Analysis Of The Impact Of Climate And Land Use Change On The Water Environment Of Yanghe Reservoir Basin

With the development of social economy,the shortage of water resources and the problem of water pollution have become increasingly prominent,As one of the most severe water resources in the seven major river basins in the country,the Haihe River Basin is also facing water shortage,reservoir eutrophication and many others problem.At present,the research on water resources has not only stayed at the risk perspective to analyze the impact of water cycle changes on the social economy,but on the impact of land use change and climate change on water resources and water environment.According to the study,on a long-term scale,the impact of climate change on water resources is more significant,while in the short term,the impact of land use change on hydrological changes is more prominent.Therefore,from the perspective of climate change and land use change,respectively Research on resources and water quality is of great significance.This paper analyzes the water resources of Yanghe Reservoir Basin from the perspective of blue water and green water,simulates the water resources status of the basin by SWAT mathematical model,and analyzes the impact of land use change and climate change on water resources in the basin through scenario setting.The effect is to select the Dongyang River Basin with relatively complete pollution discharge data as the research area.The SWAT and WASP models are used to calculate the pollution load and river water quality of the watershed.The specific research results are as follows:(1)Statistical analysis of the characteristics and trends of climate change and land use change in the Yanghe Reservoir Basin from 2010 to 2017.The climate change mainly analyzes the characteristics of precipitation changes.The statistical results show that the average annual rainfall of the reservoir basin is 610.05mm,and the annual rainfall trend fluctuates greatly.In 2012,the rainfall peaked and the annual rainfall reached 1046mm.The annual rainfall was mainly concentrated in June to September,accounting for the total annual rainfall.More than 80%,the spatial distribution of rainfall in the basin is less change;the land use type of the basin is mainly cultivated land and forest land,and the cultivated land type accounts for more than 30%and has an increasing trend year by year.The cultivated land area increased by 166.61km~2 from2010 to 2017.The growth rate reached 67.78%,the annual average of forest land was30.29%,and the grassland was 19.98%,and both of them had a downward trend.Other land use types changed little and remained basically stable.(2)Based on the SWAT distributed hydrological model,the blue and green water volume of the basin was simulated and calculated.The model simulation accuracy was good,R~2=0.98,Ens=0.90.According to the analysis of the simulation results,the water resources of the Yanghe Reservoir Basin are mainly green water,accounting for83.20%of the total.In the green water,the green water flow accounts for the main part of the green water.The green water flow in the basin is about 7.17 times the green water reserves.From the perspective of inter-annual change,the inter-annual change of blue water is significantly affected by precipitation.Correlation analysis calculates that the correlation coefficient between blue water fluctuation and precipitation fluctuation from 2010 to 2017 is r=0.86,and the correlation coefficient between green water fluctuation and precipitation fluctuation is Only r=0.40,it can be seen that blue water in the basin is more susceptible to rainfall.In the change of green water,the correlation coefficient of green water flow fluctuations r=0.98 and the correlation coefficient of green water storage fluctuations r=0.64.Is affected by changes in green water flow.The intra-annual variability is similar to the inter-annual variability.(3)The results of land use impacts show that the annual average total blue water resources of the Yanghe Reservoir Basin is 99 million m~3,and the spatial distribution is mainly concentrated in the lower reaches of the river and the surrounding areas of the reservoir(463.74mm)is about 2.96 times the average blue water(156.53mm)of the basin;the annual average total green water resources in the basin is 438 million m~3.The green water is mainly concentrated in the Dongyang River,Miwu River,and Maguying River Basin,and the average annual green water volume of Maguying River Basin is646.78mm,which is about 1.24 times that of the Xiyang River Basin(520.28mm).The spatial distribution characteristics of green water flow are consistent with green water.The spatial distribution of green water storage is affected by many factors such as reservoir replenishment and landuse.The green water reserves(157.12mm)in the surrounding sub-basin are about 2.12 times the average green water reserves(73.97mm)in the basin,and the green water reserves in the Dongyang River Basin are about 1.14times that of the Xiyang River.In terms of interannual changes,changes in water resources and land no significant change in utilization patterns.(4)SWAT pollution load simulation results show that the pollution load of cultivated land and residential land in the basin is relatively large,and the annual average unit area load of cultivated land is 5626.164t/ha,accounting for 99.5%of the total nitrogen load of all land use types.The main source of nitrogen pollution load,the pollution load level of cultivated land and residential land has a tendency to gradually decrease with the increase of the slope of the terrain;the WASP model results show that the water quality of the Botangou tributary is the worst in the basin,and the total nitrogen and organic nitrogen pollution.The highest concentration,the average nitrogen concentration of total nitrogen is 12.62mg/L,organic nitrogen is2.81mg/L.The concentration of organic nitrogen in the tributaries of Chengjiagou is the lowest,the average mass concentration is only 0.73mg/L;the total nitrogen concentration in the tributaries of Liangjiawan is the lowest,the mass concentration is only 1.67mg/L,and the storage concentration index is higher than the requirements of the III water standard.