Global Water Use and Its Changing Patterns: Insights from OECD Countries

Water resources are an important foundation for sustainable socioeconomic development. Revealing water use efficiency, the change in water use trends, and their driving mechanisms is essential for facilitating the scientific and reasonable prediction of water demand, thereby guiding the scientific planning and management of water resources. This study utilizes socioeconomic and water usage data from 65 countries spanning the years 1970 to 2020, employing the panel smooth transfer regression (PSTR) model to analyze the relationship between per capita total water withdrawal and per capita GDP. Additionally, Random Forest (RF) methods and empirical statistical analyses are implemented to identify the driving factors, control variables, and critical thresholds of water use trends in countries with different levels of development. The results show that: (1) there exists a nonlinear relationship between per capita total water withdrawal and per capita GDP on a global scale, with 70% of the countries exhibiting an inverted U-type trend in water usage; (2) the observed decline in per capita total water withdrawal in relation to per capita GDP is primarily driven by technological advancements and the optimization and enhancement of production structure; (3) common characteristics of OECD (Organization for Economic Cooperation and Development) countries that have reached their peak water usage include a service sector contribution to GDP exceeding 60%, urbanization levels at 70%, and per capita GDP surpassing USD 20,000. The observed changes in water use trends and the characteristic indicators associated with peak water usage, under conditions devoid of engineering interventions and resources constraints, can serve as valuable references for medium- and long-term water resources planning and water demand management in developing nations.