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CIRS Blog about Rural California

Groundwater storage and delivery infrastructure in California

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By Annie Beaman and Poppy Davis                                                  


This is the second of four briefs on California’s water infrastructure by CIRS and partners. This brief focuses on ground water management. A third brief will address water quality and the fourth will summarize significant proposals to address California’s water needs. The goal of these short papers is to provide a road map to understanding the conversation around California water issues. All briefs will be featured on the Rural California Report and will be available as downloadable files. Here is a PDF version of this brief: CA-Groundwater-Storage-and-Delivery-Brief.pdf


Importance: Over 850 million acre feet of water is stored in the state’s 450+ groundwater reservoirs. Groundwater is a critical resource in California, supplying an average of 30-40% of total water statewide, and upwards of 60-70% in dry conditions. California consumes far more groundwater than any other state, pumping an average of 10-15 billion gallons per day.

Recharge: Groundwater recharge occurs naturally when surface water from precipitation, rivers and streams, and irrigation runoff percolates through the soil to aquifers. Aquifers are underground formations of permeable rock that can contain and transmit groundwater. Artificial recharge programs allow excess surface water to be stored and released slowly through canals, irrigation furrows or sprinkler systems, or spread on dedicated recharge fields for percolation into these same underground “reservoirs.” In some cases, water is injected directly into the subsurface via wells.


Overdraft: Groundwater overdraft occurs when water is withdrawn at a faster rate than it can be replenished. Aquifer levels change from year to year based on environmental and other factors, and regular monitoring combined with responsible management can prevent long-term groundwater depletion. Overdraft contributes significantly to water quality problems in aquifers[i] and salinization of coastal aquifers, because the effects of groundwater pollution and sea water intrusion are magnified when water levels are low. Overdraft can also cause subsidence, wherein the land above depleted aquifers sinks downward. Imported water from statewide water programs can supplement the total amount of water available for use in overdrafted areas, but can rarely restore underground water levels completely.[ii]

Management: Groundwater is managed locally in California; there is no statewide law that governs the use or management of this resource, nor any requirement that local authorities report their activities to the state.[iii]  Literally hundreds of local water agencies and authorities oversee groundwater delivery infrastructure including pumping wells and irrigation systems. Under common law, private landowners have “overlying” or “correlative” rights to use groundwater, meaning that each owner may operate wells and irrigation systems that use “reasonable” amounts of water for “beneficial” purposes—broad categories that generally lack statewide regulation or oversight.[iv] California is the only remaining western state without a statewide groundwater management system in place. Instead, disputes over groundwater are addressed at the local level and by courts.


There are three general categories of groundwater management entities:

Local agencies granted specific authority by the CA Water Code or by state statute

Local groundwater ordinances or Joint Powers Agreements (JPAs)

Court adjudications over water disputes that result in appointments of local “water masters” who are granted authority to control groundwater extraction and use

 Integrated Regional Water Management Plans (IRWMs) approved by the California Department of Water Resources (CA DWR) can qualify communities for state-funded grants to manage groundwater quality and quantity. The IRWM Program funds regional water projects that can cross jurisdictional, watershed, and political boundaries while involving multiple agencies and communities. IRWMs often integrate surface water infrastructure with groundwater management practices. The goal of the IRWM Program is to provide support for regional water solutions that are mutually beneficial to the stakeholders in a given area of the state.[v]

Conjunctive management projects integrate surface and groundwater infrastructure by storing water for later use, and/or releasing water gradually for managed groundwater recharge and stream flows. Many conjunctive management programs provide additional benefits including hydropower, flood control, water quality improvement, wildlife habitat, recreation, and decreased reliance on Delta water. Groundwater storage is especially essential for local districts because allocations from statewide water projects can be cut during dry years.

Examples of conjunctive management projects:

The Santa Clara Valley Water District (SCVWD) was formed in the early 20th Century, and formalized in 1968 by an act of the California Legislature. By 1935, the SCVWD operated extensive surface water infrastructure (i.e. dams and reservoirs) as well as percolation facilities for groundwater recharge. As local population and water use increased, SCVWD began importing water from statewide water projects to avoid prolonged overdraft. Groundwater levels recovered as recharge and storage infrastructure improved.  Currently, the SCVWD manages an extensive, interconnected system of surface and groundwater to ensure local demand is met regardless of conditions. Managed releases of surface water recharge aquifers throughout the year, and also provide critical services including stream habitat for threated fish. 

The Yolo County Flood Control and Water Conservation District (YCWD) was created as an independent “special district” by an act of the California Legislature in 1951. For over 50 years, the YCWD has monitored groundwater levels through an unusually extensive network of wells. The operational strategy of the YCWD maximizes water storage in the groundwater basin, and has maintained healthy levels throughout the years.

The Tulare County Irrigation District (TCID) was organized on September 21, 1889 for the purpose of managing, supplying, and delivering water to growers in the Tulare area. This area provides an example of the interaction of surface and groundwater. TCID manages one of the most overdrafted aquifers in the state, the Tulare Lake Basin. The region has had nitrates from agricultural fertilizers and animal wastes percolating into the soil for decades. Now nitrates are being detected in the aquifer causing public health concerns for regional residents who use well water for drinking. A majority of residents living in this sparsely populated rural region are not connected to municipal water and draw from small community water sources or private wells that are contaminated.[vi] 


[i] NOTE: California’s groundwater quality will be addressed in the next brief in this series.

[ii] San Luis Reservoir is an example of a major asset that supplements groundwater recharge and irrigation water in Fresno, Kings, and Merced Counties. This is a joint federal/state project, primarily storing surface water, and also providing multiple benefits including electricity generation, recreation, and flood control.  http://www.usbr.gov/projects/Project.jsp?proj_Name=San%20Luis%20Unit%20Project 

[iii]CA DWR Groundwater Management Districts or Agencies in California (1996). Accessed online at  http://www.water.ca.gov/pubs/conservation/waterfacts/ground_water_management_districts_or_agencies_in_california__water_facts_4_/water_facts_4.pdf NOTE: State and Federal laws apply to water quality, including groundwater and drinking water quality, which will be discussed in a subsequent brief

[v] CA DWR IRWM Grant Program Information http://www.water.ca.gov/irwm/grants/

[vi] Addressing Nitrate in California’s Drinking Water. Harter and Lund, 2012.  http://groundwaternitrate.ucdavis.edu/

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Annie Beaman is an independent consultant working on water issues and sustainable agriculture in California. In addition to researching, writing, strategizing, and campaigning about issues that impact vulnerable ecosystems and communities, she is an avid gardener and baker. Annie is a stewardship-obsessed member of a multi-generational farming family, and a longtime advocate for environmental protection and social justice. Follow her on Twitter @anniebeaman.


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