Effects Of Southward Diversion Of Theyellow River On Eco-environment And Social Economy Of Xu-huai River Basin

The southward diversion of the Yellow River has had great influence on the eco-environment, social economy and people's life along its lower reaches. Subsidized by the key program of Jiangsu Social Science Funds, this dissertation applies multi-disciplinary theories and methods. It investigates the changing of eco-environment and social economy of Xu-Huai area and its interaction pattern with the southward diversion from the aspects of 1) evolution of the southward diversion of the Yellow River, 2) changing of natural eco-environment and 3) impact on social economy. The main conclusions are as following:Firstly, The historical background and southward diversion of the Yellow River at the lower reaches are discussed chronologically. And the reason of southward diversion of Yellow River is analyzed in the aspects of nature and human.Secondly, in the view of the eco-environment and social economy, effects of southward diversion of the Yellow River on Xu-Huai River Basin are analyzed. During this period, the change of the eco-environment in the area caused repeated flood, which in turn exerted great influence on the changes of the eco-environment, e.g. river diversion, formation of new lakes, siltation and disappearance of some lakes, eastern movement of the coastline and deterioration of the soil.Social and economical impact on Xu-Huai area is investigated in the aspects of agricultural economy, urban patterns and economy and social culture. The impact mainly includes the river's diversion caused frequent agricultural disasters, many destroyed agricultural irrigation projects and facilities, reverse farming system, rise and fall of cities (or even cities being flooded), marginalization of regional political position, conservativeness of social psychology and turbulent social order.Thirdly, on the basis of vast investigations, experiments are conducted on the particle size, mineral ,mechanical and chemical compositions of the typical soil profile from the former flooded areas and that from the non-flooded areas in Xuzhou. The experiments reveal in the contrast of the topsoil in these two areas, organic fertilizers and total nitrogen in the soil of the non-flooded areas are much more than those in the soil of the former flooded areas and the average pH value of the former is 7.34, the latter 8.19. The cation exchange capacity in the former soil is 1.46 times as much as that in the latter. In the contrast of the deepsoil, organic fertilizers in the soil of the non-flooded areas are 1.75 times as much as those in the former flooded areas and total nitrogen is 1.34 times as much as that in the former flooded areas. The former average pH value is 7.75, and the latter 8.31. The contrasts indicate fertility of soil in the former flooded areas is greatly inferior to that in the non-flooded areas.Fourthly, with the foundation samples of soil profile beneath the Pengcheng Square of Xuzhou City as subjects, an experiment is conducted on the environmental indexes such as magnetic susceptibility, mineral composition and heavy metal contents of the soil. The result shows: mineral composition in different samples are similar and heavy metal elements such as Cu, Pb and Zn in soil accumulated more in the ming and qing dynasties and the average magnetic susceptibility of soil samples in that period is about 2.3 times as in the previous time. It reflects grade of maturity of soil under research is comparatively low and sand-erosion in these areas is serious. It proves there is plenty of rain in Xuzhou in the ming and qing dynasties and frequent floods have profound influence on the up and down of Xuzhou City. It consequently provides experimental evidence to the overlapping of Xuzhou City.Lastly, the influence of the southward diversion of the Yellow River has extended to nowdays. With the help of the coupling theory and the evolution equations, a non-linear fitting and coupling degree analysis is made on composite index of the eco-environment and social economy of Xuzhou City from 1978 to 2005 by Matlab software. The analysis illustates distribution of coupling degree is between -90°~90°.The composite system comprises coordinated development phase, the deteriation and restoration of ecological environment phase and the balanced development phase between social economy and eco-environment. The dissertation points out a good eco-environment should be safeguarded by stable socio-environment and government policies and the development of social economy should keep pace with the protection of eco-environment.