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Groundwater Reliability Plus

What We Do

Groundwater Reliability Plus

Groundwater Reliability Plus 

About GWR Plus

EMWD’s Groundwater Reliability Plus (GWR Plus) initiative encompasses EMWD’s actions and investments to improve the quality and quantity of water in our local groundwater basins.

EMWD’s groundwater supply management has included enhancing water supplies through its recycled water program, desalination program, water use efficiency programs and, most recently, its healthy sewers program.

GWR Plus now includes a Water Banking project and a future proposed Purified Water Replenishment project that combines advanced water purification and natural filtration.

To learn more download our Groundwater Reliability Plus Brochure


Approximately 20 percent of EMWD’s potable (drinking) water demand is supplied by EMWD groundwater wells. The majority of the groundwater produced by EMWD comes from its wells in the Hemet and San Jacinto area. Some of these wells have limited production as a result of the Fruitvale Judgment and Decree. EMWD also has wells in the Moreno Valley, Perris Valley and the City of Menifee.

Contrary to the impression of groundwater being huge underground rivers and lakes, groundwater is the water that occupies the pores and cracks in soil and rock. The source of groundwater is either natural or artificial recharge.

Natural recharge begins as rain or snow that seeps directly into the soil and rocks, or from rivers, streams and lakes. Artificial recharge is the intentional recharge of water in ponds or spreading basins; or through the use of injection wells.

Groundwater basins may be defined by geologic structures, such as earthquake faults or fault zones; or, they may be defined by administrative boundaries based on water quality or some other factor. Groundwater flow follows a path of least resistance (i.e. groundwater level gradient) to a point of equilibrium.

WaterWise Plus

Learn more about ways to stay WaterWise Plus.

Recycled Water

EMWD’s recycled water program, which is among the most robust in the nation—meeting more than one-third of EMWD’s overall water supply needs. This program is continually expanded to help further reduce the demand on groundwater supplies.

Learn more about EMWD’s Recycled Water program.

Healthy Sewers

EMWD’s Healthy Sewers Program, a public education program that promotes the responsible disposal of prescription medication and fats, oils and grease. By reducing contaminants in the wastewater collection system, EMWD can reduce treatment costs, help sustain a high-quality recycled water supply and ultimately protect future groundwater quality.

Learn more about EMWD’s Healthy Sewers program.


In 2022, EMWD expanded its desalination program with the construction of its third groundwater desalination facility, the Perris II Desalter. This facility provides an additional 5.4 million gallons of capacity per day, enough to provide for approximately 15,000 households. This program will also further extract salt from some of EMWD’s local groundwater basins, helping to provide long-term water quality benefits.

Learn more about EMWD’s Desalination Program.

Water Banking

In 2021, EMWD completed its Mountain Avenue West Groundwater Replenishment Facility. Located in San Jacinto, it will allow for water imported from northern California during wet or normal years to percolate into local aquifers and be stored for use during normal or dry years. This project will also help improve water quality in the region and keep groundwater basins sustainable.

Learn more about Mountain Avenue West Groundwater Replenishment Facility.

Purified Water Replenishment (Future)

EMWD is planning an advanced water purification facility. Purified Water Replenishment starts with recycled water and purifies it using a multi-stage process of microfiltration and reverse osmosis. The purified water could then be blended with additional treated water before being pumped into replenishment basins, where it would go through a natural purification process which takes at least six months to filter through the ground. The water pumped from the ground would then go through one final cleaning step before it would be sent to homes and businesses.

Learn more about Purified Water Replenishment

Project Benefits

You never know when the next drought cycle will occur. To be better prepared for the future, we are investing in environmentally-sustainable projects that benefit our ratepayers and reduce our reliance on imported water.

  • Reduce water salinity to enhance groundwater quality
  • Higher regional groundwater levels and lower pumping costs
  • Increased groundwater availability
  • Drought-proof supply reliability and diversification

Frequently Asked Questions

Groundwater Reliability Plus

What is Groundwater Reliability Plus?

Groundwater Reliability Plus encompasses Eastern Municipal Water District’s (EMWD’s) actions and investments since its inception in 1950 to improve the quality and quantity of the water in local groundwater basins, also called aquifers. From its original water supply of local groundwater, EMWD added imported water when it became a member agency of The Metropolitan Water District of Southern California and has continued to add water sources through the years. The initiative now includes Water Banking, which provides long-term local water storage in the groundwater basins, and in the future will include Purified Water Replenishment, a combination of advanced water purification and natural filtration where the resulting water will also seep into the aquifer. Groundwater Reliability Plus also includes EMWD’s recycled water system, desalination program, water use efficiency and healthy sewers programs.

Groundwater Reliability Plus reduces water salinity and pumping costs, helps replenish groundwater aquifers, increases the amount of available local groundwater, and could ultimately provide a drought-proof local drinking water source.

Why are these new projects happening now? Can’t they wait until there is another drought?

EMWD has a responsibility to its ratepayers to proactively prepare to meet demands during normal, wet and dry water supply cycles. California has the most highly variable climate of any state in the U.S. and will face future droughts. Because these projects take years to design, permit, and construct – and we know that droughts are cyclical – EMWD is making the most of imported water whenever it is available to us so we can keep our groundwater basins full and improve the quality of water in them at the same time. With Water Banking beginning now and Purified Water Replenishment being planned for the future, these projects provide a local solution for the community’s long-term water needs.

Will Groundwater Reliability Plus help EMWD avoid cutbacks during future drought conditions?

Yes. By combining local resources with storing significant amounts of water within the service area, EMWD will be less vulnerable during dry periods. Much of the Water Banking project will be dedicated for dry year storage, meaning the water will not be used until an extended period of drought.

Does Groundwater Reliability Plus mean that EMWD will no longer rely on imported water?

EMWD is reducing its dependency on imported water by using it, when available, to improve the quality and quantity of local groundwater basins. As population increases, we will need to secure more supplies, both local and imported, so imported water will always make up part of the water supply. However, the goal is to develop more sustainable local water supplies and avoid increasing the amount of imported water that is used. We will keep our current water portfolio steady and balanced to the best of our ability so that almost half of our water supply will come from local sources.

This seems like a done deal – why wasn’t this reviewed more thoroughly with the public?

The most recent projects for the Groundwater Reliability Plus program are still in the early stages, and EMWD actively meets with community members and organizations to raise awareness about the benefits these projects could provide throughout EMWD’s service area. The environmental review process is also underway. As the projects advance to the design and construction phases, EMWD’s Board of Directors will vote in open session to approve the associated environmental reports as well as to approve necessary funding to complete final design and construction. The public will have the opportunity to address the Board of Directors during any Board meeting.

Who do we contact if we have further questions?

Please contact EMWD’s Public and Governmental Affairs department at 951-928-3777, extension 3430 or

Water Banking

What does the Water Banking project involve?

Water Banking puts water into local groundwater basins when water is plentiful, in the same way you might put money in the bank to save for times when you need it. The project includes construction of new facilities in the San Jacinto Basin, which will replenish the basin with water imported from the State Water Project during wet or average years for use during that same year or to store for the future.

How much more water can the groundwater basin hold?

It is estimated that the basin can hold an additional 200,000 to 400,000 acre feet of water on top of its current storage levels. The Water Banking project is estimated to add 20,000 to 30,000 acre feet of water to the basin during a wet year. In the future, the proposed Purified Water Replenishment project is estimated to add up to 4,000 acre feet per year during its initial phase. One acre foot of water is enough to serve 2 1/2 families for an entire year and is approximately 326,000 gallons.

Where exactly will the new Water Banking facilities be located and why were those sites chosen?

The replenishment ponds for Water Banking are located at Mountain Avenue and Esplanade Avenue in San Jacinto. That property is in the historic path of the San Jacinto River and has soil conditions that make it a prime location for replenishment operations.

When will the new facilities be online?

The Water Banking facilities were completed in Fall of 2021. Estimated dates for future projects such as the Purified Water Replenishment facilities will be dependent on additional studies.

Will there be a lot of construction in my neighborhood when you build these projects?

New pipelines will be needed for Water Banking, but they are not anticipated to go through residential neighborhoods. During Phase 2 of Water Banking, a new EMWD pipeline approximately six miles long will be constructed from Metropolitan Water District’s existing pipeline to the replenishment facilities.

Purified Water Replenishment

What is Purified Water Replenishment?

Purified Water Replenishment is a planned project that would blend advanced treated recycled water (purified water) with tertiary treated recycled water, which is currently used to irrigate food crops and landscaping throughout EMWD’s service area. This blended water would then be pumped to replenishment basins in San Jacinto where it will naturally seep into the ground and blend with existing groundwater.

While the State of California requires the water be underground for at least six months, groundwater modeling by EMWD shows the water will be traveling through the soil for approximately five years before it reaches EMWD’s groundwater wells. The water will then be pulled out through EMWD’s network of groundwater wells and be cleaned one final time at EMWD’s planned Hewitt and Evans Groundwater Treatment Facility. Continuous testing ensures the water meets all state and federal drinking water standards. It would then be sent into EMWD’s distribution system for drinking and other uses.

Is this Toilet to Tap?

No. There is no such thing as going directly from “toilet to tap.” There is no new water on earth; the same water is used and cleaned over and over again. Purified water is the product of a science-based process that uses advanced technologies, and this advanced treated water would then be blended with tertiary treated recycled water and pumped into groundwater replenishment ponds where it would go through an additional natural filtration process to provide a safe and sustainable local water supply.

What is the difference between purified water and tertiary treated recycled water?

Tertiary treated recycled water – sometimes referred to as “purple pipe” water – is wastewater that has been cleaned to make it suitable and safe for irrigation, industrial and other uses. Purified water is tertiary treated recycled water that has gone through a multi-stage process of microfiltration and reverse osmosis.

Are there other projects like Purified Water Replenishment?

In California, the most well-known similar project is the Orange County Water District’s Groundwater Replenishment System (GWRS), which has received significant media coverage since it began producing and placing 70 million gallons per day (mgd) of purified water into the groundwater basin there in 2008. This project has been highly successful in helping that region meet its water supply needs and was expanded to produce 100 mgd in mid-2015. It is now in its final expansion to be able to produce 130 mgd. The nearest similar project to EMWD is the Inland Empire Utilities Agency, which recharges its aquifer with 21,000 acre feet of tertiary treated recycled water each year.

Additionally, there are more than 30 planned or operating similar projects in California and many more nationally and worldwide. Most of these projects are similar in that they purify recycled water and put it into groundwater basins or surface water reservoirs.

Project Costs

How much will the new Groundwater Reliability Plus projects cost?

Cost estimates for the Purified Water Replenishment project will be available as it is planned and designed.

Will my water bill go up to pay for the new Groundwater Reliability Plus projects

Because water bills reflect the cost of purchasing and distributing water, as well as ensuring the water delivered complies with all drinking water standards—and the cost of cleaning up used water so it can be recycled throughout the service area—your bill will go up as these costs go up. However, EMWD works hard to secure outside funding to pay for new projects. To date, EMWD has secured tens of million of dollars in grants to support Groundwater Reliability Plus. Constructing projects that increase local water supply availability will help EMWD limit future rate increases associated with imported water supplies by maximizing the use of local water resources.

Most of the cost for the local water supply projects will be funded by the new connection fees paid by new development. Beyond that, EMWD customers already pay into a fund to help pay for projects that ensure long-term reliability and redundancy. In addition, EMWD is also actively seeking grant funding from the United States Bureau of Reclamation and through Metropolitan Water District’s Local Resources Program to offset the costs of the program.

Water Quality

Are there any published papers that show if there are any long-term health risks of projects like this?

There are no published papers that indicate that there are any long-term health risks associated with advanced water purification projects. Numerous water agencies have produced reports that detail testing and monitoring that show that purified recycled water is safe to drink and meets all drinking water standards. For example, Orange County Water District has voluntarily monitored for 400 compounds a day in the water for its GWRS project since that came online in 2008 and has not detected any problems. Testing and monitoring reports for the GWRS can be found here:

There’s frequently news about water quality reports showing trace quantities of disposed prescription drug compounds, hormones and personal care products in wastewater and surface water. How can you assure local residents the water will be safe?

EMWD conducts more than 40,000 water quality tests every year by highly-trained employees who carefully monitor and test the water at a state-certified laboratory before it is ever sent to drinking water taps. Purified Water Replenishment water will be no different, except that it uses technology that removes these substances of concern from the water before it is recharged into the ground. The replenishment process itself provides additional natural purification as the water seeps into the ground. EMWD always provides safe, high-quality water that meets or surpasses state and federal drinking water standards.

How can residents in EMWD’s service area help keep pharmaceuticals, pesticides and personal care products out of wastewater and groundwater?

Residents are encouraged to properly dispose of pharmaceuticals and other chemicals and not to flush those items down the toilet or pour them down the drain. EMWD’s Healthy Sewers campaign provides information to customers on how to protect the wastewater system by being Sewer Smart. For more information, please visit

Glossary of Terms

Learn more about Groundwater Reliability Frequently Used Terms


Mountain Avenue West Project Facility Renderings

Groundwater Aquifer

EMWD San Jacinto Valley Water Banking - Enhanced Recharge and Recovery Program EIR

In the News…

Where Water is Scarce, Communities Turn to Reusing Wastewater

EMWD Groundwater Replenishment Project Begins New Phase