Abstract:The study of eco-environmental water requirements is the hotspot of ecology and water science. It is also the basis of the rational allocation and sustainable utilization of water resources. The results of such a study could provide guidance as to the optimal allocation of regional water resources and utilization, and ultimately provide a regional, economical, ecological, and environmental water system of balanced and sustainable development. The eco-environmental water requirements of an arid inland river basin are a key scientific problem facing the reasonable allocation and management of water resources as well as the eco-environmental protection and construction of arid regions. The Shulehe River Basin, as the third largest inland river basin in Hexi Corridor, Gansu province, is an important ecological security barrier for northwestern China. Recently however, increasing human activity and global climate change has led to a series of ecological and environmental issues and water crises in Shulehe River Basin. Specifically, the degenerated vegetation caused a rapid decline of the groundwater water table. In recent years, ecological water requirements have often been overshadowed by the socioeconomic use of water. This led to great changes in the oasis of the middle reaches. The oasis of the middle reaches, as a societal, economical, and human activity main zone, is a vital ecological subject for protection in the Shulehe River Basin. Considering these issues, this study utilized the oasis of the middle reaches of Shulehe River Basin as its study area. Using Remote Sensing (RS) and Geographic Information System (GIS) technology, the results of Thematic mapper/Enhanced Thematic Mapper (TM/ETM) images of the oasis of the middle reaches of the Shulehe River Basin in 1990, 2000, and 2013 were selected to be used as basic data in order to study ecological evolution, and determine the ecological protection target of the oasis of the middle reaches of the Shulehe River Basin in 2020 and 2030. According to different types of eco-environmental water requirements in the oasis of the middle reaches of the Shulehe river basin, a quantification model for such water requirements was established and the current status and protection targets of eco-environmental water requirements were estimated. This would provide reference for the rational allocation of regional water resources and the coordinated development of an ecological system. These results indicate that the eco-environmental water requirements of natural vegetation, basic eco-environmental water requirements, transportation sand eco-environmental water requirements, recharge of watercourse seepage water requirements, water surface evaporation eco-environmental water requirements, marsh eco-environmental water requirements and combating salinization of farmlands eco-environmental water requirements of the oasis of the middle reaches of the Shulehe river basin were 1.90×108, 0.98×108, 1.11×108, 0.83×108, 0.68×108, 2.70×108, 0.20×108, 2.24×108, 0.98×108, 1.11×108, 0.83×108, 0.73×108, 3.13×108, 0.20×108 m3 and 2.47×108, 0.98×108, 1.11×108, 0.83×108, 0.80×108, 3.71×108, 0.20×108 m3 in 2013, 2020 and 2030, respectively. At the same time, the maximum of eco-environmental water requirements, minimum of eco-environmental water requirements, and optimum eco-environmental water requirements of the oasis of the middle reaches of the Shulehe river basin were 7.42×108, 7.09×108, 7.29×108, 8.24×108, 7.91×108, 8.11×108 m3 and 9.12×108, 8.79×108, 8.99×108 m3 in 2013, 2020 and 2030, respectively. The annual variation of eco-environmental water requirement was concentrated mainly from May to August and proportion of cumulative eco-environmental water requirements of the total ecological environment water demand were 58.01%, 58.08% and 58.13% in 2013, 2020 and 2030, respectively. The water requirements of Guazhou County eco-environmental water requirements were relatively greater than those of Yumen City and Dunhuang City. The study results will provide a basis for the management program of Dunhuang water resources reasonable utilization and ecological protection. Additionally, it will be an important source for promoting the research of ecological water rights, allocation of water quantity, and coordinated and sustainable development among ecological protection, reasonable configuration of water resources and economic society in Shulehe river basin. http://www.ecologica.cn
