Spatiotemporal variation and long-range correlation of groundwater depth in the Northeast China Plain and North China Plain from 2000∼2019

Northeast China Plain (NECP) and North China Plain (NCP). Groundwater resources in the northern plains of China are the primary source of domestic and irrigation water, and long-term overexploitation may cause groundwater depletion and deterioration in these plains. In this study, based on observations of groundwater depth (i.e., the depth of phreatic water below the land surface) from 2000 to 2019 in the NECP and NCP, the spatial distribution characteristics and long-range correlation (LRC) of the regional groundwater depth are analyzed using the geostatistical method and fractal theory. In terms of the spatial distribution of groundwater depth, an overall trend of decline and then recovery from 2000 to 2019 can be observed in the NECP, indicating that the persistent decline of groundwater depth is not conspicuous, while there is a persistent decline of groundwater depth in the NCP. Regarding the LRC of groundwater depth, the Hurst exponents calculated using the R/S analysis demonstrate the persistence of groundwater depth variation in the NECP and positive persistence of groundwater depth decline in the NCP. The Hurst exponent reveals that the groundwater depth in the NECP will likely remain stable in the future, while the groundwater depth in most areas of the NCP may continue to decline if the dominant factors remain unchanged. Moreover, the dynamic change in the groundwater depth of the NECP may be mainly affected by natural structural factors, while anthropogenic factors may trigger that response in the NCP.