Application of the gleization soil layer to assess centurial drops in shallow groundwater levels across the southeastern coast of China

Groundwater is a critical resource for global sustainable development, but it is often poorly monitored and managed. The gleization soil layer is the Critical Zone between the pedosphere and underground hydrosphere. It records the groundwater table fluctuation for an extended period, providing an ideal opportunity to evaluate shallow groundwater level dynamics. The present work applies the gleization soil layer to explore centurial changes and the complex interactions of factors affecting (climate, parent material, economic development, and land use) in shallow groundwater levels across the southeastern coast of China using GIS and regression analysis, based on 249 soil profiles collected from 2010 to 2012. The results showed approximately 60% drops in shallow groundwater level over a century, and deep groundwater level mostly appeared in north plain and coastal delta regions. Climate dominates the changes in groundwater level for the long term (34.0%). Still, the development of the economic belts mitigated its influences and played a more important role (26.1%) than climate (20.8%) on current. Land use and parent material also contributed to shallow groundwater level dynamics. The shallow groundwater level change across different land uses was more likely to occur in a subtropical climate and Delta with Sediments and Alluvial deposits. We concluded that the Huanghuai plain and Yangtze River Delta's shallow groundwater level dynamics would slow down due to the regulation of water conservancy facilities and groundwater protection policies. However, shallow groundwater level in Pearl River Delta would decline continuously due to the emerging economy and urbanization. Overall, this work is the first to investigate the coastal centurial drop in shallow groundwater level through the gleization soil layer. It provides a possible approach for filling in gaps in groundwater level data and highlights the different contributions of climate and economic growth to the groundwater level over time.