Indecision, mismanagement, or misplaced priorities when dealing with water aquifers and distribution can have devastating effects on the environment and inhabitants. However, managed aquifer recharge (MAR) systems do wonders for an area’s water supply.
Aquifers are underground rock formations or sedimentary deposits porous enough to hold water. The U.S. Geological Survey describes them as “a geologic formation, group of formations, or part of a formation that contains sufficient saturated permeable material to yield significant quantities of water to groundwater wells and springs.”
According to the National Ground Water Association (NGWA), “MAR is the purposeful recharge of water to aquifers for subsequent recovery or environmental benefit.” MAR offers the opportunity to store surplus water during the wet season and in wet years for use during dry years and droughts.
The Interstate Technology and Regulatory Council, a program of the Environmental Research Institute of the States, stated on its managed aquifer recharge webpage, “Augmenting groundwater storage through managed recharge into aquifers represents a cost-effective way to increase the availability of source water, act as a barrier to saltwater intrusion, or serve as a method to stabilize the water table in stressed systems.”
Tim Parker, PG, CED, GHG, principal with Parker Groundwater in Sacramento, California, co-wrote the following in a 2022 Groundwater editorial:
MAR is not new by any means, having been practiced for decades and even centuries in some locales. Recharge water may be stored in a wide spectrum of confined and unconfined aquifer types, from unconsolidated alluvial deposits to karstic and fractured rocks. The current focus in many areas is on increasing and enhancing MAR to manage water supply through droughts and provide increased water supply reliability as demands grow and hydrology changes due to climate and human modifications of the land surface.
Getting Water Out
Parker said the U.S. has become adept at extracting water from aquifers. “We now realize that our focus needs to be on resources and energies to greatly increase our capabilities to capture and consistently recharge aquifers to have a long-term sustainable supply of water,” he said.
In California, aquifers offer five to 10 times the storage volume of surface water reservoirs, Parker said.
People vs. the Environment
Water availability has been a people-versus-environment issue, especially in terms of moving water from water-rich Northern California to water-poor Southern California, Parker said. “California had tremendous rainfall and flooding in the past year, very big gulps in the form of atmospheric rivers, and we lost a great amount of that water to the Pacific Ocean, although a fair amount of water remains in the renewed Lake Tulare,” he said.
“These big gulps came after the ‘five-year historic drought’ followed by a wet and normal year, and then the ‘three-year historic drought,’ and this sequence of events brought the issue of water availability to life for many people here, with many, many wells going dry during these droughts,” he noted.
“It also showed why it’s so important for the state and local water agencies to work together to take steps to put the infrastructure in place to enable greatly increasing capacity to capture and store water underground in aquifers,” said Parker.
In Southern California, a rare tropical storm hit in August this year, dropping between one inch and five inches of rain in a short period of time, flooding many areas, including the desert.
“Opportunities come and go,” Parker said. “You have dry years, and you have wet years. You have to take advantage of the wet years to prepare for the dry years and droughts, which we know will come. Our current infrastructure in California is not designed for the big swings in weather that we’re having. We need additional infrastructure to be able to capture the water and then store it underground in aquifers.”
Surface water systems are seasonal tools, not long-term solutions, Parker said. “We need to use the natural subsurface systems of aquifers that can store the water,” he said. “Yet, we also have so much seasonally available water during the really wet years because we’re in the part of the country where there are the most atmospheric rivers.”
Prioritizing Groundwater in California
California has been ground zero for many MAR discussions because it has significant groundwater declines that are even causing the land surface to sink, and the sinking is damaging infrastructure.
The Sustainable Groundwater Management Act (SGMA), passed in 2014 and enacted in 2015, prioritizes groundwater basins in California to help address the widespread groundwater depletion, and it requires that groundwater sustainability agencies be formed, these agencies develop groundwater sustainability plans, and groundwater sustainability is achieved within 20 years of plan adoption.
“We expect that good progress toward sustainability will be made under SGMA, but there are challenges as well, including funding to fill data gaps and build projects to become sustainable, and building consensus on the solutions for sustainability. Everybody does not always agree on the best solutions, who should pay and how much,” Parker said.
MAR’s Positive and Negative Effects
In the U.S., groundwater is a major resource, with 41 percent of the population relying on it for drinking water. It supplies fresh water for irrigation, domestic use, public use, industry, and mining, according to a 2020 report by the NGWA.
Groundwater accumulates over time after rain or other precipitation. Its availability depends on the amount of precipitation an area receives, which can fluctuate depending on the time of year. Groundwater depletion occurs when the natural replenishment process is too slow for the demands of a groundwater aquifer.
MAR can have both positive and negative effects on groundwater quality, according to the American Geosciences Institute (AGI). These effects depend on the water itself, the MAR technique being used, and the interactions between the recharged water and the aquifer materials, according to the AGI.
“Deep injection methods typically require more careful attention to water quality than surface recharge methods because the water is not naturally filtered by soil and rock above the aquifer,” the AGI shared on its MAR fact sheet. “Many projects therefore use stormwater for surface recharge only, or they treat the water before injecting it underground.”
According to the AGI:
- Surface recharge methods can use lower-quality water because the natural filter of soil and rock removes pollutants from the water before it reaches the aquifer, although not all types of pollutants can be removed in this way. Water quality risks are assessed and reduced using groundwater modeling and monitoring.
- Water storage is only possible in “closed” or “semi-closed” aquifers, in which the water does not flow from the injection site into deeper, inaccessible aquifers. Aquifers can also be “confined” (underneath an impervious layer that does not allow water to seep in from the surface) or “unconfined.” Deep injection methods are necessary for confined aquifers and in locations where there is little suitable land available for surface recharge, whereas surface recharge methods are especially suitable for “water table” aquifers just below Earth’s surface.
Water Rights, Permits Can
Get in the Way
Efforts to recharge aquifers are affected by who has water rights.
“If there’s excess water located, it should be available to us, but you need to establish that you have a right to that water to capture and store it underground,” Parker said. He added that state public agencies responsible for water supply need to know water will be available for recharge before they invest the money in the expensive infrastructure.
“You have to go through a state application process for obtaining water rights,” he said. “It’s not easy and takes time, although California is trying to make this work faster.”
In California, MAR was localized with the California Environmental Quality Act (CEQA) until 2014, said Mike Milczarek, president of GeoSystems Analysis, Inc., based in Tucson, Arizona.
CEQA was enacted in 1970 to ensure local and state agencies consider the environmental impacts of their actions and disclose to decision makers and the public significant environmental effects of their decisions when approving or rejecting a project.
State voters in California have approved eight water bonds since 2000 that authorize some $27 billion in funding for various water projects, but little of the money has gone to storage or flood control, according to the Wall Street Journal (WSJ). Just $2.7 billion of a $7.5 billion water bond that voters approved in 2014 was allocated for storage. None of the seven storage projects selected by the state for funding has begun construction, the WSJ reported.
“Blame in part a government permitting morass,” the WSJ said. “Most aren’t expected to be completed until the end of this decade, assuming they aren’t marooned by lawsuits.”
“There was a flurry of projects, but with so many regulations and players involved, it became difficult to accomplish much,” Milczarek said. “California is set up with its own standards mimicking much of the federal government, such as its own Environmental Protection Agency and Endangered Species Act. This creates opportunities for anyone opposed to the project to come in and slow it down.”
Andrew Ross wrote in an article published in Water in 2022, “MAR schemes have non-extractive environmental and social benefits and costs that cannot be easily measured or quantified.” Furthermore, “aquifer storage and recovery can improve water quality by diluting and treating pollutants.
“In connected groundwater and surface water systems,” Ross explained, “MAR can enable base flow and environmental flows to be maintained in dry times. While MAR schemes have significant energy requirements for groundwater pumping and treatment, these can be less than alternative sources of water supply.”
Situation ‘Opening a Lot of Eyes’
Oklahoma, Nebraska, Florida, New York, New Jersey, New Mexico, Colorado, and Arizona, among other states, also have MAR programs.
“What’s been happening lately in many parts of the country when it comes to water supply has been opening a lot of eyes,” Parker said.
Arizona’s 1980 Groundwater Management Act enabled the state to manage and protect groundwater for the benefit of residents across Arizona. Arizona did a lot of its major MAR projects in the 1990s and early 2000s. Today, most of the projects involve the expansion of existing systems.
Dry wells are used in Phoenix to capture storm water. The wells are three feet to four feet in diameter and drop 50 feet to 120 feet with gravel backfill. There are roughly 50,000 dry wells in Arizona. Southern Nevada and California also rely on them.
Lately, more attention has been paid to regulations involving dry wells and water quality, Milczarek said. “Given PFAs and PFOs and the potential for pathogens and other sediments, locals are looking more closely at them,” said Milczarek.
One way California is trying to address this is by working with farmers on flood-managed aquifer recharge (Flood-MAR). This strategy uses flood water to inundate fields of permanent crops when such waters are available, and it puts the water into aquifers from which the water was removed to grow crops.
“This can work,” Parker said. “But you need to know the composition of the soil and what crops the land is used for, how long ponds of water can sit on their land without damaging those crops, and what the potential water quality effects might be from legacy farming practices of using nitrogen and pesticide applications.”
Aquifer Storage Recovery an Option
R. David G. Pyne, PE, president of ASR Systems based in Gainesville, Florida, coined the term “aquifer storage recovery” (ASR) in 1982, pioneered the development of this technology, and has worked on ASR projects nationwide and overseas. His current ASR projects are in Florida, South Carolina, Texas, and California.
“When available, drinking water and water from other sources is stored deep underground through wells in fresh, brackish, and saline aquifers so that adequate water supplies will be available during droughts, peak demand periods, and emergencies, plus many other ASR applications,” Pyne said. “The stored water is then recovered from the same wells used for recharge.”
An ASR well is just like an aboveground storage tank, except it typically stores several hundred million gallons or more underground, not one million to five million gallons as in tanks aboveground.
ASR well depths are as shallow as 200 feet and as deep as 2,700 feet, and they are in consolidated and unconsolidated aquifers with a wide range of lithologies. Pyne estimates that there are now at least 700 ASR wells in at least 25 states and more than 140 well fields, plus many more in other countries.
Project funding has not been a major issue recently, he said. “When people start running out of water during a drought, they typically find a way to move ASR and other water supply projects forward rapidly. Of course, when it starts to rain, funding sometimes becomes more challenging,” Pyne said.
ASR Less Than Half the Cost
ASR is typically very cost-effective compared to other technologies providing similar water-storage benefits. Costs in most cases come in at less than half the cost of other water supply alternatives, Pyne said, and sometimes the cost savings have been closer to 90 percent.
ASR funding sources are plentiful, and Chuck Job at the NGWA recently produced a guide on funding sources for MAR, which covers both surface recharge and well recharge projects.
“If there is a problem with funding,” Pyne said, “it is more likely to be along the line of saving money by skipping steps typically recommended to ensure a successful outcome of an ASR or MAR project. There have been many ASR successes, hence the rapid and widespread implementation of ASR during the past 40 years.”
The biggest challenges have been opposition to ASR in a few states out of concern regarding recharge water quality and the potential for subsurface mechanisms that can potentially mobilize arsenic and other metals of concern.
“Almost all ASR wells are usually storing treated drinking water. However, several projects are underway or operational to store reclaimed water that is from advanced wastewater treatment plants, treating the water to meet drinking-water standards,” Pyne said. “Natural groundwater treatment processes occurring during ASR storage supplement water treatment aboveground, reducing or eliminating nitrogen, phosphorus, bacteria, viruses, protozoa, color, disinfection byproducts, and other constituents.”
About the author Paul Bergeron is a freelance writer based in Herndon, Va.