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Flooding Fields for Aquifer Recharge

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During the recent drought, California farmers pumped so much groundwater that the water table dropped by 10 to 20 feet in some places, and up to 100 feet in others. Aquifers were depleted. Wells ran dry. And then, as if by some miracle, it rained.

This winter, storms have delivered rainfall from two to four times the average in California according to AccuWeather. More than 25 feet of snow has fallen over the high Sierra Nevada since mid-November, which translates to about 30 inches of water to be released into streams, reservoirs, and aqueducts. But storing this abundance of water for later use may prove challenging for the state.  

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Experts agree that groundwater storage represents a valuable solution to regional water storage needs. For one, it’s practical. California’s Department of Water Resources estimates the total groundwater storage capacity at somewhere between 850 million and 1.3 billion acre-feet. In comparison, surface storage from all the major reservoirs in California is less than 50 million acre-feet. Utilizing natural, subsurface storage is a logical solution.

It’s also cost effective. New research published by Stanford University’s Water in the West program shows that groundwater recharge is significantly less expensive—at a median cost of $390 per acre-foot—than surface storage options like reservoirs and tanks.

In order to replenish aquifers, surface water must find its way underground. Aquifers can be recharged naturally by way of rain, snow, and streamflow that soak into the earth, or artificially by channeling water into groundwater basins or by pumping water into aquifers.

Today, a group of farmers and researchers are attempting to help recharge the state’s aquifers by flooding fields. Flooded fields act like ponds that allow water to gradually permeate the ground and replace subsurface water.

“This is going to be the future for California,” Don Cameron, the general manager of Terranova Ranch, southwest of Fresno, California told NPRs Dan Charles. “If we don’t store the water during flood periods, we’re not going to make it through the droughts.” Over four months, Cameron flooded his fields with water—equivalent to three feet deep across 1,000 acres. “We started in February, and we flooded grapes continuously, for the most part, until May,” Cameron said. It all went into the ground, and didn’t seem to adversely affect his vines.

Helen Dahlke, a groundwater hydrologist at the University of California, Davis, and her team has set up test sites on almonds, pistachios, and alfalfa to test the effect of flooding on crops. “We really have to find new ways of storing and capturing rainfall in the winter, when it’s available,” says Dahlke. And there’s no better place, it seems, to safely and cost-effectively store water than underground.

What are your impressions of this diluvial method of aquifer recharge?

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  1. Laura———-what sits on top of the recharge areas to these aquifers will need consideration as this impacts the basin water quality. We here in California have not been all that careful in our husbanding of this resource. Take the Kern Water Bank as a tutorial in this. This basin was to be reserved as a major drought buffer for the south part of the state. Politics got involved and with some clever folk and that buffer was somehow transformed—it was a morphing of the original intent. Rather than a public trust, did it became a private entity? Then, additionally, sewage sludge from the Greater Los Angeles area and surrounding municipalities was imported and dumped on Kern County Pharms. Were these Pharms designed as waste disposal systems, masquerading as legitimate agriculture? For example, a Canadian colleague doing research on the practice of land application of sewage sludge audited some of these Pharms. It was found that while the US-EPA recommended loading limit for the land application of sewage sludge was 10 tons per year per acre, the audit saw 17 tons per month. The industry-driven EPA had shifted the designation of sewage sludge from a its original class as hazardous waste to its current class as a beneficial land amendment now called biosolids. Yet, if one gets into the public health and toxicology literature, a disturbing picture emerges. The interested reader may wish to read the following, which is the tip of the iceberg: I looked at Sugar Creek where this study was conducted, it is tributary to a much larger basis of water supply. Is runoff from agriculture still exempt from the provisions of the Clean Water Act? Do the provisions of the Safe Drinking Water Act really consider what is getting into our water resources—I fear not.

    Dr Edo McGowan

  2. Dr. McGowan is correct on several points. Recharging an aquifer can be tricky business. If done rapidly, you mix relatively pure water with water containing a large nutrient load and a host of other contaminents that are yet unknown. However, the approach of the California farmers is something to be considered. They are flooding their fields creating a wet land allowing the earth below to filter out the unwanted contaminents before reaching the aquifer. One area of concern is that the fields probably have a good bit of fertilizer and herbicide that can make its way down to the aquifer as well. It’s a better solution than surface storage where a great bulk of the water will evaporate and be of no use to the farmers until it rains again. Another thing to consider is the type of fertilizer that is applied. They may already do this, but a slow, time-released fertilizer cuts way down on the nutrient loading in the aquifer and surrounding bodies of water.

    1. Maybe wood chip mulch is the answer. This will absorb plenty of water and will fertilise the ground slowly as it breaks down over several years….

  3. I’m not a hydrogeologist, but I believe that it’s quite possible to create a surface wetland that produces vegetation with the nutrient loads associated with agricultural and natural runoff before direct injection into impaired aquifers, and harvest the resultant vegetation for use as compost and mulch which reduce the need for irrigation and fertilizer when applied to crops or ornamental landscapes. There are specific plants that can be included in the wetland that also absorb unwanted chemicals and metabolize them into non-toxic compounds.
    An example is the silage crop grown by Red Rock Ranch in the Westlands Water District that removes selenium from the soil/water and is a value added product for dairy feed in selenium deficient areas.
    There is even a mycelium that breaks down petroleum, and has been used to remediate oil spills.
    So all of this is possible, and practical. It’s also imperative that it move forward with a sense of urgency, because continued recharge deficits in our major aquifers reduce their capacity. The resultant subsidence of land is settling into the pores in the aquifers where water can be stored, due to the decrease in static pressure that results when the water level drops.
    It is also important to remember that runoff is important to the many species that are dependent on healthy streams and rivers, so we can’t covet or capture all of it in even the more efficient storage reservoirs that we call aquifers, unless we plan on eventually becoming the planet’s last species of fauna.
    It’s downright reckless, and probably even criminally negligent for someone who has been made aware of sound empirical data to wield their political power and spend Prop 1 $$$ to propose that we continue to develop highly inefficient and costly surface storage such as Sites Offstream Reservoir, or construction of Temperance Flat Dam on the San Joaquin River which is already so tapped that it has large stretches that run dry in all but the wettest years.

  4. Did, under political pressures, the US-EPA and Governor of California ignore the provisions of the Clean Water Act by allowing sewage sludge to be dumped on the surface overlying the Kern Water Bank?

    The 1972 amendments to the federal water pollution law that created what we call the CWA, provided mechanisms for grant moneys for the development of water quality management plans (Section 102 (c) (2), et seq). Title II grants were allocated for the construction of treatment works were administered through EPA. EPA was precluded from making grants to local governments that had not adequately studied various alternatives for management programs. Based upon guidelines prepared by EPA, each governor was to identify areas having substantial water quality problems. In addition plans were to contain alternatives for generated waste applicable to all wastes generated. This appeared to mandate continuing and vigilant efforts by the designee to ascertain where and what waste was generated or disposed within a plan area. There were further specific requirements to include a process to control disposition of all residual waste and a process to control disposal of pollutants to protect ground and surface water quality. Here Congress utilizes a term more inclusive than waste, i.e., pollutants.

    In 1977, the law was again amended (PL 95-217) and more money for grants made by EPA was made available, about $75 B in today’s dollars. These were termed mid-course corrections because Congress felt that a necessary restatement of the purpose of the Act was warranted. The Legislative History and Congressional Records indicated that implementation by EPA had been uneven and often contrary to intent and frequently more the result of judicial order than administrative initiative (clientele capture?). In their report to the Senate, the Conferees reiterated this theme several times. The members felt that the primary directions had been “inadequately addressed and often ignored”. There was to be no defense for the practice of allowing the dumping of waste into the nation’s water supplies.

    The Act was amended again in 1979 and again in 1981. By this time (late 1970s), the US-EPA had, through its main lab in Cincinnati, determined that sewer plants were actively generating multi-drug resistant bacteria in industrial volumes and then releasing those microbes to the environment and aquatic resources of the nation. The sewage sludge would be shown to carry high loads of these drug resistant microbes. Thus, it is a logical jump to worry about the land application of sewage sludge (biosolids). That report, all field and lab notes and the whole of the program history was subsequently expunged from the agency’s data base————why? In 2002, the NRC/NAS was asked to look at this issue and that scientific panel admonished the EPA to do more work on the topic of antibiotic resistance, stating the science being used was inadequate. To my knowledge, the agency never showed the NRC panel its previous work on sewer plant generated antibiotic resistance. Nonetheless, the dumping of biosolids continues. At what cost to water quality, hence public health?

    Dr Edo McGowan

  5. Do not bad mouth a Farmer with your mouth full. California has plenty of non ag land that can be flooded for percolation fields. Farmers need to spray and treat the crops more each year as the soil becomes more depleted of natural nutrients. Flooding farm fields is not the best idea for many reasons, let the farmers make the call for what is best for them. More wet lands are needed to offset urban development, Wetland plants have been shown to filter the water and remove harmful contaminants, support birds, bees and other wild life. California sends a lot of fresh water into the ocean all year long for many reasons however some that water should be overflow from wetlands and settling ponds. Sacramento at the river is only 13 feet above Sea level, that gives you a idea how flat and easy it would be to divert water into the central valley area for percolation ponds. Good common sense solutions and actions are met with opposition from state funded agencies and other so called tree hugger groups with grant money to spend on law suits and protesters. Did you know we have Animal rights protesters in California that want the slaughter of beef cattle to stop, they say , just buy your meat at the market. God help us.

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