| Cities are regions where water resources and fossil energy are consumed intensively.Rapid urbanization led to population growth and economic agglomeration,which resulted in substantial increase in water and energy consumption and carbon emission.It caused huge pressure on carbon emission reduction,but also restricted sustainable development of economic and society seriously.In the urban system of economic and social,water,energy and carbon were correlative and interwoven closely,forming a coupling system.The coupling coordination degree of system was a direct embodiment of urban resource utilization and production efficiency,but also reflected the environmental impact of urban economic and social activities.Therefore,internal mechanism,matching pattern and coupling coordination degree of urban water-energy-carbon(WEC)coupling system were revealed,and influence and evolution trend of rapid urbanization on WEC coupling system were analyzed in this paper.It was helpful to reveal resource coupling pattern and its relationship with carbon emission and to deepen theory research on multi-factor coupling relation at city scale.It could also provide practice guidance for the selection of urbanization development mode with multiple goals of water energy conservation and carbon emission reduction.Water and energy consumption and carbon emission in Zhengzhou was researched based on mechanism analysis of urbanization to WEC coupling system through multi-source data,such as remote sensing night light data,land use raster data and statistical data.From the perspective of land use,spatial-temporal characteristics of water and energy consumption and carbon emission intensity were analyzed taking an example as Zhengzhou.Combination pattern and matching relation of WEC in different land use types were discussed and the impact of rapid urbanization on WEC system was analyzed.Based on the system dynamics model,WEC coupling system was simulated and carbon emission potential was analyzed contrastively under different scenarios.Finally,some policy suggestions were put forward for water-energy conservation and carbon emission reduction at city scale.The main conclusions are as follows:(1)The total amount and intensity of water and energy consumption showed an increasing trend,but spatial-temporal characteristics of water and energy consumption and carbon emission intensity in different land use types were obviously different in Zhengzhou.Water consumption reached 19.35×10~8 m~3 in 2020 and urban construction land consumed most water resource,which was 64.66%of total water consumption.Energy consumption reached 5940×10~4 tce in 2020.The energy consumption urban construction land,rural land and transportation land accounted for 87-96%of total energy consumption,while agricultural land accounted for only 4-13%of total energy consumption.Carbon emission showed an upward trend rapidly from 2000 to 2020 in Zhengzhou.Urban construction land emitted more carbon than other land use types,which accounted for 68.82%of Zhengzhou(2020)because urban construction land carried more production activities and energy consumption.Carbon emission showed the distribution characteristics of high in the east and low in the west and agglomeration in central towns from the perspective of spatial pattern.(2)There were large differences in the combination characteristics and matching relationships of WEC in different land use types.In general,combination characteristics of WEC were closely related to land use type.The land carrying high water consumption and low energy consumption activities mainly showed a combination pattern of high-low-low(such as cultivated land).Moreover,the land carrying high water consumption and high energy consumption activities mainly showed a combination pattern of high-high-high(such as urban construction land).In addition,the combination pattern of WEC intensity showed low-low-low model in agricultural land and high-high-high model in construction land(except for transportation land).Their combined feature characteristic was high-high or low-low model when two elements were matched closely,while combined feature characteristic of two elements were high-low or low-high model when their feature matching degree is low.(3)The coupling coordination degree of WEC system showed an upward trend in Zhengzhou.It indicated that urban utilization efficiency of water and energy consumption has been improved significantly and positive result has been achieved in carbon emission reduction.There was a clear correlation between WEC that correlation coefficients of water-energy,water-carbon and energy-carbon were 0.75,0.87 and 0.95,respectively.It indicated that coupling degree of WEC system was high,while the coordination degree of WEC system was poor due to the difference in the growth rate of water and energy consumption and carbon emission.The growth rate of water and energy consumption and carbon emission has slowed down and coupling and coordination degree of system has been optimized in the process of rapid urbanization.Zhengzhou was at a high-quality coordination in 2020 that the coupling degree of WEC system reached 0.9975,the coordination degree reached 0.8427 and the coupling coordination degree reached 0.9169.(4)Rapid urbanization was an important factor to affect coupling coordination degree of the WEC system.In particular,the transformation of land use type changed water and energy consumption intensity,which determined the coupling coordination degree of WEC system.The degree of urbanization has been improved continuously,which reached 80.60%in 2020in Zhengzhou.There was an obvious correlation between the degree of urbanization and coupling coordination degree of WEC system(R~2=0.97).It showed that rapid urbanization was an important factor affecting the coupling coordination degree of WEC system.Changes in population,GDP,water and energy consumption and carbon emission intensity affected coupling coordination degree of WEC system directly.In addition,the transformation of land use type changed water and energy consumption intensity,which determined the efficiency of urban resource utilization and the degree of carbon emission.In particular,the process of transforming agricultural land to construction land led to the growth of water and energy consumption and carbon emission,but also affected the coupling coordination degree of WEC system by changing the WEC combination pattern and matching relationship.(5)Simulation results showed that the impact of land urbanization on urban WEC coupling system is greater than that of economic urbanization and population urbanization.The comprehensive scenario was more conducive to the realization of optimization goal of WEC coupling system,which based on multi-objectives of water-saving and energy-saving and carbon reduction.Water and energy consumption and carbon emission under different urbanization scenarios showed a sustained increase.The change rate of water and energy consumption and carbon emission under land urbanization increased slower than those under economic urbanization and population urbanization.Carbon emission will reach 7106.28×10~4t under the baseline scenario in 2035.Carbon emission will reach 7097.98×10~4 t,4969.19×10~4 t,5915.90×10~4 t respectively under water-saving scenario,energy-saving scenario and carbon reduction scenario.Compared with the baseline scenario,water and energy consumption and carbon emission were reduced by 30.37%,35.76%and 44.52%under the comprehensive scenario(2035),and peak time of water and energy consumption and carbon emission was 23.00×10~8 m~3,7801.46×10~4 tce,4177.04×10~4 t in 2034,2031 and2029,respectively.(6)Based on the above conclusions,the following suggestions for future urban development were put forward:(1)To design planning for coordinated development and utilization of resources from the perspective of WEC coupling.(2)Optimizing the process of water and energy consumption at city scale to promote resources efficient use.(3)Building a coordinated and optimized development system of water,energy and carbon to guide low-carbon development.(4)Improving the urban carbon emission evaluation system to achieve resource conservation and carbon reduction targets. |
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