| Water resource is the core of oasis problems. So the research spreads around water resource. The paper mainly includes three sections: The present situation analysis of water resource utilization, the scenarios simulation of water resource utilization, the analysis and estimation of oasis ecological security. Among them, present situation of water resource utilization is the basic of the study, water resource utilization scenarios simulation is core, and ecological security analysis and estimation are further prolongation and penetration of the study.In present situation analysis of water resource utilization, three means were adopted: 1) process analysis of water utilization, 2) type analysis of water utilization, and 3) water resource consumption history rebuilt based on virtual water theory. In order to ensure the reliability of the conclusion, we made extensive examinations on the actuality analysis of water resource utilization. The conclusion coming from the three ways are adjacent and the errors are not quite prominence. So it can fulfill the request of the study. In order to built ecological water demand scenarios, we introduced sand transport model (Wasson & Nanninga model), and educed the effective vegetation coverage in oasis area based on it. Using IPAT model, we analyzed and simulated 7 water resource utilization scenarios in economy and society system in the study regions. Combine ecological water resource demand scenarios and economy and society water resource need scenarios, water resource carrying pressure in Wuwei and Minqin Oasis was analyzed. In the end, in order to learn the effect of water resource utilization, emergy theory was introduced to analyze and estimate the ecological security of Wuwei and Minqin Oasis. The mainly conclusions of the study are:(1) If water resource is scarce, the competition advantages of water resource utilization among different competitors lie on space position, economic gross, population scale, development level etc. Stream water resource total planning only makes some adjustments based on them.(2) Because of the different of the competition advantage to water resource utilization, there are some obvious differences between present water resource utilization situation in Wuwei and Minqin Oasis: Wuwei Oasis occupies most of the surface water resource of the Shiyan River stream, as a result, its groundwater is not overexploited largely, ecological environment and water resource condition are better than Minqin Oasis's greatly. Although,Lacking water resource is still an important factor to restrict the sustainable development of economy, society and ecological environment of the region. Minqin Oasis mainly depends on overexploiting groundwater to maintain its water resource consumption. For the reason, its economy development was cumbered and ecological environment becoming worse and worse. New study indicates: groundwater overexploited in Minqin Oasis exceeds originally estimation. Perhaps, its ecological stabilization and sustainable development is more severity.(3) Using sand transport model, we advanced a method to get effective vegetation coverage. Effective vegetation coverage is a threshold between max-distinction coverage and inflexion coverage. So, effective vegetation coverage is not a certain value and has a change range. Effective vegetation coverage is the basic of feasible ecological scope. Under feasible ecological scope, we could get the best ecological defense by the least ecological resource investment.(4) By analysis water resource condition in different scenarios, we found stabilization was the most important in Wuwei Oasis: if it kept present development, water resource consumption would be keep stabilization; but if it quickened its economic development without water resource consumption control, water resource consumption would increase remarkably. Some methods were taken to promote saving and modulating water resource utilization, water resource consumption would come back to steady. While the means to reduce water resource use were not distinct effect. Under all scenarios, water carrying pressure kept on high level in Minqin Oasis. Although there were distinct differences in scenarios, the situation of high water resource pressure could not be changed. So, some special methods should be taken to release water resource crisis in Minqin Oasis.(5) Ecological security situation is mild improve in Wuwei Oasis, but it was not stabilization and existed rebound trend. Ecological security deterioration is very fast in Minqin Oasis. We also found the factors effecting ecological security have changed: in Wuwei Oasis, before 2000, natural factor was the main drive of ecological security, after 2001, the factor changed to economy development; in Minqin Oasis, before 2000, agriculture output was significant to ecological security, but after 2001, the same reason became the main threat of ecological security.
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