Theory And Model Of Water Resources Reasonable Allocation Oriented Ecology In The Shiyang River Basin

The Shiyang River basin is the region where the degree exploitation and utilization is highest and water conflict is sharpest in the inland river basin of China. The ecological water requirement (EWR) was occupied by economical water utilization because of unreasonable water resources allocation, which resulted in the serious ecological crisis in Minqin oasis, downstream of the Shiyang River basin. The research on water resources reasonable allocation oriented ecology could provide decision-making basis for the sustainable water utilization and fragile eco-environment improvement, so it has remarkable scientific significance and application value.The concept,foundational theories and allocation objectives, principle and mechanism of water resources allocation oriented ecology are proposed in the dissertation. According to the analysis on challenges from the allocation, the framework system of water resources allocation oriented ecology is established which include evolution of ecosystem controlled by water, evaluation of ecosystem value, ecological water requirement, allocation model and it's application.The evolution mechanism of ecosystem controlled by water in Shiyang River Basin is analyzed. The Probability of three types of covered grassland in different groundwater depth in Minqin basin is obtained based on the spatial distribution of groundwater depth and vegetation. Thus, the groundwater depth suited for the ecosystem could be determined. The driving forces of ecosystem evolution were analyzed through climate change and human exploitation and use on land and water resources. The result shows that the intensive human activities induce reallocation of water resources in the basin, which lead to the deterioration of water-dependant oasis ecosystem. Based on the principle of water and energy balance, the model of oasis-sized is built. The area suitable for irrigation in Shiyang River Basin is only 213,800-240,300 hm2. Presently, irrigation area is 310,000 hm2. The man-made oasis is so large that a total of 70,000-96,000 hm2 of irrigated land should be given up.Referring to the methods presented by Costanza at el, a modified coefficient of the unit area values of ecosystem services was presented. The evaluation method for dynamic value is put forward which based on the developmental coefficient and scarcity degree of ecological resources. The spatial distributions of the dynamic value and static value of the ecosystem services in Shiyang River Basin are obtained which combine the land use data with GIS tool. It is estimated that the static value of the ecosystem services in the Shiyang River Basin is $0.417 billion, equal to 0.3657 times of GDP in 2000, and show descending trends from upstream mountain region to downstream desert region. The annual dynamic value is $0.235 billion, and is larger in upstream and downstream region than in middle region. The dynamic value of the ecosystem services is a new approach in optimal allocation of the natural resources by application the research conclusion about value of ecosystem service.The ecosystem need water so that they can carry out their usual function and provide the services human are used to. The methods of Gap between Evaporation and Precipitation, Cumulated Temperature, Phreatic Evaporation based GIS and Storativity are applied to calculate the ecological water requirement (EWR) for water body of river and lake, shelter–forest ecosystem in artificial oasis, natural vegetation ecosystem in natural oasis, and restoration the ecological groundwater depth. The lowest EWR is to sustain the ecosystem structure integration, and the highest EWR is to sustain the ecosystem structure integration and normal vegetation growth. At the present, it is estimated the lowest total EWR and highest EWR in Shiyang River Basin is 0.1242 and 0.2692 billion m3 respectively, in which of 0.066 to 0.2111 billion m3 need to be allocated for ecosystem. Under the protect objective of ecosystem in 2010, the lowest total EWR and Highest EWR in Shiyang River Basin was estimated as 0.1267 and 0.2790 billion m3 respectively, in which of 0.0685 to 0.2208 billion m3 need to allocated for ecosystem under the integrated water allocation. The EWR for restoration the ecological groundwater depth was estimated as 3.5 billion m3. Under the three principles of ecosystem balance, efficiency and equity, model system of reasonable water resources allocation oriented ecological water requirement is established,which include forecast model of non-irrigation water requirement, multi-objectives decision-making model, water resources transformation model, optimal model of crop plant structure in calculated unit. The optimal model is nested in water resources transformation model, which achieves coupling of the simulated model and optimal model. Taking Shiyang River Basin as an example, the input of the model are eight water resources allocation scenarios from different measurements, such as water supply, water saving, crop plantation structure regulation,and virtual water trade. The reasonable water resources allocation scenario is provided by multi-objectives decision-making model in the Shiyang River Basin. The allocation result is that the water allocation for natural ecosystem is 104.67 million m3, and for groundwater equilibrium is 30 million m3, inflow of Caiqi section is 312 million m3, inflow of Jinchuanxia reservoir is 173 million m3, the total irrigation area is 218260 hm2, and ratio of food crop, economic crop and forage crop are 54:31:15. Food demand per person of420kg could be satisfied. The theoretical formula and simple calculation formula is provided in the dissertation. The model of reasonable water resources allocation oriented ecology is established, in which the ecological benefits and economic benefits were valued together. The objective function of the model is to maximize the total benefits. Apply the model to allocate the water resources in Shiyang River Basin. The optimal proportion between ecological water use and economic water use is obtained.Finally, the advices for further study of water resources allocation oriented ecology on theory, method, and practice were provided.