What policies to manage groundwater use in agriculture? Lessons from a study of OECD countries.
Groundwater is increasingly used to support agricultural irrigation. In OECD countries, groundwater irrigation covers 23 million hectares of cropland in key agricultural production regions. There, it serves as a reliable water source for irrigation, providing water on demand, while being largely unaffected by short term hydrological variations. In many regions, however, the expansion of such irrigation has led to groundwater overdraft, in some cases with significant negative economic and environmental impact. Managing these externalities is a critical challenge for irrigated agriculture in these regions. Past experience show that policies have a role to play, but that the design and combination of approaches matters critically to ensure sustainable outcomes. The presentation draws on a 2015 study that studied a wide range of national and subnational management instruments in over twenty OECD countries with very different agriculture and hydrogeological contexts. A wide diversity of policies applied to manage groundwater use in agriculture. Policies are founded on different legal systems; they focus on the demand side, supply side or both, and use direct or indirect approaches to regulatory, economic or collective management. While there is no visible link between the scope of management and the intensity of constraints, economic and supply-side approaches are more prevalent in areas under higher agricultural groundwater stress. These policies are then compared with a grid of necessary conditions for successful groundwater management, relying in particular on a tripod combination of regulatory, economic and collective-action approaches to cope with intensive groundwater use. Survey results indicate that these recommendations have not been uniformly applied in OECD countries or regions that use groundwater intensively for agriculture. In particular, there seems to be a relatively low level of knowledge on groundwater resources and use. Most OECD countries or regions in the survey sample have also applied incomplete management schemes, missing part of the recommended approaches.