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Taylor R.,University College London | Longuevergne L.,University of Texas at Austin | Harding R.,UK Center for Ecology and Hydrology | Todd M.,University of Sussex | And 8 more authors.
IAHS-AISH Publication | Year: 2010

As the world's largest accessible store of freshwater, groundwater plays a critical role in enabling communities to adapt to freshwater shortages derived from low or variable precipitation and high freshwater demand. As highlighted by the IPCC in 2001 (TAR) and 2007 (AR4), our knowledge of how groundwater systems respond to changes in climate and abstraction remains severely limited. Although new diagnostic tools such as the global aquifer map (WHYMAP) and satellite monitoring of changes in total water storage under the Gravity Recovery and Climate Experiment (GRACE) have recently been developed, their deployment is greatly constrained by a dearth of reliable and sustained observations of groundwater systems. Land-surface models (LSMs) embedded in general circulation models and offline macro-scale hydrological models continue to employ simplistic characterisations of groundwater systems due, in part, to the absence of global or continental-scale data sets to test or tune these models. Structural modelling challenges, such as the long response times of some groundwater systems to hydrological change and substantial uncertainty in projections of precipitation and evapotranspiration, persist. New insight regarding the relationship between global hydrological change and groundwater systems, including the impacts of intensive abstraction for irrigation on groundwater storage and changing rainfall intensity on groundwater recharge, have recently been developed from basin-scale studies where reliable groundwater observations exist. These studies provide a compelling case for the expansion of groundwater monitoring networks and compilation of a global groundwater archive (IGRAC), comparable to that for other components of the hydrological system (e.g. WMO, GRDC, WGMS), to improve understanding and management of the groundwater system under global hydrological change. Copyright © 2010 IAHS Press. Source


Wada Y.,University Utrecht | Heinrich L.,International Groundwater Resources Assessment Center
Environmental Research Letters | Year: 2013

Internationally shared, or transboundary, aquifers (TBAs) have long played an important role in sustaining drinking water supply and food production, supporting livelihoods of millions of people worldwide. Rapidly growing populations and their food demands cast significant doubt on the sustainability of TBAs. Here, this study provides a first quantitative assessment of TBAs worldwide with an aquifer stress indicator over the period 1960-2010 using groundwater abstraction, groundwater recharge, and groundwater contribution to environment flow. The results reveal that 8% of TBAs worldwide are currently stressed due to human overexploitation. Over these TBAs the rate of groundwater pumping increased substantially during the past fifty years, which worsened the aquifer stress condition. In addition, many TBAs over Europe, Asia and Africa are not currently stressed, but their aquifer stress has been increasing at an alarming rate (>100%) for the past fifty years, due to the increasing reliance on groundwater abstraction for food production. Groundwater depletion is substantial over several TBAs including the India River Plain (India, Pakistan), the Paleogene and Cretaceous aquifers (the Arabian Peninsula), and a few TBAs over the USA-Mexico border. Improving irrigation efficiency can reduce the amount of groundwater depletion over some TBAs, but it likely aggravates groundwater depletion over TBAs where conjunctive use of surface water and groundwater is prevalent. © 2013 IOP Publishing Ltd. Source


Conti K.I.,University of Amsterdam | Conti K.I.,International Groundwater Resources Assessment Center | Gupta J.,University of Amsterdam | Gupta J.,UNESCO-IHE Institute for Water Education
Current Opinion in Environmental Sustainability | Year: 2014

Threats to groundwater sustainability demand governance. However, groundwater governance regimes are developing incongruously across geographic levels. Therefore, this research raises the question, how does lack of consensus regarding principles of groundwater law manifest itself as legal pluralism at different geographic levels? Current literature is reviewed and norms for groundwater governance are presented at each geographic level along with American, European, Asian and African examples. This is a new exploration of legal pluralism and its consequences for groundwater access, allocation and sustainability. It shows that challenges regarding scope, jurisdiction and application of norms manifest themselves in legal-plural regimes with differing consequences: groundwater degradation and problems of access and allocation on the one hand and improved, coherent governance structures on the other. © 2014 Elsevier B.V. Source


Wada Y.,University Utrecht | Van Beek L.P.H.,University Utrecht | Van Kempen C.M.,International Groundwater Resources Assessment Center | Reckman J.W.T.M.,International Groundwater Resources Assessment Center | And 3 more authors.
Geophysical Research Letters | Year: 2010

In regions with frequent water stress and large aquifer systems groundwater is often used as an additional water source. If groundwater abstraction exceeds the natural groundwater recharge for extensive areas and long times, overexploitation or persistent groundwater depletion occurs. Here we provide a global overview of groundwater depletion (here defined as abstraction in excess of recharge) by assessing groundwater recharge with a global hydrological model and subtracting estimates of groundwater abstraction. Restricting our analysis to sub-humid to arid areas we estimate the total global groundwater depletion to have increased from 126 (32) km3 a-1 in 1960 to 283 (40) km3 a-1 in 2000. The latter equals 39 (10)% of the global yearly groundwater abstraction, 2 (0.6)% of the global yearly groundwater recharge, 0.8 (0.1)% of the global yearly continental runoff and 0.4 (0.06)% of the global yearly evaporation, contributing a considerable amount of 0.8 (0.1) mm a-1 to current sea-level rise. © 2010 by the American Geophysical Union. Source

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