Synergy Effects And Risk Analysis Of Water-energy Nexus In Shenzhen Based On System Dynamics And Copula Function

Water and energy are the two key elements necessary to keep a city running.In the context of rapid economic development,rising population and global climate change,the demand for the two kinds of resources is increasing day by day.To ease pressure on the water-energy nexus,the World Bank launched a global initiative entitled"quantifying the trade-offs between water and energy";in 2014,the United Nations World Water Assessment Programme chose"water and energy"as the theme of world water day.Some studies show that by 2030,the global water supply shortage rate will reach 40%,and the global energy demand will increase by 36%compared with 2010,which will aggravate the contradiction between the supply and demand of water and energy resources.The use of water and the consumption of energy are highly intertwined in urban economic activities.For example,some researchers found that the energy consumption of the whole water cycle in China accounted for 19.45%of the total electricity consumption.However,in the past,the management and policy making of water and energy resources were often carried out separately,and the close relationship between them was neglected.Shenzhen is a typical resource-constrained megacity in China.The rapid economic development has deepened the challenges of water resources and energy.A deep understanding of the water-energy nexus is critical to achieving sustainable resource management.At first,this paper sorts out the current state of water and energy use in Shenzhen,using partial least squares method to extract the driving factors of the increasing demand.Besides,the water-energy system dynamics model is constructed,and three different policy scenarios including benchmark scenario,constraint scenario and collaborative management scenario are set for simulation analysis.Finally,copulas function is introduced,with the help of Matlab programming for the risk analysis of water-energy system.The main results of this paper are as follows:(1)the supply of water and energy resources in Shenzhen is highly dependent on importing from other regions,so the increasing demand intensifies the contradiction between supply and demand,which demonstrates the classical water-energy nexus.Population size,economic development level,water supply and energy supply structure,as well as the use efficiency have a great role in the growth of demand.(2)the projected energy demand range of Shenzhen during the study period is[35.16,59.97]million tons,and the projected water demand range is[16.41,35.42]×10~8 m~3.The collaborative management scenario oriented by water-energy nexus can relieve the pressure of water and energy system of Shenzhen to the greatest extent,and achieve the total quantity control target.Therefore,it is recommended that the water resources system and energy system departments should strengthen cooperation and formulate policies for collaborative management of water and energy resources.(3)based on the Copula function theory,the risk analysis of the water-energy nexus system is carried out,and different risk probability distributions are obtained.For example,at the level of comprehensive risk of 0.826,the risk of water resources system is 0.92 and that of energy system is 0.88.Correspondingly,the water demand should be controlled within 3.403 billion m~3 and the energy consumption should be controlled within 57.33 million tons.Through this research,it is hoped that the obtained conclusions can provide reference for policy making and resource management.