Global Water Use

Schmied, Hannes Müller; Flörke, Martina; Döll, Petra

doi:10.1007/978-3-030-38948-2_29-1

Cited by 2 publications

(1 citation statement)

References 45 publications

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“…Groundwater is a crucial source of water supply for humanity, accounting for one‐quarter of total freshwater abstractions worldwide in 2017, and even more than one‐third of the abstractions for domestic use (IGRAC, 2018; Müller Schmied et al., 2023). Groundwater abstractions lead to a decline in the groundwater table and a decrease in groundwater discharge to streams (de Graaf et al., 2019), the latter causing reduced seasonal low flows (Wittenberg, 2015).…”

Section: Introductionmentioning

confidence: 99%

Global‐Scale Groundwater Recharge Modeling Is Improved by Tuning Against Ground‐Based Estimates for Karst and Non‐Karst Areas

Wan,

Döll,

Müller Schmied

2024

Water Resources Research

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Quantification of groundwater recharge is highly important for understanding freshwater systems and sustainable management of both groundwater and surface water bodies, but it is very uncertain. To improve the global‐scale simulation of diffuse groundwater recharge (GWR), we developed, for the first time in global hydrological modeling, an approach for explicitly simulating GWR in karst areas, based on the World Karst Aquifer Map and ground‐based estimates of karst GWR. Ground‐based estimates of both karst and non‐karst GWR from 5,600 locations were aggregated to produce estimates for 816 globally distributed 0.5° grid cells, including 64 representing karst GWR. Applying WaterGAP2.2e, we found that karst GWR is best approximated by total runoff from land (without soil overflow and urban runoff). The GWR algorithm for non‐karst GWR was tuned against ground‐based estimates for 422 non‐karst grid cells outside of Australia. While simulated GWR tends to underestimate GWR in non‐karst areas with mean annual ground‐based GWR > 200 mm/yr, it overestimates national GWR in six out of seven European countries. With an increase in the coefficient for the discharge from groundwater to surface water bodies, the updated GWR algorithm results in an improved fit of simulated streamflow to observations, including low flows. Global mean annual GWR and thus renewable groundwater resources (without Greenland and Antarctica) are estimated to be about one‐half of the total renewable water resources, or 21,000 km3/yr, which is over 50% higher than the standard model estimate. 20% of global GWR is generated in karst areas, which cover about 11% of the world's land surface.

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Section: Introductionmentioning

confidence: 99%

Global‐Scale Groundwater Recharge Modeling Is Improved by Tuning Against Ground‐Based Estimates for Karst and Non‐Karst Areas

Wan,

Döll,

Müller Schmied

2024

Water Resources Research

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Groundwater stress in Europe—assessing uncertainties in future groundwater discharge alterations due to water abstractions and climate change

Söller,

Luetkemeier,

Müller Schmied

et al. 2024

Front. Water

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Groundwater sustains human well-being and ecosystems functioning. Many regions in Europe have experienced declining groundwater levels caused by decreasing groundwater recharge (GWR) or increasing groundwater abstractions (GWAs). These changes can lead to groundwater-related stress, threatening ecosystems and water supplies. Existing groundwater stress indicators estimate stress during a given period but do not address how stress changes or show the uncertainty of future stress. We propose a novel indicator of future groundwater stress (GWSI) due to changes in GWR and GWA and, thus, the alteration of long-term mean annual groundwater discharge (GWD). Groundwater stress is defined as any alteration in GWD since ecosystems are adapted to an equilibrium state. Focusing on decreasing GWD, which is generally more harmful than increasing GWD, we quantified the future GWSI in Europe by integrating scenarios of GWR and GWA in 2070–2099. GWR was evaluated using an ISIMIP2b multi-model ensemble of eight global hydrological models driven by the output of four global climate models under two greenhouse gas emission scenarios. GWA scenarios for irrigation, domestic and manufacturing sectors were combined with the GWR projections to generate an ensemble of GWSIs, simplified into three groundwater stress scenarios (high, intermediate, low). Projected GWSIs vary significantly among the scenarios. For the high-stress scenario, 58% of Europe’s land area is projected to experience a GWD decrease of at least 25% under RCP8.5 compared to 38% under RCP2.6, while the respective values are 26 and 1% for the intermediate-stress scenario. Groundwater demand management alone might not prevent GWD declines under the high-stress and intermediate scenarios, particularly under RCP8.5. Therefore, climate change mitigation might imperative for reducing the decline of GWD, especially in Eastern and Southeastern Europe, where changes in GWR are projected to be the primary cause of declining GWD (in the high abstraction scenario under RCP8.5). Under RCP2.6, reductions in GWAs by 25–75% might balance a GWD decline in parts of Spain and Italy where GWAs are high, even in the high-stress scenario. In line with the precautionary principle, we recommend adapting to the high-stress scenario to minimize harm to the beneficiaries of groundwater.

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Global Water Use

Cited by 2 publications

References 45 publications

Global‐Scale Groundwater Recharge Modeling Is Improved by Tuning Against Ground‐Based Estimates for Karst and Non‐Karst Areas

Global‐Scale Groundwater Recharge Modeling Is Improved by Tuning Against Ground‐Based Estimates for Karst and Non‐Karst Areas

Groundwater stress in Europe—assessing uncertainties in future groundwater discharge alterations due to water abstractions and climate change

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