| The impact of human activities and global climate change on water scarcity and water pollution has drawn the attention of all countries in the world.With the rapid socio-economic development,human activities have a greater impact on the water resources and the quality of water environment,which is mainly reflected in the changes in land use and the changes in the hydrological cycle of the watershed,the meteorological factors changes such as precipitation and temperature also lead to changes in the mechanism of production and convergence in the basin.Water volume and water quality are the direct manifestations of environmental and ecological quality,more water,less water,dirty water,muddy water,and water ecological deterioration are the major problems in China's water security.Therefore,how to accurately assess water resources and water quality is a prerequisite for solving all water safety problems.The traditional assessment of water resources just stay in the visible water-blue water,but ignore the invisible part of the water-green water.Green water is a direct source of water for food crops and other economic crops.Therefore,studying green water and integrating it into water resources assessment is of great significance to solve the shortage of water resources and food security.In this paper,the Qingyi River Watershed(QRW)is taken as the research object to collect the meteorological data of DEM,landuse,soil and air temperature,precipitation and so on.SWAT model is constructed,use to simulate the blue-green water resources and water quality of QRW.Based on ArcGIS spatial analysis,study the change trend of blue and green water and TN?TP changes in water environment,analyze the impact of different land use and climate change on blue-green water and water quality.Get the following conclusion:(1)SWAT model constructionThe study area was divided into 29 sub-basins and 517 hydrological response units(HRUs)based on DEM.After reclassified,the land use of the Qingyi River basin was divided into 8 types,and the soil types were divided into 17 types.By querying relevant data and calculating the various types of land use,soil,and meteorological sites of attribute data,add to the SWAT model database,and establish a corresponding association table to connect the model and database,complete the construction of the SWAT model in the QRW.(2)Calibration and validation of the SWAT modelBased on SWAT Calibration and Uncertainty Programs(SWAT-CUP),using measured runoff,sediment,and water quality(TN,TP)data from Duo yingping,GuiDufu and JiaJiang,and calibrate and validate that the model simulation results more in line with the actual situation in the study area.The global sensitivity analysis results show that the three parameters that are most sensitive to runoff sensitivity are CN2,ALPHA_BF,and CANMX;The three parameters that have the greatest impact on sediment are CN2,USLE_P,and ALPHA_BF;The three parameters that have the greatest impact on TN and TP are:PHOSKD,SOL_ORGN,CN2.The calibration of runoff rate at Duo yingping was R~2 and NSE were greater than 0.6 at the calibration and validation periods,and both R~2 and NSE at the calibration and validation periods of JiaJiang runoff rate were greater than 0.8;Sediment at JiaJiang were both above 0.85 at calibration and validation periods R~2 and NSE;Rates of GuiDufu and JiaJiang TN and TP are calibration and validation period R~2and NSE are all above 0.6.It shows that the three hydrological and water quality parameters all meet the applicability evaluation criteria for simulation.(3)Response of Blue and green water for different land useAccording to analysis of land use change,the order of blue water and green water resources for different types of land use is arable land>grass land>forest land,forest land>grass land>arable land.The forest land has the largest contribution to the green water volume,and the cultivated land contributes the most to the blue water volume.Therefore,the increase in forest land area is conducive to control of ecological risk such as soil erosion,floods and droughts in the river basin;changes in TN and TP concentrations in different land use indicate that the increase in nitrogen and phosphorus load in the arable land can promote the increase,and the forest land can effectively control nitrogen.Phosphorus discharge load has a beneficial effect on improving water quality.(4)Spatial and temporal distribution of blue and green water in QRWStudying the sub-basin as a yardstick,the distribution characteristics of blue-green water resources and TN and TP from 1980 to 2010 were analyzed in terms of time and space.The blue-green water changes with time,and the precipitation in the basin is also decreasing.The monthly average distribution of blue and green water is also consistent with the change trend of precipitation.It is the least in winter and accounts for 3.85%and9.67 of the whole year respectively,the highest in summer,accounting for 57.3%and 40%of the year.From a spatial point of view,blue and green water resources are mainly distributed in the middle and lower reaches of the river basin,with the most in the middle reaches,the least in the upstream,and gradually increasing from north to south.The space conditions of TN and TP are roughly the same.From the tributaries to the main stream,the load of TN and TP is getting larger and larger,and the pollution is most serious along the main stream direction.The sub-basins of 12#,17#and 19#are particularly prominent,and their pollution load is relatively The areas with the lightest pollution,such as 1#,2#,and3#,exceed 30-40 times.(5)The impact of climate change on blue-green water and water qualityThis paper achieved future climate change through two methods,scenario setting(model weather generator)and climate prediction(NCC/GU-WG Version 2.0).The two methods show that the blue-green water resources are positively correlated with temperature and precipitation.In this scenario,the impact of precipitation on blue-green water is more significant than that of temperature;the relationship between TN,TP and temperature is positively correlated.When the temperature is high,the trend of TN is relatively stable,and the rate of change of TP is gradually increased.TN and TP were negatively correlated with precipitation,and the response of TP to precipitation changes was more obvious than that of TN. |
PDF Full Text Request