| Under the influence of global climate change and increasingly human activities,the process of regional water cycle is undergoing the dualistic evolution of"nature-society",and how to maintain the healthy state of the water cycle has become an important proposition to maintain the sustainable development of human society.Various approaches have been proposed for maintaining the health status of water cycles so that they can fulfill their ecological and economic roles.This paper firstly analyzes the connotation of healthy water cycle and puts forward the health assessment model of regional water cycle,then explores the calculation method of ecological water demand based on land use,and finally makes a safety diagnosis of water supply and demand in Beijing,Tianjin and Hebei Province.The main contents and conclusions are as follows:(1)The healthy water cycle mode should first ensure the normalization of water ecological function and water function,ensure the ecological value of natural water circulation.Secondly,it's necessary to form an efficient water resource utilization mode and give full play to the human services value of water resources.Based on this,this paper constructs the evaluation index system of health water cycle index from 17 dimensions in 4 dimensions,and demarcates the health threshold of corresponding index according to the water resources background condition in the evaluation area.And the combination methods of the Composite-index and the Fuzzy Recognition assessment were adopted to evaluate the health condition of water cycle.The average health point of water cycle in Beijing,Tianjin and Hebei Province was 3.33,which was generally in a sub-healthy state,but there was a significant difference in the health status of water cycle among the regions.The result of dimension evaluation shows that water resources utilization(3.61)>water ecological level(3.56)>water resources quality(3.29)>water resources abundance(2.38)and fuzzy evaluation also got the same evaluation results.Although the efficiency of water resources utilization is already relatively satisfactory,the shortage of water resources is still the major obstacle to a healthy water cycle in the Beijing-Tianjin-Hebei region.(2)The calculation method of ecological environment water demand based on land use category could reduce the data requirement effectively when calculating the ecological environment water demand for the overall area,and can predict the ecological water demand and its distribution characteristics easily and quickly in cities,grasslands,woodlands,lakes,wetlands and rivers as well.For the entire Beijing-Tianj in-Hebei region,its ecological water requirement has remained at around 12 billion m3 for a long time,reaching 44%of the total water resources in the region.However,the current annual ecological water consumption is only 1.677 billion m3,which is still far from water demand.Therefore,Beijing-Tianjin-Hebei region still needs to ensure constant water replenishment before it can further restore and enhance its water ecological level.(3)The output of water resources allocation model shows that when agricultural water quota and per capita domestic water quota increase from 80 to 110m3/mu and 50 to 100m3,respectively,the regional water shortage shows a stepwise increase up to a maximum of 8.074 billion m3.The water supplement of South-to-North Water Diversion can meet the water demand of Beijing and Tianjin.As for Hebei Province,when the agricultural and domestic water quota are maintained at 110m3/mu and 70m3,the amount of additional water could make the local water resources reach the balance of supply and demand.Seeking regional cooperation among all prefecture-level cities in Beijing,Tianjin and Hebei,promoting the transfer of population and industry and giving full play to the potential of inter-basin water transfer will be the effective way for sustainable development in the regions. |
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