| Against the background of climate change, water and carbon balance between human-being system and ecosystem has become the primary environmental problem. On one hand, climate changes affect multi-feedback mechanism of multi-processes which are associated with water cycle severely, and intensify the contradiction between water supply and demand. It also intensifies the occupation of ecological water and land, reducing carbon-capture capacity of ecosystem. On the other hand, the amount of fossil fuel demand increases carbon emission. These two aspects have comprehensively increased net carbon emission. Although techniques of carbon-emission reduction and measures of carbon-capture enhance are implemented and it has shown a "carbon reduction and capture increase trend", perfect condition with the minus of net carbon emission has not come out. That is because the two above measures are separated. Based on the relationship between carbon emission and socio-economic water use and the relationship of carbon capture and water demand of ecosystem, the rational allocation of water resource towards low-carbon development mode relates the carbon emission processes to water resource system. It reasonably decreases the socio-economic water use through water saving measures. Furthermore, through the joint allocation of water resources and net carbon emission, it curbs the carbon emission and guarantees a better water supply for the ecosystem, which therefore strengthens the carbon capture capacity. It will be a new method to renovate traditional exploit and utilization of water resources and mitigate and adapt to climatic change.Based on the "natural-artificial" water cycle and carbon cycle, regional carbon-water coupling mechanism is identified and then, connotation, overall task, basic characteristics, target and principles are proposed in this research. Supported by the above theories, carbon-water coupling system is generalized and its network is drafted. It makes use of carbon-water model and prototype observation to identify carbon-water coupling mechanism quantitatively and predict water demand and carbon emission in the future. Allocation schemes at different planning years are set up and are simulated by rational allocation model of water resources towards low-carbon mode, results of which are analyzed. Finally, suggested scheme and guarantee measures are obtained. The research gains innovation on theory and technology.It expands the theory of rational allocation of water resources. Compared to the traditional one, rational allocation of water resources is based on regional carbon-water coupling mechanism with major lines of "nature-artificial" water cycle and carbon cycle, which couples carbon cycle with water resources system, and focuses on relationship between social-economic water use and carbon emission and the relationship of eco-environment water use and carbon capture. It expands research category of traditional mode. The overall target not only considers water deficit in the traditional model, but also considers net carbon emission. Meanwhile, low carbon is regarded as the basic principles. Rational allocation of water resources towards low carbon mode guarantees social-economic development. The point is that it has the ability of inhibiting carbon source and increasing the guarantee degree of eco-environmental water. The theory above is supported by two key technologies on identification of regional carbon-water coupling mechanism and rational allocation of water resources towards low carbon development mode.Identifying technique of regional carbon-water coupling mechanism divides each simulation unit into social-economic and eco-environmental system through constructing the generalized carbon-water coupling system. Artificial water cycle and processes of carbon emission are simulated in the former system while natural water cycle and processes of carbon capture in the latter one. Combining the comprehensive advantages of field prototype observation, geographical information technology and numerical simulation, spatial and temporal evolution of carbon-water cycle are deserved with carbon-water coupling model. Efficiencies of carbon emission, carbon capture and net carbon emission per cubic meters of water are emphasized. It can directly reflect relationship between carbon cycle and water cycle in the social-economic and eco-environmental system, so as to overcome the disadvantage of previous studies without consideration of social-economic system and problem on separate analysis of carbon "source" and carbon "sink"Allocation model is the key of rational allocation of water resources towards low-carbon mode. This model not only takes net carbon emission into the target function, but also regards carbon balance, carbon-water index and carbon-emission index of hydraulic projects as the confined conditions. The solution method of multiple-objective programming based on ideal point and genetic algorithm is used for solution in the model. With the premise of steady economic growth rate, schemes set implements measures of saving water and water-transferring projects to meet water demand especially for eco-environment in the future. Meanwhile, it proposes guarantee measures from aspects of productive structure, water saving, water supply mode and hydraulic engineering arrangement.Guided by the basic theory and technical framework, the research is applied in the Baiyangdian basin. Results are shown as follows:(1) Identifying carbon-water coupling mechanism in Baiyangdian basin Carbon cycle and water cycle are simulated by regional carbon-water coupling model, whose results are relatively great. Evolution and relationship of them are quantitatively identified. Detailed results show that amount of carbon emission and net carbon emission were both in the increasing trend during2005-2010when carbon capture changed slightly and the whole region being carbon source; precipitation could not meet the demand of evapotranspiration during1997-2010;although amounts of water supply and demand were both in the trend of decrease, it’s of deficit in the basin without considering instream flow and ecological water demand of wetland. What’s more, efficiencies of carbon emission and net carbon emission per cubic meter water were in the increasing trend but the efficiency of carbon capture was not variable.(2) Forecast of carbon emission and water demand for Baiyangdian basinAfter identifying evolution of factors in the future such as population, urbanization level, economic growth rate, GDP, industrial structure and energy consumption, all kinds of energy consumption are calculated and then total carbon emission is deserved with carbon-emission indexes. Meanwhile, water demand for production, domestic living and ecoenvironment are got according to water quota which is from plans and standards or extrapolated by historical series. Results show that compared with low-carbon mode, amounts of carbon emission in the extensional-development mode will increase by19.3Mt,64.1Mt and319.1Mt in the planning year of2015,2020and2030respectively and total amount of water demand in the basin are1.27billion m3,1.53billion m3and21.6billion m3without consideration of water demand for instream flow and wetland ecosystem.(3) Recommended schemes of Baiyangdian basin at different planning level yearsCompared with the present status, water deficit and net carbon emission are decreased by42.72%and63.02%respectively in the recommended scheme of2010. However, water deficit is10.88%, meaning water supply at present can’t meet the requirement. It requires water supply from other basin. At the same time, amount of groundwater exploitation is not reduced and capacity of carbon capture is not enhanced. Compared with the extensional-development mode, water deficit and net carbon emission could be decreased by26.1%and81%respectively in the recommended scheme of2015, in which amounts of water supply and water demand could be both4.185billion m3and water deficit is zero. However, the whole basin also is a carbon source. In the planning year of2020, if economic growth rate and energy consumption are according with the extensional-development scheme, it’s necessary to implement high water-saving mode, in which water deficient and amounts of carbon emission and net one could be reduced by30.7%,11.9%and13.5%respectively while amount of carbon capture could be increased by3.7%. If economic growth rate and energy consumption are according with the low-carbon-development mode, medium water-saving scheme could be fine, in which water deficit and amounts of carbon emission and net one could be reduced by30.7%,60.1%and74.9%respectively and amount of carbon capture could be increased by4.3%. In the planning year of2030, with the background of low-carbon economic development mode, water deficit and amounts of net carbon emission could be reduced by40.3%and112.6%compared with the extensional-development mode. The whole basin could be a carbon sink.Research on application in Baiyangdian can directly support plans of water resources and eco-environment, groundwater supply, diversion projects including South-to-North and Yellow River Diversion. This research is of great practical significance. |
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