River Water Environment Resilience Assessment And Sustainable Utilization

Maintaining a healthy river water environment is the urgent needs of watershed management in China.However,the river water environment in China is still faced serious challenges because of the problems of hard pollution control,short water resource supply,human activities.The question about how to maintain and recover the health of rivers and give full play to the service functions of the river has become the focus of river water environmental management research.Tthe mechanism of scientific evaluation of river water environmental resilience is discussedbased on the theory of alternative stable states.Scheafer model,a model usually for renewable resources management,is applied in water environment.This research provides technical support and the scientific guidance for river water pollution control,water environmental restoration,and sustainable utilization.The South to North Water Diversion Project has great impact on the downstream.After literature review on the alternative stable states theory,using this project as an example,this research gives the definition of resilience,elements,characteristics,and influencing factors of river water environmental system resilence.It combines the variable fuzzy recognition model with the improved AHP,formulates a computable water environment restorability model with an application to the middle-low reach of Hanjiang River.Based on the study of the water environment capacity of the typical area and the total amount of pollutants in the study area,the sustainable utilization of the water environment in the middle and lower reaches of the Hanjiang River was analyzed.The novel work and conclusions are summarized below:(1)The resilience of river water environment system is deduced by using the alternative stable states transformation mechanism.Definitions and influencing factors of water environment resilience and mechanism are described.(2)Impact study of the South to North Water Transfer Project on hydrological conditions in the middle and lower reaches of Hanjiang river using both Mann-Kendall method and RVA.Mann-Kendall method was used to analyze and test the hydrological sequences of typical sites(Huangjiagang,Huangzhuang and Xiantao)from 1990 to 2015.The results show that mutation occurs for all three sites near the years of 2003 and 2014.The RVArange method was then used to evaluate the impact of water transfer project on the middle and lower reaches of the Hanjiang River.The results indicate overall change degrees of all locations exceed 70%.(3)The population,economy,waste water discharge,and pollutant discharge in the middle and lower reaches of the Hanjiang River were investigated inthe base year 2010.Forecasts were given for total waste water,pollutant discharge and total pollutant discharge to rivers in 2020,2030 and 2040.Water environment capacity of the Hanjiang River were analyzed using the mid-point model and the uniform model for three cases,with or without compensation project of the Yangtze River to Hanjiang.The results show that the South-to-North Water Diversion Project reduces the runoff and flow rate.At 95%,90%,75%assure rates,water environment capacity of CODMn decreased by 12.86%,15.5%and 17.49%,respectively,that of NH3-N decreased by 14.55%,13.5%,37.3%,respectively.(4)The allowable waste discharges were computed for different years in the future based on the idea of total pollutant control.The resource development model of water environment system was established using Scheafer model.The ideal discharge rate for different level years was analyzed.The results show that the development and utilization of the water environment in the middle and lower reaches of the Hanjiang River before 2030 is reasonable and is moderately utilized.A new equilibrium state may be establishedafter 2030.(5)Based on the theory of water environment resilience,the influencing factors of water environment resilience was analyzed from the aspects of water resources utilization,pollution capacity and pollution level,river ecology,social economy,environmental management and management level.The variable fuzzy recognition model with the modified AHP was utilized in evaluating water environment resilience?The spatial and temporal variability of water environment resilience in Xiangyang section and Xiantao section of middle and lower reaches of Hanjiang River were evaluated.The results show that water environment resilience of Xiangyang section and Xiantao section increased from 2001 to 2010.The change at Xiantao section is larger than that of Xiangyang section.The spatial distribution of water environment resilience was studied in 2010.It shows that the resilience of water environment in Xiangyang,Zhongxiang,Xiantao and Caidian was at the level of Grade ?,and the resilience of water environment in Qianjiang,Tianmen and Xiaoguan was at grade ?in 2010.Overall,this work presents new methods in assessment of water environment resilience and pollution control using the alternative stable states theory.These methods can be further applied to the utilization and protection of water environment of the Han River.