Shifts in trends and correlation of water scarcity and productivity over China

Increasing water productivity has been viewed as an important strategy for reducing regional water scarcity in many countries, including China. However, some studies argue that improving water productivity may lead to a rebound effect that reversely aggravates water scarcity. This contradictory relationship is because that previous empirical assessments mostly focus on limited time spans, which raises a theoretical hypothesis that their correlation would presumably shift over long-term period under different development stages. Thus, this study performed a comprehensive analysis over China based on multiple survey-based datasets and revealed the shifts in water scarcity and productivity in terms of their trends and correlation during 1979 - 2020. Results showed significant turning points of water scarcity from upward to downward trends across China in the early 21 st century, except in southwestern China where water scarcity continuously intensified. Water productivity showed a widespread accelerating trend because of large increase in nonagricultural water productivity. Furthermore, the correlation between water scarcity and productivity was positive in the early stage of China ' s development pathway when both of them were low but simultaneously increasing for more profit. Then, their positive correlation shifted to negative in response to the necessity for water scarcity alleviation, and increasing water productivity would be effective to reduce water scarcity with the complement of water-related policies that prevent its rebound effect. The results broadened our knowledge on the long-term evolution of regional water scarcity, and highlighted the changing relationship between water scarcity and productivity that was essential for guiding water policy making.