Modeling the Water-ecology-land Nexus in the Dry Land Area: An Ecological Water Transfer Project in the Trim River

A lack of water may undermine the fragile ecosystem or the functioning of the food production sectors with social and economic effects in the dry land. Limited water resources should be considerable trade off the need of ecosystem and the human to keep balance between the two strategies. In the study, a system methodology was present to model the Water-Ecology-Land (WEL) Nexus, and the term Nexus designate the interactions between water, ecology and farmland. By using the cause loop diagram (CLD) and system dynamic (SD) methodology, the model of the WEL nexus had been built with integrating biophysical, social and economic, which was named WELSD model. In the process of modeling, these discussions were highlighted: (1) The flow mechanism from river to the groundwater, (2) The need of the natural vegetation, (3) Limitation of cultivated land area, (4) Effectiveness of artificial water transfer, and (5) Economic benefit evaluation. Solutions focused on equitable allocation of water across the Nexus need, then integrated knowledge on the ecosystem services provided by rivers, lakes. A case was presented in the present work: the eco water transfer in the Tarim River at the west of China. The Tarim River runs across the Taklimakan desert, and the fragile ecosystem in the river, especially in the downstream of the river, is in danger, because the flow water was decreasing, while the irrigation water increased for the agriculture development. Seventeen times ecological water transfer project had implemented in 2001-2017 years. The methodology apply to the case and modeling the water-ecology-land nexus in the region. In order to simulate the effect of the ecological water transfer process and optimize the scheme, the WELSD model of the nexus was established, which used the quality-assurance data of the project and the academic achievements from the related research. Through the case application, we find how altering one variable has consequent effects throughout the ecosystem. Options for strategic interventions to maximize benefits while minimizing negative impacts, were identified that would enable national and sub-national policy makers to take more informed decisions, across the ecology, water and food supply sectors. This approach should be further tested to see if it may aid policy making in other large river systems around the world.