Study On The Impact Of Land Use Pattern On River Water Quality In Yangzhou City

In recent years,with rapid urbanization process,the yangzhou city underlaying surface radically changes according to the surface,grass land,wetland,water,and so on has the control function of the ecological space is gradually occupied by a right to use construction land,opaque surface increase interfere with the hydrologic cycle process,affect the connectivity of urban river water system,poses a serious threat to water environment quality.In this context,it is particularly important to study the evolution trend of land use pattern and water environment in yangzhou city,and to analyze the response relationship between river water quality and land use pattern on this basis.Based on the land use data and water quality monitoring data of yangzhou urban area in 2010 and 2020,this paper quantifies the response of river water quality to land use pattern through statistical analysis.The results show that:1.The most significant responses to urbanization are urban land,rural settlements and paddy fields.Urban land is characterized by agglomeration and development at the cost of occupying paddy fields.Rural residential area belongs to discrete expansion;Arable land（paddy field,dry land）transfer area far exceeds the transfer area,accounting imbalance.Under the high intensity of human exploitation,the degree of landscape fragmentation increases,but the landscape tends to be regular.The leading role of paddy field and water body as the dominant land type weakened;The aggregation degree of various land types improves the overall connectivity of landscape.2.The interannual variation of coverage frequency of large water bodies is not significant,while that of small water bodies is obvious.This variation rule also applies to the seasonal variation of water bodies within a year.From 2010 to 2020,the situation of water quality gradually changed for the better,and the indexes contributing more to water pollution are total nitrogen and total phosphorus.The seasonal differences of some water quality indexes were not obvious,indicating that point source pollution and industrial and agricultural activities without seasonal discharge law were also important restricting factors of water quality except the non-point source pollution which was greatly affected by seasonal precipitation.There was significant correlation among all the indexes,and the distribution difference of total phosphorus and ammonia nitrogen was the greatest in each section.3.The correlation of land use pattern water quality in flood season is better than that in non-flood season,indicating the important way of precipitation runoff source pollution.Cultivated land（paddy field and dry land）,water body and construction land have the most significant impact on water quality.Paddy field and construction land have a significant negative correlation with water quality,while water body and dry land have a positive correlation.The correlation between landscape pattern index at landscape level and water quality was most significant at 1000 m buffer scale.Patch density,edge density and aroma diversity index were significantly positively correlated with water quality,while sprawl index was significantly negatively correlated with water quality,indicating that the increase of landscape fragmentation,heterogeneity and diversity could effectively improve water quality.