Alternative Water Supplies

Examples of alternative water resources. For ore information contact

From left, examples of alternative water sources.

Recycled Water, Desalinated Water, Stormwater, Graywater


Traditionally, California’s water supply comes from surface water (rivers and lakes) and from groundwater. But increasingly, we are looking to other sources for our water – referred to collectively as ‘alternative water sources’. 


These include:

  • Recycled Water: Water from a municipal wastewater plant that has been treated to the point that it can be safely used again.
  • Desalinated Water: Water from the ground or surface (e.g., brackish water or seawater) that has had the excess salts removed from it for use.
  • Stormwater: Water from runoff from precipitation events that is captured and sometimes treated for use.  The focus is not on reservoir releases for water supply or flood control.  Urban dry weather runoff is often discussed in this same context as stormwater.
  • Graywater: Wastewater from households or office buildings that does not contain human waste and that is diverted and sometimes treated for reuse for landscapes and for flushing toilets. 


Diversification of California’s water supply portfolio – using non-traditional water sources – improves our water supply reliability and our ability to withstand drought conditions.  Alternative water sources are crucial to that effort.

Also known as reclamation or reuse, water recycling is an umbrella term encompassing the process of treating wastewater and storing, distributing, and using recycled water. According to (Water Code § 13050) “’Recycled water’ means water which, as a result of treatment of waste, is suitable for a direct beneficial use or a controlled use that would not otherwise occur and is therefore considered a valuable resource.” Water can be recycled or reused on farms, within industrial complexes, and at home. However, municipal recycled water is what most people refer to as recycled water.

Municipal recycled water originates at a municipal wastewater treatment plant and is sewer water that has been collected, treated, and reused so that it can be beneficially reused again.

Municipal Water Recycling in California

Municipal recycled water has been safely and beneficially reused in California for more than 100 years. Since 1970, California has periodically quantified how much beneficial reuse is occurring in the state.

The most recent survey of municipal water recycling, conducted jointly DWR and the State Water Resources Control Board (SWRCB), found that California reused 714,000 acre-feet of municipal recycled water during 2015. This was an increase of 45,000 AF since the previous survey in 2009. This gain was achieved during the drought when mandatory water restrictions reduced flows to wastewater treatment plants. We expect to see significant increases in the next few years as projects that received Prop 1 or 2014 Drought Grant funding go online. A summary of the survey results presented at the recent IWA International Conference on Water Reclamation and Reuse held in Long Beach can be found in the Powerpoint presentations:

Dual Plumbing Code

The California Plumbing Code contains design standards to safely plumb buildings with both potable and recycled water systems. These statewide standards apply for installing both potable and recycled water plumbing systems in commercial, retail, and office buildings, theaters, auditoriums, condominiums, schools, hotels, apartments, barracks, dormitories, jails, prisons, and reformatories. These standards are found in Chapter 16A, Part II of the 2013 California Plumbing Code (California Code of Regulations, Title 24, Part 5). Chapter 16A is titled Non-Potable Water Reuse System, but informally this has been referred to as the Dual Plumbing Code. Due to copyright restrictions, printed copies of any portion of the California Plumbing Code must be obtained through the bookstore of the International Association of Plumbing and Mechanical Officials. 

Authorizing Legislation

California Recycled Water Task Force.  The initial basis for the dual plumbing code regulations was an analysis by the Recycled Water Task Force of the California Plumbing Code in effect in 2002, which incorporated dual plumbing code provisions from the Uniform Plumbing Code that were never officially adopted for California use and which were unsuitable for California conditions.

Over the course of nearly 14 months, the Recycled Water Task Force conducted a collaborative effort with many participants: recycled water experts, the public, and State staff. The Task Force adopted many recommendations to address obstacles, impediments, and opportunities for California to increase its recycled water usage. These recommendations target actions at various levels, and are not restricted to legislative actions or statutory changes. Many can be implemented by State or local agencies without further legislative authorization or mandate. The analysis and recommendations of the Recycled Water Task Force can be found in Water Recycling 2030: Recommendations of California’s Recycled Water Task Force, June 2003.

Water desalination is the removal of salts and dissolved solids from saline water (brackish or seawater), also known as desalting or desalinization. In addition to removing minerals, the process removes most biological or organic chemical compounds. Most desalination processes are based either on thermal distillation or membrane separation technologies. To learn more about water desalination, related issues, status in California and recommendations for a California strategy, see Chapter 10, Desalination (Brackish and Sea Water), in Volume 3 of the California Water Plan Update 2013.

California Desalination Planning Handbook 

DWR's California Desalination Planning Handbook is a guide for participants in water supply planning who are considering desalination options for water supply.  The question of whether to locally implement a desalination project can be complicated.  If a community determines desalination is appropriate for its needs, this Handbook is a guidance document for developing, where appropriate, economically and environmentally acceptable seawater and brackish groundwater desalination facilities in California. The planning process outlined in the Handbook is intended to identify and address the siting, regulatory, technical, environmental and other issues that should be considered in determining whether and how to proceed with a desalination project. 

California Water Desalination Task Force

In 2002, the California Legislature approved Assembly Bill 2717 (Hertzberg, Chapter 957), which asked DWR to convene the California Water Desalination Task Force to look into potential opportunities and impediments for using seawater and brackish water desalination, and to examine what role, if any, the State should play in furthering the use of desalination technology. A primary finding of the Task Force is that economically and environmentally acceptable desalination should be considered as part of a balanced water portfolio to help meet California's existing and future water supply and environmental needs. DWR prepared and submitted to the Legislature in 2003 the report, Water Desalination: Findings and Recommendations, to capture the valuable work of the Task Force

Mobile Water Desalination Units 

These units provide emergency water supply wherever and whenever needed. The units can be easily moved (via air, land or marine transport) and deployed to drought-stricken and water-stressed areas. Mobile desalination units provide flexibility in supplying potable water to communities by connecting to existing municipal water storage and delivery systems. They can also be quickly and easily decommissioned or moved to other locations should drought conditions ease. The report Logistics for Deploying Mobile Water Desalination Units was prepared in 2009 to address mobile desalination units.

Related Desalination Laws/Regulations

Cobey-Porter - 1965: Saline Water Conversion Law
Existing law California Water Code Sections 12946.-12949.6 declares that that the people of the state have a primary interest in the development of economical saline water conversion processes which could eliminate the necessity for additional facilities to transport water over long distances, or supplement the services to be provided by such facilities, and provide a direct and easily managed water supply to assist in meeting the future water requirements of the state.


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