Groundwater plays a major, if often unrecognized, role in both hydrologic and human systems. The majority of the world's drinking water probably comes from groundwater, and in the last half century, there has been an amazing, if largely ignored, boom in agricultural groundwater use that has provided improved livelihoods and food security to billions of farmers and consumers. However, increased use of groundwater has also created problems, and there are fears—sometimes challenged—that the boom may soon turn to bust. This article reviews the recent literature on the geographic and temporal dimensions of groundwater use and the range of technological and institutional approaches that have been applied in attempts at its management. It then examines the key reasons the resource has proven so difficult to manage and concludes that, in many cases, the most promising solutions may lie outside the groundwater sector and within a broader approach to resource systems.

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Global Groundwater? Issues and Solutions

Assessment of exploitable groundwater resources of Denmark by use of ensemble resource indicators and a numerical groundwater–surface water model

Groundwater overdraft occurs when extraction exceeds both natural and induced aquifer recharge over long periods. While ultimately unsustainable and invariably having detrimental effects, overdrafting aquifers is common and may be temporarily beneficial within a long-term water management strategy. Once a region chooses to end overdrafting, water management must change if increased water scarcity is to be avoided. Integrated water-management models allow aquifers and overdraft to be analyzed as part of a regional water-supply system. Incorporating economics into the model establishes a framework for evaluating the costs and effects of groundwater management actions on the entire system. This economic-engineering approach is applied in a case study of the Tulare Basin in California, USA, where previous economic studies showed optimal pumping depths have been reached. A hydro-economic optimization model is used to study the economic effects and water management actions that accompany ending overdraft. Results show that when overdraft is prohibited, groundwater banking using conjunctive-use infrastructure built between 1990 and 2005 largely annuls the cost of not overdrafting. The integrated economic-engineering approach quantifies effects of groundwater policies on complex regional water-resource systems and suggests promising strategies for reducing the economic costs of ending aquifer overexploitation.

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Ending groundwater overdraft in hydrologic-economic systems

This paper examines the relevance to groundwater management of Ostrom’s design principles for managing common property resources. Experience in four case studies of groundwater management in the Murray Darling Basin in Australia and the Upper Guadiana Basin in Spain suggests that while Ostrom’s design principles are relevant, sustainable groundwater management depends on the effective collaboration between government authorities and water users. A flexible and adaptive management approach is required, with collaboration between scientists, policy makers, water suppliers, and water users. Key management challenges include agreeing on a sustainable level of extraction, and establishing effective coordination and collaboration, and monitoring and control systems. Further case studies of groundwater management and their synthesis could make a useful contribution to the transition towards sustainable groundwater management regimes.

The challenge of groundwater governance: case studies from Spain and Australia

The semiarid Mancha Occidental aquifer represents a paradigmatic case of intensive groundwater use for agriculture. Irrigation has proven a catalyst for welfare in the area over the last three decades, if at a significant environmental cost and while raising concerns as to its mid-term sustainability. This paper describes an interdisciplinary exercise of scenario design and modelling, providing a methodology to couple hard-science numerical modelling approaches with the involvement of key water actors. Given the long-standing conflicts in the area, modelling work largely focuses on carrying out a vulnerability assessment rather than on trying to find solutions. The system's most resilient aspects and its drivers for change are identified, while their potential implications for aquifer sustainability are assessed under the light of the mandatory objectives established by the European Union Water Framework Directive for all Member States. Whereas modelling results imply that such objectives are unlikely to be met, a vulnerability assessment suggests that even adverse scenario pumping patterns could be sustained in the mid- to long-term (two to four decades).

Vulnerability assessment of groundwater resources: A modelling-based approach to the Mancha Occidental aquifer, Spain

Water resources sustainability hinges on interrelated physical, chemical, biological, and human processes, all of which may affect the quantity and quality of available water supplies California's decades-long transition process from intensive and often unmanaged groundwater development toward more effective, sustainable integrated water resources management has resulted in important lessons The process offers insights to other countries that seek to achieve sustainability Long-term systematic groundwater and surface water monitoring programs and ongoing assessment of regional groundwater systems are an integral part of management On local to global scales, the need for fundamental data, regional resources assessments, and increased support for scientific and technological advances is becoming increasingly apparent The scientific community must enhance society's understanding of the essential links between basic data needs and the advancement and application of scientific approaches for effective water management Correspondingly, scientific and political communities must coordinate common interests in endeavors toward sustainable management Public outreach is a necessary complement to achieve sustainability goals and garner support for the programs needed to develop water policies based on sound science, manage water resources, and meet future water demands while avoiding unacceptable impacts

T. N. Narasimhan

Papers

California's evolution toward integrated regional water management: a long-term view