Analysis Of The Influence Of The Shule River Changes On West Lake Wetland At The Dunhuang City

As one of the three largest inland rivers in Hexi Corridor,the Shule River,stretching thousands of miles,supplies water resources for the large irrigation area and about 400,000 people living in Yumen and Guazhou regions.With the economic development and population and cropland area increase,there have been significant ecosystem degradation,such as vegetation cover decrease,river and lake area shrinking,soil salinization and land desertification.The Dunhuang West Lake wetland,the largest wetland in Hexi Corridor,is the most important ecological barrier for the Dunhuang civilization.The recharge water resources of the Dunhuang West Lake wetland are upstream groundwater discharge from the Dunhuang basin,and runoff discharge from both the Shule and Danghe rivers.Recently,due to upstream water resources exploitation,the downstream of the Shule river significantly changed,even river bed disappearing,which directly resulting in no surface runoff discharge from the Shule river to the Dunhuang West Lake wetland.It will be useful for determining ecological remediation measures by investigating the relation between the Shule river evolvement and ecological degradation of the Dunhuang West Lake wetland.The evolvement characteristics of the Shule River and the driving factors have been tackled through analyzing literature results,field investigated.It is indicated that over water resources exploitation due to population and irrigation area increase,human activities on river bed are the main reasons resulting in the downstream evolvement of the Shule river.Referring to the ancient literature records,scientific investigation reports,local planning reports,and yearbooks,as well as monitoring data and remote sensing images relevant to the Dunhuang West Lake wetland,vegetation cover changes have been analyzed as well as natural ecosystem area change trend.The forcing factors in both natural and social aspects have been summarized for the ecosystem degradation of the Dunhuang West Lake wetland.It is indicated that surface water recharge to the wetland is mainly from the Danghe river before the year of Yongzheng emperor of Qing Dynasty.After that,through artificial river reclamation,the downstream runoff flowed into the wetland with confluence of the Danghe river.While it did not flow into the wetland any more during the year of Daoguang emperor of Qing Dynasty.Since 1949,there is no surface water connection between the Shule river and the wetland after the Changma and Shuangta reservoirs have been developed.The research results indicate that evolvement of the downstream of the Shule River has no significant effect to the wetland ecosystem degradation.The main reasons of the ecosystem degradation of the Dunhuang West Lake wetland are population and irrigation area increase at the Dunhuang region,which resulted in great runoff decrease of the Danghe river downstream and groundwater level decrease.Therefore,water recharge into the wetland was significantly decreased significantly.