水资源约束缓解与区域经济增长——来自“南水北调”工程的经验证据

Water Constraint Mitigation and Regional Economic Growth:Evidence from the South-to-north Water Diversion Project

党的二十大报告强调,在关系安全发展的领域加快补齐短板,提升战略性资源供应保障能力。水资源短缺是制约中国华北地区经济高质量发展的最大刚性约束,南水北调东、中线工程旨在从根本上缓解华北地区城市缺水问题。本文通过构建适用于中国发展实际的水资源约束理论模型,阐述南水北调工程促进受水区经济发展和城市扩张的内在机理。在此基础上,基于2009~2020年南水北调中线工程受水省份(京津冀豫)县级层面的夜间灯光亮度数据、土地覆盖数据、地下水位监测井数据、企业注册数据和土地出让数据,采用双重差分模型,实证分析南水北调中线工程对受水省内受水县经济增长和城市扩张的影响,并进一步探究其实现机制。结果发现:南水北调中线工程通水促使受水县经济发展水平显著提升了6.1%,并使受水县建成区面积占比显著提升了0.671个百分点;上述结论经一系列稳健性检验后依然成立。该项工程建成通水缓解了受水县的水资源约束,使受水县地下水位增长率显著提高了1.329个百分点,且异质性分析发现受水县地下水位上升越多,其建成区扩张越快。机制分析表明,该项工程建成通水显著提升了受水县的招商引资能力和人口吸引力,所产生的人口集聚效应将为当地经济发展提供长期人力资本保障。

Water constraint is the biggest rigid constraint of economic and social development,and water shortage is a common threat faced by the world.The Yellow River Basin is the birthplace of Chinese civilization,with a long history of development,high development intensity,high population density,and severe soil erosion.In the 1980s,the per capita water resources of the Yellow River Basin were 320 cubic meters,which was one-eighth of the national average for the same period.Therefore,the shortage of water resources seriously restricts the economic development of the Yellow River Basin.To alleviate this problem,after nearly half a century of selection and demonstration,China began construction of the world’s largest water conservancy project(the South-to-North Water Diversion Project(SNWTP))in 2002.The east and middle routes of the SNWTP were completed and opened in 2013 and 2014,respectively.As of January 2022,the cumulative volume of water transferred by the SNWTP reached 5.288 and 44.712 billion cubic meters,respectively,significantly alleviating the severe water shortage problems in the recipient areas.This study aims to assess the effect of the middle routes of the SNWTP(SNWTP-MR)in promoting economic development and urban expansion in the recipient counties by alleviating its water resource constraints.This study initially stems from China’s institutional context of“economy scaled fundamentally determined by its total water resources,”incorporating the Leontief form of production input into the Douglas production function,thereby constructing a theoretical model for water resource constraints that are congruent with the actual conditions of water resource utilization and urban development in China.Subsequently,this study empirically evaluates the impact of the SNWTP on economic development and urban expansion in the recipient provinces(Beijing,Tianjin,Hebei,and Henan)using a difference-in-differences model.The evaluation is based on county-level night-time light data,land cover data,groundwater level monitoring data,business registration data,and land concession data from 2009 to 2020.Lastly,we examine the mechanisms through which the alleviation of water resource constraints promotes economic development and urban expansion through the lens of capital and business influx into water-receiving regions,as well as shifts in their aggregate population and demographic composition.The results reveal that 1)the completion of SNWTP-MR significantly contributed to a 6.10 percentage point increase in the level of economic development in the recipient counties and a significant 0.671 percentage point increase in the built-up area share of the recipient counties;the above findings still hold after a series of robustness tests.2)The completion of the project eased the water resource constraint of the recipient counties and significantly increased the groundwater level growth rate of the recipient counties by 1.329 percentage points,and the heterogeneity analysis reveals that the more the groundwater level rises in the counties,the faster the built-up area expands.3)The mechanism analysis reveals that the completion and opening of the project significantly improved the investment attraction capacity and population attractiveness of the recipient counties,and the resulting population agglomeration effect will provide a long-term human capital guarantee for local economic development.This study has important policy implications for a comprehensive assessment of the economic benefits of major cross-regional water conservation projects.The SNWTP-MR has contributed to a 6.1%increase in economic development in the recipient counties,promoting economic growth in the northern regions and slowing down the widening economic gap between the north and the south.For example,Henan Province,the province that receives an enormous amount of water allocated from the SNWTP-MR,ranks fifth in the country with a population increase of 5,342,000 from 2010 to 2020,and its capital city,Zhengzhou,ranks first in central China in terms of the total population in 2020,surpassing Wuhan.Benefiting from the“southern water,”Zhengzhou has built several artificial lakes,creating business districts and university cities based on artificial lakes,which has dramatically improved the city’s competitiveness.However,this study only explores the economic benefits of the SNWTP-MR,so its ecological and environmental benefits need to be further studied.