Evaluation And Scenario Analysis Of Water Environment Carrying Capacity

With the acceleration of urbanization,industrialization,and rapid economic development,problems such as water resource depletion,water environmental pollution,and water ecological destruction have become increasingly serious.They threat the healthy living of the residents and the sustainable development of the region.As an important city of "the belt and road" and "the Yangtze River economic zone",how to achieve water conservation and pollutant emission reduction while ensuring rapid economic development is the key task for NanjingTaking Nanjing as an example,the research on water environment carrying capacity(WECC)was carried out.Firstly,the status of WECC in Nanjing from 2006 to 2016 was evaluated and graded.Secondly,the systematic dynamics model was constructed to simulate the WECC before 2030,and the main obstacle factors were also explored.Thirdly,six development scenarios were designed to predict WECC in Nanjing during the planning period.Finally,some suggestions were put forward on promoting the regional WECC.Accordingly,some theoretical bases and technical supports should be provided for the sustainable development of Nanjing.The main results were shown as follows(1)The evaluation indicator system of WECC was constructed,which conforms to the characteristics of regional socio-economic and environment.The grading standards of single indicator were also determined.These provided the basis for the subsequent evaluation of WECC.According to the results of genetic projection pursuit,the evaluation index of WECC in Nanjing from 2006-2016 was 0.5285-2.2740,which increased from "low" to "medium" level.Socio-economic subsystem and water environment subsystem developed better,but the level of water resources subsystem was low.(2)A system dynamics model suitable for Nanjing was established to simulate WECC.The results showed that during the planning period of 2017-2030,GDP,population and waste water discharge increased,and the gap between water supply and demand expanded.WECC showed a slow upward trend in this period,and only 2030 reached the "high" level.And the level of water resources subsystem was still low.The calculation results of obstacle degree showed that the main obstacle factors affecting WECC in Nanjing in the future were:population density>per capita domestic sewage discharge>per unit area wastewater discharge>water supply-demand ratio>per capita comprehensive water consumption.(3)Six scenarios for the development of Nanjing before 2030 were designed,including no policy preference,high population growth,high economic growth,water conservation,water pollution control and comprehensive development schemes.Based on this,the change of regional WECC under different policy measures was studied.From the comparison of different scenarios,the order of promoting WECC is:comprehensive development scheme>water saving scheme>pollution control scheme>high economic growth scheme>no policy preference scheme>high population growth scheme.If Nanjing City adopts moderate population growth,rapid economic development,strong water conservation and pollution control measures,the WECC will increase rapidly.Accordingly,suggestions for the improvement of WECC in Nanjing City are proposed.