Study On Impact Of Landscape Pattern On Green Water Resources In Taizi River Basin Based On SWAT Model

Water resources in terrestrial ecosystem can be divided into blue water resources and green water resources.Green water refers to the water absorbed by plants and produced by transpiration of plant leaves or evaporation of soil in the process of atmospheric precipitation.This part of water can be regarded as actual evapotranspiration.Green water is very important for crop production and terrestrial ecological environment,and it is an important guarantee of world food security.Therefore,it is extremely important to study the spatial and temporal distribution of green water resources and the impact of landscape pattern on the distribution of green water resources.This paper takes Taizi River Basin as the research object,uses the distributed hydrological model SWAT(soil and water assessment tool)to simulate the hydrological process of the basin from 1959 to 2019,estimates the amount of green water resources,and analyzes its spatial and temporal distribution in long time series and the impact of landscape pattern on the distribution of green water resources.The specific research contents and results are as follows:(1)The land use patterns in Taizihe River basin are mainly forest and farmland,accounting for 54.6% and 31% of the total area of forest and farmland,followed by construction land and water body,accounting for 10.2% and 2.6% of the total area of construction land and water body,and grassland and unused land account for the least,accounting for 0.7% and 0.1% of the total area of grassland and unused land.From the perspective of spatial distribution pattern,forest is mainly distributed in the east and south of Taizi River basin,while cultivated land is mainly distributed in the southwest and northwest.Construction land is distributed along both sides of the river and concentrated in the middle of the basin.(2)According to the DEM data,land use data and soil type data of Taizi River basin,the spatial database is established,and the attribute database is established by using soil physical data and meteorological data.The basin is divided into 90 sub basins and 645 hydrological response units.The sufi-2 algorithm is used to calibrate and verify the model parameters.The results show that the determination coefficients R2 of 7 hydrological stations are greater than0.5,and the ENS coefficients are greater than 0.5,which meet the applicability standard of the model and can accurately describe the hydrological cycle process of the basin.(3)From 1959 to 2019,the change trend of total green water,green water flow and green water storage in Taizi River basin is consistent with precipitation,and there is no significant increasing or decreasing trend in general;the green water resources have a sudden change in1972.The total amount of green water and green water flow in the four seasons are the most in summer and the least in winter.The average value of green water resources in summer is618.54 mm,and the average value of green water resources in winter is 375.62 mm.In terms of spatial distribution,the total amount of green water and green water flow decrease gradually from southeast to northwest,and the green water reserves decrease gradually from all sides to the middle.On the whole,the amount of green water resources in the upper reaches of the basin is slightly larger than that in the lower reaches,and the sub basins close to the main river channel are slightly larger than other sub basins;the distribution of green water resources and green water flow in the basin is uneven in the year,with the average value of non-uniformity coefficient of green water resources being 0.083,the average value of non-uniformity coefficient of green water flow being 0.3,and the distribution of green water reserves being more uniform in the year,with the average value of non-uniformity coefficient0.055.(4)The results showed that the landscape level index,patch number NP,patch density PD,landscape segmentation index DIVISION had significant negative correlation with the amount of green water,and the correlation coefficients were-0.25,-0.33,-0.49,respectively;the boundary density ED,maximum patch index LPI had significant positive correlation with the amount of green water,and the correlation coefficients were 0.64,0.32,respectively.The landscape and type composition of forest,farmland and grassland have great influence on the distribution of green water resources,followed by construction land and unused land.