| Ecological water requirement is an important part of water resources allocation in the river basin, and it is the basic water requirement to ensure the ecological system staying healthy and stable and palying normally. Under the condition of modern production and living water demand growing, there has been a lot of cases squeezed out ecological water requirement by production and living water requirement. Therefore, studying ecological water requirement and guaranteeing it can reach a certain ecological requirement, and they are important conditions for the river basin water resources reasonable allocation.Hanjiang River Basin in Hubei Province is a developed area in industry and agriculture, and its population concentrated and water resources are abundant. However, because of the influence of the Middle Route Project of South to North Water Transfer Project, the inflow will be reduced in the watershed, so ecological water requirement in the watershed will be affected, thereby, affecting the ecological health of water shed. Therefore, this article set up two scenarios, including no water transfer and water transfer, studying the future ecological water requirement of the watershed under two scenarios respectively, and comparing their differences.In this paper, the calculation of ecological water requirement is based on the area of each land use type in the future, therefore, the first thing is to simulate the change of land use in the future. Simulation of land use change based on CLUE-S model, the model take on high accuracy on the small and medium scale.Wesimulate6land use types change in the next30years under the two scenarios using the CLUE-S model. The main processes are as follows:After processing the data for CLUE-S model on Arcgis platform, converting all data to ASCII file that model can identify by the conversion tool in CLUE-S model. All files needed to put the model folder, and running the model, then obtaining the land use situation in the future30years under two scenarios. The obtained results should be put in the Arcgis software, and convert the land use map.According to the simulation results, the river basin ecosystem mainly be divided into farmland, forestland, grassland, urban and water the five categories. Where ecological water requirement of forestland, grassland, and farmland system based on the land use area from the simulation of the model, public green area dominate the urban system ecological water requirement, water system is mainly calculated by using Tennant method and minimum monthly average runoff method. After calculate the ecological water requirement of each subsystem, according to the principle of integration of ecological water requirement, the ecological water requirement of whole basin system can be calculated. Research’s results and conclusions are as follows:(1)According to the results of the model under two scenarios, the farmland and construction land in the future experience an increasing trend, forestland, water and unused land all show a trend of decrease, there was no obvious change on the grassland. But the land area change of water transfer scenario is much smaller than no water transfer.(2) In all systems, water system is the biggest ecological water requirement in all kinds of systems, followed by farmland system and forest land system, the three systems are the main types of ecological water requirement. The quantities of the water system ecological water requirement will determine the ecological water requirement quantitiesofthe whole river basin.(3)Compared to two scenarios, under the no water transfer scenario, the whole river basin ecological water requirement increase slowly with the passage of time, that the future ecological water requirement for river basin is growing; underwater transfer scenario, ecological water requirement significantly reduced over time in the future. That is after the implementation of The South to North Water Transfer Project, river basin ecological water requirement will be greatly reduced. |
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