The Influence Of Fragmentation Landscape Pattern On Water Quality In Karst Plateau Area

The research on water resources in the central of Guizhou is a hotspot in the field of karst ecological environment.In recent years,during the accelerated development of social economy and urbanization in Central Guizhou Economic Zone,the land landscape changes dramatically.Therefore,it is of theoretical value and practical significance to carry out the research on the impact of landscape pattern of the river basin on water quality.Pingzhai Reservoir is the only water source reservoir in central Guizhou Hydraulic Project area,located in a typical karst plateau,the surface landscape is broken.It is of vital importance to pay attention to the water quality status of Pingzhai Reservoir and improve the ecological environment in the basin for the water security of the whole central Guizhou region.Based on remote sensing image data(2018)and digital elevation model(DEM)data of precision of 30 m.ENVI5.3,Arc GIS10.2 and Fragstats4.2 platforms are used to obtain the landscape type composition characteristics and landscape pattern index data of Pingzhai Reservoir Basin.In this study,7 water quality monitoring points were set up in Pingzhai Reservoir,and 6 water quality indicators,including EC,DO,TP,TN,NH3-N,COD,in three periods of low-flow,mean-flow and high-flow were selected to sample and monitor,through Pearson's correlation analysis,multiple stepwise regression analysis and redundancy analysiswere used to investigate the effect of landscape pattern on water quality in Pingzhai Reservoir Basin.The main conclusions are as follows:(1)The main landscape types of Pingzhai Reservoir Basin are forest and farmland,accounting for 78.65% of the total basin area.On the scale of buffer zone,with the increase of buffer radius,the percentage of farmland and forest increases,and the percentage of urban decreases.At the level of type,PD and PAFRAC of urban are larger.At the landscape level,as the spatial scale increases,LPI changes little,while ED,LSI and CONTAG gradually increase.(2)In Pingzhai Reservoir DO and NH3-N can basically meet the standard of class ? water of surface water environment quality standard in GB3838-2002.TP,TN and COD exceed the standard in some sections of the time.The water quality of mean-flow period was better than that of low-flow period and high-flow period,and the water quality of monitoring points BS and NY was poor.(3)Effect of landscape type on water quality: the correlation between water quality index and landscape type in low-flow period is more complex.TP,TN and NH3-N are positively correlated with farmland,COD is positively correlated with farmland and urban,EC is positively correlated with urban and unuse,and DO is not significantly correlated with landscape type area percentage.(4)Impact of landscape pattern on water quality: PD of forest,grassand urban is positively correlated with EC,TP,TN,NH3-N and COD.PAFRAC of farmland and grass has a greater impact on water quality.EC and TN are significantly affected by PAFRAC of landscape type.The relationship between water quality and landscape pattern index at the landscape level is the most complex.ED and LPI are two landscape pattern indexes that have a great impact on water quality at the landscape level.Most water quality indexes are positively correlated with LPI,ED and LSI,and negatively correlated with CONTAG.