Analysis Of Evolution Of Water Resources In The Mississippi River Basin Under Changing Environment

The most sensitive influence of global changing is watershed hydrological cycle,especially the great river hydrological cycle have a markedly significant effect on the global changing.In recent decades,changing of watershed hydrological cycle has deeply changed water resource in the basin,and the influence of human activities,which has effected on spatial and temporal of the global water resources.Traditionally,only gravity water is used as a resource for water resource evaluation.With the development of science and technology and the changing of environment,the significance of non-gravity water resources is gradually emerging.Under the changing environment,it is of great significance for the development and utilization of water resources to clarify the quantity of the generalized water resources,to accurate evaluation of the generalized water resources and to scientific analysis the evolution law of the generalized water resources.The study of watershed generalized water resources can also be helpful for the development of water resources theory.This paper considers the role of non-gravity water(green water)in the development and utilization of water resources,and interprets the concept of generalized water resources in the basin.Based on the GIS,combined with mathematical statistics and distributed watershed hydrologic model,the spatial characteristics changing of hydrological cycle and underlying surface was analyzed,on this basis,the watershed hydrologic model was constructed,The present situation(2013)and the history period(1980~2012)of the Missouri River and Ohio River basin in the different climate zones of same basin of the generalized water resources,green water depth,blue water depth and the green water coefficient were simulated and analyzed.The effects of different scenarios of underlying surface and artificial water use on the water resources were simulated and identified.The main contents are as follows.(1)The annual precipitation in the Southeast area is much more than the Northwest area.The eastern and western region's trend and cycle is longer than the central region.The high and low longitude regions' mutation time is delayed to the medium longitude areas.The streamflow of the Mississippi River is increasing from border area to central area.The annual sea outflow is decreasing.In 1976,the discharge is increased,in 2004,the discharge is reduced.The main period is 5a,and the sub-period is 10 a.The inter-annual variation of the runoff coefficient is basically the same trend as the runoff.(2)The main land cover is grassland,cropland,and forest in the Mississippi river basin from 2001 to 2013.To 2025,forest trend is unchanged,however,the grassland and wetland are increased.The human disturbance in the basin is greater;the low cover area shows a trend of decreasing and then increasing,and the middle cover area is decreasing,and the middle-high cover area shows a trend of increasing and then decreasing,and the high cover area is increasing.(3)In 2013,the distribution characteristics of generalized water resources in Missouri river basin shows outline high and middle low,green water depth is decreasing from the northeast to the southwest,most area of the green water coefficients are above 0.77,green water in the basin is the dominant.The generalized water resources in the Ohio River basin shows the high value are larger,small green water depth in the middle,top and bottom,blue water depth is increasing from north to south.Blue water in the basin is the dominant.The relative changes of blue and green water in the two basins tended to be stable during the year.(4)From 1980 to 2013,the annual average generalized water resources in Missouri river basin are high in the northwest and southeast areas and low in the middle areas.Annual average Green water depth are under 2500 mm,the annual average blue water depth are relatively higher in the northwest areas and lower in the southeast.Annual average green water coefficient shows a trend of increasing from northwest to southeast.In1987,the generalized water resources is highest,blue water depth is higher,and green coefficient is relatively lower.In 2001,the generalized water resources is lowest,green and blue water depth are also lower.The annual average generalized water resources in the Ohio River basin are generally low in the middle areas and periphery areas are high.The green water depth is high in the northeast and low in the southwest.The blue water depth is low in the middle areas and periphery areas are high.The green water coefficient is the opposite of the spatial distribution characteristics of the generalized water resources.In 1994,the generalized water resources is highest.The changing is more intense from 1997~2000.In 2000,the generalized water resources is lowest,and green,blue water depth are relatively lower.In general,the green water coefficient is concentrated between 0.5~0.7.(5)From 2001 to 2013,The changing of underlying surface makes that the generalized water resources and most sub basin of the green water depth in Missouri river are increased,the sub basin of blue water depth are decreased,and green water coefficient l showed a trend of decreasing;The generalized water resources,green water depth and blue water depth in the Ohio river basin are decreased,and the green water coefficient in the basin is increased.From 2001 to 2010,changing of artificial water use makes that the generalized water resources and green water depth in Missouri river basin are increased,the high value of blue water depth and green water,coefficient are decreased.The generalized water resources,green water depth and green water resources coefficients showed a trend of decrease,but the blue water depth is increased.But the spatial distribution characteristics of two watershed are basically tended to unchanged.