On concepts of ecological water demand

With the increasing awareness of the importance of ecological and environmental protection,the concept of ecological water demand has been disputed among numbers of researchers mainly from the field of ecology,hydrology and water resources.In this paper,the concepts related to different aspects of the ecological water protection are discussed,including ecological water demand,the existing ecological water,the ecological water use,the ecological water shortage,the ecological eater consumed and ecological water returned.Two general relationships between the concepts are also described.It is noted that the concept ecological water demand is proposed for the ecological protection or rehabilitation as well as water resources development and utilization.While the ecological water shortage must be the most direct factor for water resources allocation if we take into account the ecosystem and environment health.The ecological water shortage can be determined based on the estimation of ecological water demand and the assessment of existed ecological water,and may be the base of ecological water use.The procedure of water resources allocation for the ecosystem is as follows.At first,the ecological object must be defined rationally according to the field investigation.Then the ecological water demand,existing ecological water can be estimated,and the ecological water shortage can be obtained.Based on the ecological water shortage and the feasibility of ecological water use,the schemes of ecological water allocation can be settled.