Briefing Report: The Ground Rules on Groundwater

Thursday, June 3, 2010

Groundwater is a vast and vital resource for local agricultural and urban economies throughout California. As policymakers grapple with the question of how to stretch diminishing supplies to meet the state's needs, groundwater is increasingly under the microscope as a management tool to enhance storage and operational flexibility.

But there are limits to the state's authority over groundwater use. In California, the right to use groundwater is a property right, and state-level regulation of groundwater use would represent a major infringement on that right. Furthermore, the management or permitting of each groundwater basin statewide would be a monumental task, as the characteristics of each basin are both highly unique and extraordinarily complex. It would also be needless since many basins are either in no distress or have some level of local management.

While there is a state interest in improving groundwater management, policymakers should be aware of both the practical limits of statewide management, the limits of the state's authority to do so, and the extent to which local efforts are already underway to help solve the supply and demand imbalance.


Groundwater is a major component of California's water use. Somewhere between 40% and 50% of Californians rely to some extent on groundwater supplies. The Department of Water Resources (DWR) estimates an average of 15 million acre-feet of groundwater is used each year, about 35% of statewide water use in an average year and about 40% in dry years. In regions with limited access to surface water those numbers are much higher: over 80% of water use in the Central Coast region comes from groundwater, and about 70% of water use in the southern Sierra. Of the 515 identified groundwater basins and subbasins statewide, just 116 of them account for 95% of public supply wells, 99% of municipal pumping, and 90% of agricultural pumping.

Groundwater depletion is not a new issue. In fact, the story of early 20 th Century water development in parts of California involves groundwater basins being tapped dry. While the development of surface water helped stem the tide of groundwater depletion, it is still a significant problem. On a statewide basis, DWR estimates an annual "overdraft" -- the condition where groundwater use exceeds its recharge -- of about one to two million acre-feet (MAF) statewide. According to the US Geological Survey, in the San Joaquin Valley alone the long-term overdraft is estimated at about 60 MAF. That's roughly 1.5 years worth of statewide water use. Groundwater tables in the valley have fallen up as much as 400 feet in some places, though in others groundwater is still readily accessible just below the surface.

It is easy to see how and why overdraft can occur. In basins with no management controls, property owners' access to groundwater is limited only by what they can put to reasonable and beneficial use on the overlying land. There is little incentive for the individual user to limit his use for the sake of the overall basin condition or to take action to replenish the basin, since that user will see only a modest percentage of the benefits of those actions. Thus this "tragedy of the commons" often requires some mutual action to protect the groundwater rights of each property owner.

The most common results of groundwater depletion are increased pumping costs and reduced water quality. In the post-war Southern California boom, the depletion of groundwater levels drew seawater into those basins making them unusable. Overdraft can also cause compaction of sediment overlying the basin, a condition known as subsidence. In one infamous case, an area on the west side of the San Joaquin Valley has dropped over 30 feet in elevation in the last century due to heavy groundwater pumping.

Overdraft also has impacts beyond the basin itself. In most areas, groundwater and surface water are hydraulically connected, meaning that dry ground above a depleted basin will naturally absorb more surface water. Thus the overdraft of groundwater has an impact on rights to surface water, which are also property rights.

Local Groundwater Management

On top of the "tragedy of the commons" dilemma, there are other significant barriers to effective groundwater management. It requires extensive knowledge of the geology of the basin, monitoring to determine inflow and outflow, and the interaction of groundwater with surface water.

Still, there has been significant success at the local level in managing groundwater. In a few cases, users have gone to court to settle questions over who gets how much. There are 22 "adjudicated" groundwater basins statewide, 21 of which are in Southern California. Users in these basins get an allocation of groundwater overseen by a watermaster, often DWR. There are also over 200 local groundwater management plans in existence, most of them in the Sacramento and San Joaquin Valleys.

The Legislature encouraged these local plans through the adoption of two measures in the early 1990s. AB 255 in 1991 authorized agencies in basins with "critical" overdraft issues to establish groundwater management programs in their service areas. That measure was expanded by AB 3030 the following year. However, as noted recently by the Legislative Analyst, the quality and thoroughness of these "AB 3030 plans" varies widely.

To that end, the Legislature enacted SB 1938 in 2002 to require, as a condition for receiving state groundwater grants, a jurisdiction to adopt a groundwater management plan that meets a number of criteria, including:

  • The adoption of basinwide management objectives related to groundwater levels, quality, land subsidence, and related changes in surface water.
  • Adoption of monitoring protocols which promote efficient and effective groundwater management.
  • Involvement of other local agencies with jurisdictions that overlie the groundwater basin.
  • Regulations further require periodic reporting of results and historical trends, and whether the management actions are achieving their objectives.

While an SB 1938 plan is required for groundwater-specific state grants, it is not known how many groundwater management plans comply with these requirements. DWR has not undertaken to review each local groundwater plan for these purposes, nor has the Legislature ordered or provided funding to do so.

The extensive funding provided for integrated regional water management (IRWM) plans have created an additional incentive for improving local groundwater management, as many localities are exploring conjunctive use and groundwater management as part of their IRWM plans. Eligibility for state groundwater remediation funds under the SBX7 2 (Cogdill) water bond is contingent on consistency with an IRWM plan, with preference given to projects that are part of a basin-wide management plan.

Emerging Issues

A movement is afoot to establish state-level management of groundwater resources. One of the stated purposes is to enhance storage and water supply reliability. In fact many local agencies, driven by market forces, are already employing their available groundwater storage for statewide benefit. Many agencies are ramping-up "conjunctive use" and "water banking" programs where managing entities contract with users to store surface water supplies underground in wet years and make them available in dry years. The Semitropic water bank, for instance, has approximately 450,000 acre-feet of storage currently open for contract and another 500,000 acre-feet under development. The Los Angeles Basin has reached a legal agreement that will pave the way for another 450,000 acre-feet in conjunctive use. DWR is undertaking a survey to find the extent of conjunctive use management across the state. These programs have the added benefit of restoring the local groundwater table over time.

As part of the 2009 water deal, the Legislature approved a new regime of monitoring and reporting of groundwater depths in all basins statewide. While SBX7 6 (Steinberg) avoided the imposition of a proposed tax or an outright mandate on groundwater users to pay for the program, there is already a proposal to re-evaluate program funding. The subject of a groundwater tax or charge is likely to be revisited in the near future.

SBX7 6 also requires DWR, for the first time since 1980, to do a thorough evaluation of all groundwater basins. The report is due in 2012 and, combined with the ongoing regulatory drought in regions overlying some of the most over-drafted basins, may induce another round of groundwater management legislation.

The importance of the regulatory drought to groundwater basins south of the Delta cannot be understated. Areas receiving only a fraction of their allotted surface water are forced to turn to heavier groundwater pumping for survival, as they have in past droughts. This situation is sure to exacerbate the findings of the SB 6 study. Actions to alleviate this issue will help stem the tide of groundwater depletion.

Should voters approve the SBX7 2 water bond this year, groundwater users will have access to $1 billion for remediation of contaminated basins, and part of the $2.25 billion for IRWM plans and $1 billion for water recycling where groundwater recharge is part of the recycling process.


Groundwater management poses a dilemma for users in a state where the right to groundwater is well-established. Improved monitoring and management is in their mutual best interest both for the sake of protecting the existing resource as well as future opportunities to use it for other purposes such as groundwater banking. With development pressures, it is also advantageous for local entities to explore their basins' potential in the near-term and possibly access vital recharge lands before they are lost. Furthermore, a well-managed basin protects both the rights of the groundwater users and holders of surface water rights. The state's role should be to continue to encourage such efforts, not to implement a costly, unnecessary and impractical system of statewide groundwater management that is inconsistent with the concept of groundwater as a property right.


For more information on this report or other Natural Resources & Water issues , contact Steve McCarthy, Senate Republican Office of Policy at 916/651-1501.