Evaluation On Sustainability Of The Water Resources Utilization In Tibet Based On Eco-economic System Approach

With the rapid development of social economy and the intensification of human activities,water demands in many countries and regions are increasing,and the utilization of water resources gradually exceeds the environmental carrying capacity.Although the total amount of water resources in Tibet Autonomous Region is rich,its environment is fragile.The increasing social and economic water use process has lowered ecological water requirement,resulting in groundwater overexploitation,water pollution,soil erosion and other environmental problems,which restricts the sustained and rapid development of Tibet’s economy.Therefore,it is the realistic need of the current development of Tibet to keep the water resources utilization within the limit of environmental carrying capacity,and to realize the sustainable utilization of water resources.Most scholars use the multi-attribute evaluation method to study the sustainability of water resources utilization.However,there are many problems,e.g.the large amount of data is difficult to collect,the index information is overlapping,and the multi-attribute correlation cannot be accurately described.Water resources system is a complex system involving economic,ecological and other factors,including interdisciplinary subjects such as hydrology,systematics,ecology,economics and sustainable development theory.It is of great significance for sustainable utilization of water resources in Tibet to explore the interrelation and evolution of flow,energy,and information in the water resources system from overall perspective.Based on the eco-economic system approach,combined with the current situation of water resources utilization in Tibet,the present study uses emergy analysis,ecological footprint analysis,and ecological network analysis to evaluate the sustainability of water resources utilization from the aspects of hydropower generation,total amount of regional water resources,natural-social binary water cycle,and water use in socio-economic sectors.This thesis also analyzes the complex impacts on water resources utilization in Tibet,and forecasts the changes of socio-economic water resources system of Tibet in 2022 based on scenario analysis,which provides theoretical and methodological support for the sustainability evaluation of water resources utilization in Tibet.The main methodologies and conclusions of this thesis are as follows:（1）Based on the emergy theory,this thesis evaluates the sustainability of Pangduo hydropower station in Tibet,compares the emergy-based indices of Pangduo with other hydropower projects,and analyzes the impacts of ecosystem service losses and social disruption on the system sustainability.The results show that:a)The total energy input of Pangduo hydropower station in 2016 was 4.99×10²⁰ sej/a,in which the ecosystem service loss was the largest energy input.The total emergy output was 8.28×10²⁰ sej/a,in which the hydropower generation was the largest emergy output.b)The total ecosystem service losses of Pangduo hydropower station were 1.49×10²⁰ sej/a,among which wastes,sediments,and biodiversity loss were the three largest ecosystem service losses,accounting for 57.0%,12.5%,and 10.5%of their totals,respectively.c)The emergy-based indices evaluation results showed that the Pangduo hydropower station was lower sustainable than other hydropower stations in China and abroad,which was mainly due to the calculation differences.The ecosystem service losses have great impacts on the sustainability evaluation results of Pangduo hydropower station.（2）This study uses the ecological footprint method to calculate the water resources ecological footprint and water resources ecological carrying capacity in Tibet during2011～2016 and the sustainability of water resources utilization in Tibet is evaluated.The results show that the per capita water resources ecological footprint of Tibet decreased from 1.7173 hm² in 2011 to 1.5946 hm² in 2016,and the water use efficiency was low.The total amount of water resources in Tibet is rich and is significantly affected by precipitation.The water resources ecological carrying capacity was higher than that of in other provinces in China and the world.The water resources consumption in Tibet was less than carrying capacity,so the potential of water resources development is huge.The ten thousand yuan GDP of water resources ecological footprint decreased,indicating the water use efficiency in Tibet was gradually increasing,but the calculated results of ecological coordination coefficient of water resources showed that the coordination between economic development and water resources utilization was poor.（3）According to the natural-social binary water cycle of the Lhasa River Basin,the water use system of the Lhasa River Basin is established based on the ecological network analysis.The ecological use of water is considered in the network model construction.The relationships between network nodes were determined,the changes of network structure from 2000 to 2016 were analyzed,and the sustainability of water resources utilization was evaluated.The results show that:a)The positive utilities were greater than the negative utilities,but the coordination degree of was decreasing from2006 to 2016.Exploitation（control）,mutual,and competitive relationships accounted for 44.4%,27.8%,and 27.8%of the total ecological relationships,respectively.b)The total system throughput in the Lhasa River Basin was decreased,which affected by the total amount of water resources.Flow diversity and average mutual information showed the increase-decreased trends.Development capacity,ascendency,and overhead presented similar trends.The degree of order shows a downward trend,and the system robustness shows an upward trend.The possible reason is that more network pathways are needed to improve the network efficiency of the water use system.（4）Based on the input-output analysis and the ecological network analysis,the water resources input-output table of Tibet in 2012 was calculated,and a seven-node socio-economic water resources system in Tibet was constructed.Network stability analysis reflects the system robustness through the tradeoffs of network efficiency and redundancy.The results showed that the network redundancy was higher than efficiency.Throughflow analysis calculates the total throughflow and quantifies the direct and indirect flows in the system.The results showed that direct flows were larger than indirect flows.Network control analysis explores the control and dependence intensity of the network nodes.The results showed that the agriculture sector and the power supply sector were the biggest controller and dependent of the socio-economic water resources system,respectively.Network utility analysis evaluates the complex relationships among sectors.The results showed that the system was mutual and synergistic in overall,exploitation（control）relationships were dominant,while the competitive relationships accounted for a small proportion.Because the competitive relationship is not conducive to system development,it is necessary to reduce the competitive relationship and improve the water use efficiency for system sustainability.（5）To analyze the influencing factors of water resources utilization in Tibet and predict the future development of the socio-economic water resources system,this study compiles the input-output table of Tibet in 2017 based on the water resources input-output table of Tibet in 2012 and the statistical data in 2017,analyzes the influencing factors of water resources utilization in Tibet by structural decomposition analysis,and the changes of ecological relationships and system robustness among different sectors of water resources system of Tibet in 2022 are simulated.The results showed that:a)The changes of direct water use coefficients and Leontief inverse matrices contribute most to the decrease of water resources utilization in Tibet,while the change of final demand increases the water resources utilization.b)The socio-economic water resources system of Tibet in 2022 will be synergistic under different scenarios,and the ecological relationships among different sectors will not be changed significantly.In the case of decreasing direct water use coefficient and final demand of agriculture sector,the network efficiency and the robustness are improved.