Remote Sensing Inversion And Spatio-temporal Variation Analyses Of Water Conservation In Long Time Series

Water conservation service function plays a central role in ecosystem service function.Quantitative assessment of water conservation function can provide reference for regional ecological environment quality evaluation.Huangshan City is located in the south of Anhui Province,It has a unique geographical position and plays the role of ecological barrier to East China and even the Yangtze River Delta region.The ecological environment of Huangshan City is of special importance to the ecological security and resource support of the Yangtze River Delta economic zone,and its ecological environment quality is directly related to the ecological security of the surrounding areas.In recent years,due to the increasing intensity of natural ecosystem intervention,ecosystem structure is changing at an unprecedented speed.Therefore,the long-term monitoring of water conservation and the reveal the spatiotemporal variation of water conservation in Huangshan City can provide reference for the ecological environment planning and construction of Huangshan City.At the same time,as a demonstration area of ecological civilization in Anhui Province,the quantitative evaluation of water conservation function of Huangshan City can also provide a basis for the evaluation of its ecological engineering construction.Using technique of spatial and temporal data fusion,this paper obtained the Huangshan city in 2009-2018 monthly high resolution remote sensing data sets,inversion and analyzes ten years Huangshan city spatial and temporal variation characteristics of vegetation coverage,based on the precipitation data storage method,combined with years of rainfall,analyzed the decade Huangshan city spatial and temporal variations of water conservation function,to reveal the Huangshan city in 2009-2018 decade amount of time and space change rule of water conservation.And the importance grade of water conservation service function in the study area is divided.The above research aims to provide data and method reference for remote sensing monitoring of water conservation in a larger region,and to provide reference value for evaluation of regional water conservation function.The main conclusions are as follows:The temporal and spatial variations of vegetation coverage in the long time series(2009-2018)were characterized by the following characteristics:(1)Interannual variation of vegetation coverage:The vegetation coverage fluctuated and increased in the range of 0.72--0.8 in the past decade,with an annual mean value of 0.75 and a rate of change of 0.0076/a;(2)Spatial variation characteristics:The distribution locations of high and low FVC changed lightly in different years.The high value areas were mainly located in the central and southwestern part of Huangshan City,while the low value areas were located in the city,valley and river.In the past ten years,the area of vegetation coverage increased more than 77%of the city area,and the vegetation coverage of Huangshan City became better;(3)Change of vegetation coverage grade:During the ten years,the area proportion of vegetation coverage grade 1(0-10%)to grade 4(50-70%)decreased,and the area proportion of grade 5(70%-1)increased by2.2%.The temporal and spatial changes of water conservation in a long time series(2009-2018)were characterized by the following characteristics:(1)Spatial distribution of water conservation:During the decade,there was little difference in the distribution of high and low water conservation amount.The high value area is located at the junction of Huangshan District,Yixian County and Huizhou District,and the low value area is located in the urban area of Huangshan City.(2)Change trend of water conservation:During the decade,the average water conservation amount was 1.96×10~9 m3in Huangshan City.The change of water conservation amount was lightly in the first five years,and fluctuated greatly in the last five years.The water conservation amount was the highest in 2015 and the lowest in 2011.The water conservation amount in Huangshan increased during the decade.(3)Changes of water conservation amount among districts and counties in Huangshan City:Water conservation amount increased in most areas of Huangshan City,with the increase of more than 40 mm in Qimen and Xiuning counties,and the smallest increase of 13mm in Huangshan District.(4)Seasonal variation characteristics of water conservation amount:The water conservation amount in Huangshan City has strong seasonal variation.The water conservation amount in summer is the highest,followed by spring,autumn and winter.The contribution rate of water conservation amount in summer to the annual water conservation amount is about 50%.(5)Change trend and its significance results:From 2009 to 2018,the proportion of each state of area in Huangshan City from large to small is as follows:Significant improvement(85.2%)>slight improvement(13.3%)>slight degradation(0.04%)>significant degradation(0.026%)>basically unchanged(negligible).Significant improvement and slight improvement areas were widely distributed in Huangshan City,accounting for 98.5%of the city area.The water conservation and ecological protection project in the upper reaches of the Xin’an River,planned and implemented by Anhui Province,has achieved initial results.In terms of importance level of water conservation function,the area with medium importance of water conservation service function in the study area was the largest,accounting for more than 80%of the area of Huangshan City in 2012,2014,2017 and 2018.The water conservation amount per unit area in most areas of Huangshan City is more than 60 mm,and its water conservation service function is strong.In terms of reliability verification of the inversion results,there is a good correlation between the water conservation amount and the change trend of surface runoff in Huangshan City.Compared with the studies on the similar scale,the magnitude of the inversion in this paper is within the normal range.