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Recharging aquifers with recycled water may be enough to prevent wells from going dry.

When an aquifer is tapped dry, often it’s lost forever as a source of water

The groundwater in underground aquifers is one of our most indispensable natural resources, but overuse and contamination from human activities are severely endangering aquifer viability, leading to economic troubles, public health ills, and even water conflict. Once an aquifer is depleted, the ground above it tends to subside into the empty space and closes off the aquifer forever. Right now, human activities are draining aquifers far faster than natural systems can replenish them. What will groundwater-reliant populations do when their aquifers can no longer be used?

Reliance on Groundwater

In 2015, approximately 29% of the fresh water used in the United States was sourced from aquifers. A third of the water rural and municipal water departments deliver to households and business is pumped from aquifers, and 90% of the rural population depends on groundwater for its drinking water. Even some major metro areas, like San Antonio, rely exclusively on groundwater. Nationally, agriculture gets 48% of its irrigation water from aquifers. Where surface water bodies are lacking, like in the American West, groundwater’s importance is magnified.

Groundwater makes up as much as 33% of global water withdrawals. More than 2 billion people count on groundwater as their main source of water, and 50% of agricultural irrigation water is pumped from aquifers. It’s a key reserve during prolonged droughts like those in the American West, Brazil, and Australia.

Without groundwater, global water security is far more fragile. But despite its vital importance to humanity, groundwater gets far less attention than rivers and reservoirs, perhaps because it is less visible. But whether we can see it or not, the areas of the world that are most reliant on groundwater are depleting it far faster than it can be replenished by natural processes.

Critical aquifers, most of which irrigate the most productive agricultural regions in the world, include those in:

  • The North China Plain
  • Australia’s Canning Basin
  • The Northwest Sahara Aquifer System
  • The Guarani Aquifer in South America
  • The High Plains and Central Valley aquifers of the United States
  • Northwestern India and Pakistan
  • The Middle East

Threats to Groundwater

Population growth is one of the major threats to aquifers. More humans mean more human activities, whether household, agricultural, or industrial. Industrialization and rising living standards are contributing to water demand.

The aquifer under Karachi, Pakistan, is enormous, but it is contaminated with industrial arsenic and, to make matter worse, it is being progressively depleted. In Pakistan, 40% of deaths are attributed to contaminated water. But contamination is not just a problem in the developing world. Much of rural America’s drinking water is suffering from nitrate contamination from agricultural fertilizer.

In Texas, where state officials recently proclaimed they were “about three Lake Meads” short of water, human activities and evaporation do not always explain the aquifer depletion, and the solution to the mystery remains elusive.

Large areas of the Jakarta, Indonesia, are quickly sinking into the Java Sea. One might expect to hear the problem is climate change-associated sea level rise, but aquifer depletion is the greater problem. When aquifers are emptied under the city, the land under the city begins to subside.

And that goes for rural agricultural land on the other side of the world in California. San Joaquin Valley growers have depleted their aquifer so severely that in some places, the ground has subsided more than 20 feet, and the loss of the aquifer’s water storage capacity is considered to be largely permanent.

Depletion in coastal areas worldwide also leads to saline intrusion into aquifers as seawater seeps in to fill the void, rendering aquifers brackish and unusable for most purposes without treatment. In central and Southern California, water management is injecting fresh water into aquifers to halt saline intrusion.

Finally, a new study has determined that there is far less fresh water than thought in U.S. aquifers, but the implications of the discovery are global.

Ways to Protect Groundwater

Natural systems cannot recharge heavily used aquifers faster than growing populations deplete them, but we can help replenish them. The use of pervious concrete pavement, for instance, allows water that might have been disposed of in gutters to percolate into aquifers. Managed aquifer recharge (MAR) identifies sites that are ideal for water to enter aquifers and diverts water to them.

California growers, in partnership with local authorities, are diverting excess river flows during wet years into “water parking lots,” which allow the water to percolate into the aquifer for use in dry years.

Wastewater Reuse

Where there is no water to divert, even raw sewage can be converted into high-quality effluent that can replenish groundwater.

In California, cutting-edge water reuse technology, such as Fluence’s membrane aerated biofilm reactor (MABR), has been certified at Stanford University to conform to strict California Title 22 standards. Due to its simultaneous nitrification-denitrification, MABR has very high nutrient removal and produces effluent suitable for managed aquifer recharge and agricultural reuse.

Fluence provides MABR in two lines of products, Smart Packaged Aspiral™, which is suitable for decentralized treatment, and SUBRE, which allows existing wastewater treatment plants to be retrofitted with MABR modules.

Brackish Water Aquifers

Where saltwater has already contaminated aquifers, brackish-water desalination is an option that is becoming ever more viable. In fact, brackish water is easier and less expensive to desalinate than seawater. With technological advances dropping the high price of desalination, the desalination of brackish groundwater is becoming more and more viable.

In the U.S., there are vast brackish aquifer water reserves in coastal areas suffering from saltwater intrusion. Notably, in Texas there are 880 trillion gallons lying unused in brackish aquifers.

Also, in a discovery with global implications, a brackish aquifer under 15,000 square miles of seabed was recently found in the Atlantic off the coast of the U.S. Northeast. Although the area has not yet suffered water shortages that justify tapping brackish aquifer, scientists say the discovery infers such undersea aquifers may be common worldwide, offering a virtually limitless supply of water that is much more readily desalinated than seawater.

A range of Fluence products can help communities safely convert their wastewater into a high-quality effluent to restore their aquifers or allow them to sustain themselves on brackish water reserves. On Cyprus, for instance, a Fluence desalination plant uses brackish water reverse osmosis and has a capacity 10 million L/d of top-quality drinking water. In China, Fluence is commissioning 80 Aspiral MABR wastewater treatment plants that will allow Hubei Province highway service areas to safely replenish the local environment with high-quality effluent.

Contact Fluence for the technology and expertise to turn brackish water into high-quality drinking water and safely replenish aquifers.

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