Fig. 1: Spatial-temporal patterns of China’s groundwater quality and affected population.

Distributions of PGQ probability in China in 1980 (a), 2000 (b), and 2020 (c); Population in regions with PGQ probability greater than 0.5 in 1980 (d), 2000 (e), and 2020 (f). Map Source: Standard Map Service of the Ministry of Natural Resources, People’s Republic of China [Map Review Number: GS(2019)1822].