Human-induced global groundwater decline simulated by H08-GMv1.0

Decline in groundwater levels has induced severe socio-economic consequences globally. These include water scarcity, land subsidence, and salinization of arable land. However, the capability of current Global Water Models (GWMs), including H08, to simulate groundwater level declines is still limited, partly because the groundwater, especially the lateral flow processes, used to be downplayed. A recent effort has been made to enable explicit representation of groundwater level and lateral flows in H08. The newly developed model is named as H08-GMv1.0 but has previously only been validated in terms of steady-state simulation. Here, we present the monthly transient simulation results from H08-GMv1.0 during 1979-2019, validated by ~20,000 USGS monitoring wells. The Theil-Sen trend of global groundwater level demonstrates severe decline in major aquifer systems worldwide. The results also show that in several irrigation intensive systems, i.e., High Plains aquifer, Indus River Basin aquifer, and Northern China Plain, the human groundwater pumping is the main cause for groundwater level declines, which calls for urgent and coordinated groundwater governance and demand-side management interventions.