality in Sep, and presents negative correlation with ENN_MN, ED and AI. DO and SHAPE_MN are negative correlation; BOD5and SHDI are passive correlation; TP and SHAPE_MN are passive correlation. The correlation analysis for the relation between land using rate and water quality indicates that, just in Sep., land using rate of each son basins and ammonia nitrogen (NH3) in water quality parameter present passive correlation with sparse woodlot, and present negative with paddy field. TP presents passive with others forest, and presents passive with water area.Landscape index of each subbasin’s land using presents passive correlation with NH3, CODMn and ENN_MN in water quality index in Aug; and TN presents negative correlation with ENN_MN. In water quality index of Sep, NH3presents negative correlation with LPI and COHE; and TN presents negative correlation with ENN_MN. In the index of Oct, TN presents negative with ENN_MN. In the country residential area of each subbasin, landscape index of land using is only closely related with water quality in Sep and Oct. in Sep, NH3presents passive correlation with PD and ED, presents negative with ENN_MN; and TP presents negative correlation with AI. In Oct, DO present passive correlation with AI; the same as TP and AI. The landscape index of dry land using in each subbasin have a certain relation with water quality index in Aug, Sep and Oct2010, whereas it is not notable. The landscape index of land using in each subbasin can only be closely related with water quality index in Sep. NH3presents negative correlation with COHE and AI.