Easier Said than Done: Will evolving groundwater rules in the West support markets?

• Author: Ayres, Andrew B.
• Position: NATURAL RESOURCES

In America's western states, groundwater--water stored in underground aquifers--is a key source of supply for cities, farms, and other users. Groundwater often accounts for 50% or more of annual water supply in states such as Arizona, California, New Mexico, and Texas. Much of this is used for agricultural irrigation, but it is common for municipal and industrial users to rely heavily on groundwater for their supplies. In arid and drought-prone regions, intermittent wet periods result in aquifer recharge that supports increased extraction during dry times. Without this natural storage, modern life in the American West would not be feasible.

Despite this importance, groundwater often is not governed by precise allocation rules. Claims to the subterranean resource are seldom quantified, extraction typically is not measured, and it generally is not quite clear who owns what. In many cases, aquifer depletion has resulted. Beyond overdrafting a common resource, pumping groundwater can impose additional meaningful external costs on others, such as by causing land to subside (or sink), which reduces storage space and can damage infrastructure, or compromising water quality by drawing seawater into the aquifer in coastal regions. For example, subsidence in California's San Joaquin Valley has caused canal sections in some major water infrastructure projects to sink, reducing their conveyance capacity by 50% or more. It can also affect surface water users who divert water from rivers and lakes: when these sources are sufficiently interconnected with groundwater, pumping can reduce streamflow. Responsibility for addressing those effects is often not clear.

A changing climate will complicate matters. More variable snowpack that melts more quickly may lead to earlier, less manageable runoff, and ultimately less recharge unless efforts are made to capture flood flows. More persistent and intense droughts may likewise increase the demand for water stored underground. At the same time, the population of the West is growing and, along with it, new demands for reliable water access.

The consequences of prolonged overdraft, intensified by recent droughts, have stoked increased interest in improving and further formalizing groundwater management in some western states. Although established management regimes surround Arizona's urbanized areas of Phoenix and Tucson, drawdown of groundwater in rural areas has intensified in recent years--alongside calls for more active management and state legislative efforts to give users the tools to implement it. Farther east in Texas, the "rule of capture" is still a dominant force, and strict production controls on groundwater extraction have historically been more the exception than the rule. Local efforts to control access and implement robust metering have increased in recent years but are still few. In California, users in a number of basins have succeeded in constituting comprehensive groundwater pumping rules, some defining quantified and tradable rights to pump. A 2014 California law, the Sustainable Groundwater Management Act (SGMA), may drive similar solutions in other overdrafted basins.

NEW LEGISLATION FORESEES LOCAL SOLUTIONS IN CALIFORNIA

SGMA mandates the formation of local agencies that will address long-term basin overdraft. These Groundwater Sustainability Agencies (GSAs) must design institutions, plans, and implementation strategies through collaborative processes with local stakeholders. Successful implementation will involve balancing the basin over the long term so that total extractions do not exceed recharge. The law requires that pumpers avoid other harmful impacts (e.g., subsidence) that are "significant and unreasonable." Defining what constitutes such an impact is a key task for the GSAs.

But this will not occur overnight. Although the initial Groundwater Sustainability Plans (GSPs) have been submitted for the state's critically overdrafted basins, the GSAs need not secure sustainable management until 2040. Many other basins in the state will be submitting their plans this coming year, with an attainment deadline of 2042. In the meantime, the GSPs will be reviewed by state...