Assessment Of Water Supply Security And Risk In Northwest Inland Arid Area Under Changing Environment

Under the dual influence of climate change and human activities,water security,especially water supply security,in the arid inland areas of northwest my country has increasingly become one of the core components of national security.It is urgent to study its water supply security and risks at the national strategic level.Traditional water supply security is usually considered from small scales(such as cities)at the level of water sources,water transmission and distribution projects,water quality control,and water supply prices.Less consideration is given to water supply security issues at the basin or regional scale.It is urgent to carry out research on the theoretical method and technical framework of regional water supply security assessment on a large regional scale.The arid inland areas of the northwest are in short supply of water resources and the ecological environment is fragile.With the advancement of market economy and globalization,a large number of agricultural products with high water consumption have been exported for a long time,which increasingly tests and even threatens the water security of the arid inland areas of the northwest.Based on theoretical methods such as system theory,resource and environmental carrying capacity theory,complexity theory,and the "nature-society-trade" water cycle model in the northwest inland region.This study analyzes and studies the theoretical framework of water supply security in the arid inland region of Northwest China,such as the connotation characteristics,system structure,and evolution drivers.From the three aspects of water resources supply side,demand side and water resources management,determine the three criterion layers of the risk of bearing factors,the vulnerability of the bearing body and the system prevention ability,and construct the theoretical framework,model technology and index system of water supply safety evaluation in the arid inland area of Northwest China.Taking the Tarim River Basin,whose land area and water resources account for more than half of my country’s inland arid regions,as an example,comprehensive consideration is given to the availability of water under changing environments,the demand for water resources in the basin driven by strategies,and the virtual water flow under market mechanisms.The core elements are to carry out water supply safety and risk assessment in the Tarim River Basin under the changing environment.The main research results are as follows:(1)On the basis of ensuring the healthy development of the ecology,the regional water supply security aims to ensure the sustainable water use of the regional social economy,strengthen the management of water demand,improve the efficiency of water use,and adopt engineering and non-engineering measures to ensure the water quality and quantity requirements of the sustainable development of the region.Under the changing environment,the water supply safety system in the arid inland area of Northwest China is composed of a water source subsystem,a water supply engineering subsystem,a user subsystem and a virtual water subsystem.The system has the characteristics of integrity and synthesis,spatial heterogeneity,dynamics and randomness,adaptability and self-regulation,long-term and irreversibility,openness and complexity.Climate change affects water supply security from the formation of runoff and intra-year changes.Human activities put forward higher requirements for water supply from the perspective of demand.Long-term large-scale virtual water output will exacerbate the gap between supply and demand and increase the pressure on water supply.Based on the three main perspectives of water resources supply side,demand side and water resources management,the water supply security evaluation framework in the arid inland area of Northwest China is constructed from the three criteria of bearing factor risk,bearing body vulnerability and system prevention ability.From 8 sub-criteria layers,including water resources development and utilization,virtual water flow,water pollution degree,water resource endowment,water use vulnerability,water conservancy project support capacity,water saving capacity,and wastewater treatment,23 indicators are selected to constitute the water supply security evaluation index system.Considering the forecast demand for future water supply security assessment,this study adopts the fuzzy comprehensive evaluation method to conduct water supply security assessment.(2)Water availability is a central part of water supply security.Water availability is a central part of water supply security.Conventional methods face a series of difficulties in carrying out large-scale regional-scale water resource forecasting under the condition of climate change.This study proposes a regional water resource prediction model that combines climate model output with SVR.The model has good performance and high simulation accuracy,and can be applied to river basins or regions to predict future water resources.Using this model,it is expected that the self-produced water resources in the Tarim River Basin will remain between 36 and 38 billion m~3 in 2030 and 2050,which is basically the same as the average water resources of 36.9 billion m~3 in 1956 and 2000,but lower than 2000～The average amount of water resources in 2018 was 41 billion m~3.Taking into account the ecological water consumption demand(14 billion m~3～16 billion m~3),the annual average inflow water(6.87 billion m~3),the water consumption of artificial rivers and unconventional water resources considering the evolution of oasis in the basin and vegetation evaporation.Under different climate models,the economic and social water resources available in the basin will be about 34.8-37.1 billion m~3 in 2030,and about 34.7-35.1 billion m~3 in 2050.(3)Based on the fact that the socio-economic development of the basin in the past 20 years,especially the failure of irrigation scale regulation and control,and the judgment of the future development trend of the basin.Low,medium and high agricultural water demand scenarios are set up with the current statistical area,the current remote sensing interpretation area,and the per capita standardized area as the core,and the water demand scenarios for the socio-economic development of the basin in 2030 and 2050 are predicted.The results show that under the low,medium and high scenarios,the water demand of the basin will be about 27.94 billion m~3,36.76 billion m~3,and 37.87 billion m~3 by 2030,and 25.31 billion m~3,32.91 billion m~3,and 37.115 billion m~3 by 2050,respectively.(4)The flow of virtual water within or between regions has become an important factor affecting the security of water supply in the arid inland areas of Northwest China.Using the input-output model,the analysis of the virtual water transfer between industries and regions in the Tarim River Basin shows that:The sectors in which virtual water is transferred out of the industry are mainly agriculture,which are mainly transferred to four industries:construction products,textiles,and other services.In 2018,the current situation of net agricultural water transfer in the industry was 6.938 billion m~3 and 8.601 billion m~3 based on statistical area and remote sensing interpretation area,respectively.The low,medium and high scenarios in 2030 are 6.427 billion m~3,8.856 billion m~3,and 9.117 billion m~3,respectively,and the low,medium and high scenarios in 2050 are 6.085 billion m~3,8.289 billion m~3,and 9.397 billion m~3,respectively.The current situation of net water transfer in the Tarim River Basin between regions was 11.590 billion m~3 and 13.764 billion m~3 respectively based on statistical area and remote sensing interpretation area in 2018.The low,medium and high scenarios in 2030 are 9.702 billion m~3,13.042 billion m~3 and 13.311 billion m~3 respectively.The low,medium and high scenarios in 2050 are 8.322 billion m~3,10.996 billion m~3 and 12.537 billion m~3 respectively.(5)Based on the status quo,water supply security and risk analysis in 2030 and 2050,the Tarim River Basin low scheme is basically safe and above,and the water supply risk is low,while the medium and high schemes are insecure in 2018 and basically safe in 2030 and 2050.And there are significant differences across states.Applying the rebound effect model,it is found that the rebound effect of agricultural water consumption is 166%,showing a "tempering phenomenon",which is an important potential threat to water supply security.Based on water supply safety and risk assessment,this paper puts forward countermeasures and suggestions on water resources protection,economical and intensive utilization,and water supply management on the basis of conventional water source conservation,joint water and soil adjustment,structural adjustment,and water supply engineering guarantee.