Effect Of The Source-sink Landscape On Water Quality And Optimization Strategy In The Puzhehei Watershed

Based on the DEM data,using Arc GIS hydrological analysis set up 26sub-watersheds in Puzhehei of Yunnan Province.Continuous monitoring of total phosphorus（TP）,phosphate(PO₄^3--P),total nitrogen（TN）,ammonia nitrogen（NH₄⁺-N）,total organic carbon（TOC）and dissolved oxygen（DO）,and evaluation of the degree of eutrophication.On the other hand,After rasterize the interpreted landscape vector data,Fragstats3.3 software was used to calculate landscape indexes.Compare and analyze the above traditional landscape index with the“source-sink”landscape space load contrast index（LWLI）.The relationship between water quality and the landscape index was analyzed by correlation analysis,redundancy analysis,and regression analysis,for screen the indexes that can evaluate the water quality and propose landscape optimization strategies.（1）Cultivated and forest land were the main landscape types,respectively account for 50.87%and 33.94%of the total watershed area,the proportion of gardens,bare land and barren grassland was less than 2%.,The combination of cultivated land>forest land>residential land was the most in each sub-basin.（2）The average concentrations of NH₄⁺-N,PO₄^3--P and DO meet the class II water standard.TP and TN were lower than category IV water during low and high water periods,over-standard phenomenon was serious.The water quality was high water periods>mean-flow periods>low water periods,in the state of moderate eutrophication.（3）Impact of landscape composition and pattern on water quality:Cultivated land was positively correlated with TN during low water periods and PO₄^3--P in high water periods;water quality and water area are negatively correlated in everyt periods.In general,the water quality in low and high water periods was more affected by landscape composition than in normal water periods;patch density（PD）and diversity index（SHDI）were closely related to the response of water quality indicators.The relationship between LJI and water quality indicators was not obvious,and it is not suitable as a characteristic index of the landscape pattern of the watershed.（4）Correlation between location-weighted landscape contrast index and water quality:There was a positive correlation between the LWLI and total phosphorus（TP）,PO₄^3--P,and NH⁴⁺-N.It shows a negative correlation with DO,but only high-water period.There was no correlation between LWLI and TOC.Regression analysis shows that:the regression coefficient（R²）between the LWLI and TP was 0.856 during the high-water period.（5）In the process of water pollution control,in addition to reasonable planning of the landscape composition,"controlling sources and increasing sinks"was also an important Scientific method.Reducing the relative importance index of the“source”landscape and raise public awareness and actions to water protection.It can improve the water quality and delay the degradation of wetlands,promote the sustainable development of the watershed.