There is a great deal of scientific evidence documenting groundwater overuse throughout the world. Despite this evidence, the resources of many, if not most, aquifers are not managed sustainably. This presentation discusses aquifers around the world, identifies factors that have driven management success, and considers whether these factors can be used to identify other aquifers likely to achieve similar results. Surveyed aquifers that are succesfully managed or have taken important steps towards management include the West Coast Basin in California, the Eastern Snake Plain Aquifer in Idaho, and the Genevese Aquifer in France and Switzerland. They are contrasted with overused aquifers, including the San Joaquin Basin in California, the Ogallala Aquifer in the Midwestern United States, and the Sana'a Aquifer in Yemen.
Where groundwater management is working, the following factors have been integral to success: (1) an imminent, certain and broad threat of long-term damage to the water supply, (2) the presence of urban water users, (3) a source of supplemental water, and (4) the presence of junior water rights holders. These factors, briefly described below, will be presented with explanations and examples from the surveyed aquifers.
First, managed aquifers have faced imminent and certain threats that impact many users such as seawater intrusion. In contrast, declining groundwater levels alone often fail to drive management implementation, at least in part because groundwater users find the evidence insufficiently certain to support management decisions.
Second, groundwater management is often funded by urban water users. Urban water users have long-term interests in sustainable local supplies. They are responsible to the public and thus subject to significant political pressure, and they can pass the cost on to many rate payers.
Third, the availability of supplemental water facilitates groundwater management by limiting the burden on pumpers. Where an aquifer is in overdraft, some combination of reduced pumping and increased recharge is required. Although supplemental water is more expensive, without it pumping reductions will have a bigger economic impact and may be too severe for water users to withstand.
Finally, junior water rights holders are often the first to support groundwater management because they risk losing their pumping rights and thus will compromise in exchange for more certain groundwater allocations. In contrast, senior water rights holders are more likely to advocate for the status quo through reliance on their superior legal claims and the belief that they can exclude others from the aquifer before being compelled to reduce their own use.
Implementing effective groundwater management, from the initial engagement of water users to the funding and establishment of management institutions, is a very difficult process in any basin, but the challenges are greater in some basins than others. I have seen this in my three decades of water law practice. Because of the number of aquifers already under great stress, it will not be possible to succesfully implement management in all of them simultaneously. Understanding the drivers of successful groundwater management helps identify aquifers with high probability of success and informs management efforts.