A global-scale two-layer transient groundwater model: Development and application to groundwater depletion. (April 2017)

• Record Type: Journal Article
• Authors: de Graaf, Inge E.M.; van Beek, Rens L.P.H.; Gleeson, Tom; Moosdorf, Nils; Schmitz, Oliver; Sutanudjaja, Edwin H.; Bierkens, Marc F.P.
• Is Part Of: Advances in water resources. Volume 102(2017)
• Page Start: 53
• Page End: 67
• Publication Date: 2017-04
• Subjects: Hydrology -- Periodicals; Hydrodynamics -- Periodicals; Hydraulic engineering -- Periodicals; 551.48
• DOI: 10.1016/j.advwatres.2017.01.011
• Languages: English
• ISSNs: 0309-1708

Abstract

Highlights: Development of a global-scale groundwater model, simulating lateral groundwater flows and including information on the vertical structure of aquifers. Groundwater head fluctuations and groundwater storage changes are simulated at the global-scale. Hotspot regions of groundwater depletion are identified. Abstract: Groundwater is the world's largest accessible source of freshwater to satisfy human water needs. Moreover, groundwater buffers variable precipitation rates over time, thereby effectively sustaining river flows in times of droughts and evaporation in areas with shallow water tables. In this study, building on previous work, we simulate groundwater head fluctuations and groundwater storage changes in both confined and unconfined aquifer systems using a global-scale high-resolution (5′) groundwater model by deriving new estimates of the distribution and thickness of confining layers. Inclusion of confined aquifer systems (estimated 6–20% of the total aquifer area) improves estimates of timing and amplitude of groundwater head fluctuations and changes groundwater flow paths and groundwater-surface water interaction rates. Groundwater flow paths within confining layers are shorter than paths in the underlying aquifer, while flows within the confined aquifer can get disconnected from the local drainage system due to the low conductivity of the confining layer. Lateral groundwater flows between basins are significant in the model, especially for areas with (partially) confined aquifers were long flow paths crossing catchment boundaries are simulated, thereby supporting water budgets of neighboring catchments or aquifer systems. The developed two-layer transient groundwater model is used to identify hot-spots of groundwater depletion. Global groundwater depletion is estimated as 7013 km 3 (137 km 3 y − 1 ) over 1960–2010, which is consistent with estimates of previous studies.