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As a natural reserve relatively resilient to climate variability, groundwater has provided large benefits to irrigated agriculture in semi-arid OECD countries. It has supported the development and expanded production of commodity crops in the US Midwest and Mexico and high value products in semi-arid areas of Mediterranean Europe or the Middle East. But intensive use beyond recharge capacity in certain regions has depleted resources and increasingly generates significant negative environmental externalities, including stream depletion, saline intrusion and land subsidence.
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Groundwater resources sustain a significant and increasing share of irrigated agricultural production. On a global scale, groundwater represents over 40% of consumptive irrigation water use, covering just under 40% of irrigated land globally. In OECD countries, groundwater for agriculture irrigation is used on 23 million hectares, for an estimated annual volume of 123.5 km3, accounting for about 20% of global irrigation withdrawals.
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This chapter presents the challenges of groundwater management, and provides an overview of the status and use of groundwater for agriculture in OECD countries. It examines recent data, trends, and indicators of groundwater use and stress at the national, regional and aquifer levels, and reviews the evidence on the expected effects of climate change.
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This chapter discusses the diversity of agricultural groundwater systems in OECD countries with the goal of identifying the main factors that may need to be accounted for when managing groundwater systems. Acknowledging these characteristics, the key challenges associated with agricultural groundwater pumping in OECD countries are reviewed, considering, in particular, reversible and irreversible externalities.
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This chapter provides a normative analysis of agricultural groundwater management policies. Through an economic lens, it reviews the rationale for groundwater public policies and management, and discusses the advantages and drawbacks of the main instruments used to manage groundwater in agriculture.
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This chapter reviews policies and management approaches for agricultural groundwater management in OECD countries. Responses to a questionnaire are used to examine the diversity of national and regional policy instruments. An analysis is also conducted at the regional level to assess whether the choice of management instruments can be linked to specific characteristics and constraints of agricultural groundwater systems.
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This chapter combines lessons from Chapter 3 and from past policy successes and failures to identify a package of recommendations for sustainable groundwater management. It then evaluates whether OECD policies fit this framework and concludes on the need for improvements in the context of the expected growing importance of groundwater management for agriculture under climate change.