Impacts Of Climate Change And Human Activities On Blue And Green Water Resources In Tanghe River Basin

Climate change and human activities are two important factors that affect the hydrology and water resources of the basin.Water resources are divided into blue water and green water in ecological hydrology.Blue water refers to the"liquid water"of rivers,lakes and aquifers,that is,"visible water".Green water refers to the"gaseous water"that vegetation returns to the atmosphere through absorbing precipitation evapotranspiration,that is,"invisible water".Green water resources account for the vast majority of available water resources.More than 80%of the water used by global food production and woodland grassland depends on green water.In recent years,the research on green water resources is gradually increasing.It is beneficial to the planning and management of water resources by studying the temporal and spatial changes of green water and blue water resources,determining the relationship between ecological and hydrological processes,conducting scientific and comprehensive evaluation of water resources.Tanghe River Basin is a typical temperate continental monsoon basin in northern China.In this study,Mann Kendall abrupt test and cumulative anomaly method are used to study and analyze the meteorological and hydrological changes in the basin from 1970 to 2015.The SWAT model is established to simulate the hydrological cycle of Tanghe River Basin,quantitatively evaluate the spatial and temporal distribution of runoff,blue water and green water resources in different time scales,and distinguish the impacts of climate change and human activities on the blue water and green water resources in Tanghe River basin through scenario analysis.The results show that:(1)On the interannual scale,the precipitation and runoff of Tanghe River Basin has a slight downward trend,with the rates of 11.48mm/10a and 45.26m³/10a,respectively,which do not reach the significant level(P>0.05);the annual precipitation and runoff has an abrupt change in 1976;the nonuniformity coefficient of precipitation shows an insignificant upward trend,while the nonuniformity coefficient of runoff shows an insignificant downward trend.On the intra annual scale,the proportion of summer precipitation and runoff in the whole year is the highest,and the proportion of both has no significant upward trend in recent years.The proportion of winter precipitation and runoff in the whole year is the lowest,and the proportion of precipitation has no significant downward trend in recent years,while the proportion of runoff has no significant upward trend,and neither of them has reached a significant level.(2)The SWAT model of Tanghe River Basin is constructed by using the data of meteorology,hydrology,topography,land use and soil to establish spatial database and attribute database,and dividing Tanghe River basin into 44 hydrological response units.10 parameters which are sensitive to the simulation results are selected to calibrate and verify the model.Taking 1970-1973 as the periodic rate period and 1974-2015 as the verification period,the E_nsand R² of the two hydrological stations in Tanghe River Basin during the periodic rate period and the verification period are all above 0.70,and the simulation accuracy is high,which can accurately describe the hydrological cycle process of the basin.(3)The average annual water resources in Tanghe River Basin are 759.37mm,and the annual average green water resources are 516.83mm,of which 176.50mm green water flow,340.33mm green water storage and 242.55mm blue water resources.The annual average green water coefficient is 68%,and the annual green water resource is 2.13 times of the blue water resource;the abrupt year of blue water and green water is consistent with precipitation and runoff,which are all in 1976.From the spatial distribution,the green water flow,green water storage and blue water resources are more than south and North,and the spatial distribution difference of green water flow and blue water resources is obvious in different seasons.(4)Under the influence of climate change,green water flow increased by 24.84 mm/a,green water storage and blue water decreased by 46.84 mm/a and 46.53 mm/a respectively,and green water coefficient increased by 0.2.Under the influence of human activities,green water flow and green water storage increased by 57.54mm/a and 198.61mm/a respectively,blue water decreased by 4.74mm/a,and green water coefficient increased by 0.1.Under the comprehensive influence of climate change and human activities,the green water flow and green water storage increased by 82.38mm/a and 151.77mm/a respectively,the blue water decreased by 51.27mm/a,and the green water coefficient increased by 0.3.Human activities have a greater impact on the green water resources in Tanghe River Basin,while climate change has a greater impact on the blue water resources.