No Longer Can We Think Of Groundwater As An Endless Resource

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Barcelona entered an emergency situation this week following 3 years of drought. Tight water restrictions will be implemented after water levels at reservoirs in the Mediterranean region fell below 16% of full capacity. The water use restrictions will affect nearly 6 million people.

Meanwhile, Spain’s outdoor cafes were brimming with patrons as unusually warm winter weather offered a break from indoor life. The pervasive fear in these outdoor spaces is that rising temperatures associated with the climate crisis bring threats of more heatwaves and ecosystem devastation.

“Catalonia is suffering the worst drought in the last century,” regional government chief Pere Aragones told journalists. “We have never faced such a long and intense drought since rainfall records began.”

What do these water restrictions look like?

• households and local councils are limited to 55 to 52 gallons per person;
• a ban on fresh water in swimming pools;
• cars must be washed with recycled water;
• showers in gyms are closed;
• watering in public parks is prohibited;
• the amount of water used to irrigate crops is cut by 80%;
• industries must cut water use by 25%.

Aragones insisted, “We will overcome the drought through cooperation, shared effort, planning, and well-directed investments.”

The region has built desalination plants and adopted other drought measures, but activists say it is crucial to improve the use of both wastewater and groundwater resources. “The drought is not just due to a lack of rain — it is the result of bad management,” Greenpeace argued in a statement.

It’s not just this region of Spain that is in trouble due to dwindling groundwater sources. An accelerated decline in water levels amid record droughts has been cited in South America, Iran, China, Australia, Colorado, California, Panama, and elsewhere.

Aquifers have fallen drastically almost everywhere in the world since 1980, but the decline has been most profound since 2000. How do we know? Over 170,000 groundwater monitoring wells and 1,700 groundwater systems over the past 40 years were analyzed by a group of researchers and published in the journal Nature. More than a third of the 1,693 aquifer systems — bodies of porous rock or sediment holding groundwater — monitored by the study fell by at least 0.1 m (3.94 inches) per year from 2000 to 2022, with 12% seeing annual declines of more than 0.5 m.

Groundwater-​bearing rock layers are known as aquifers — porous rock or sediment, sand, and gravel that is saturated with groundwater. Water enters an aquifer when precipitation or river water seeps into the soil or gravel bed; the water moves through the aquifer and emerges again through springs and wells. Groundwater is a major source of fresh water for farms, households, and industries, and depletion could pose severe economic and environmental threats, including falling crop yields and destructive land subsidence.

There is an additional danger on the coasts: if the groundwater level falls below a certain level, seawater can invade the aquifer. This salinizes the wells, leaving the water that is pumped up unusable for drinking water or for irrigating fields. Trees whose roots reach into the salinized flow of groundwater die.

“One of the most likely major driving forces behind rapid and accelerating groundwater decline is the excessive withdrawal of groundwater for irrigated agriculture in dry climates,” Scott Jasechko from the University of California, Santa Barbara, one of the paper’s co-authors, told Reuters.

Depletion has been particularly pronounced in arid climates with extensive croplands, as farmers are pumping out more groundwater to ensure their crops are irrigated, creating a devastating cycle. Agricultural water use in arid regions requires pumping huge amounts of  groundwater to the surface to irrigate crops. As the climate crisis creates drier and hotter conditions, agricultural crops need to be irrigated more heavily. Plus, as the world’s population continues to grow, more food needs to be produced.

Climate pollution made the drought 30 times more likely, drove extreme high temperatures, and contributed to lower rainfall, according to analysis by World Weather Attribution, an international group of scientists.

Experts say the climate crisis driven by human activity is boosting the intensity and frequency of extreme weather events, such as heat waves, droughts, and wildfires. “That’s why we can’t put the problem on the back burner,” says Hansjörg Seybold, Senior Scientist in the Department of Environmental Systems Science at ETH Zurich.  “The world must take urgent action.”

Climate pollution has caused record drought in the Amazon rainforest. Rivers are mud puddles, endangered dolphins are dying, and millions of people in the region struggle to sustain their traditional lifestyle. The drought that hit all 9 Amazon rainforest countries – including Brazil, Colombia, Venezuela, and Peru – is expected to worsen in 2024 after the rainy season begins to recede in May. The Amazon River, the world’s largest by volume, and several of its tributaries reached their lowest levels in 120 years of record-keeping last year, as the New York Times reports. One fifth of the world’s freshwater flows through the rainforest.

What can be Done to Save the World’s Groundwater?

What can be done to replenish and regenerate aquifers? Solutions start with suitable policy and other measures.

Where the climate crisis is driving a decline in precipitation, groundwater resources recover more slowly, if at all. In around 30% of the aquifers studied in the Nature article, some aquifers did improve over the period. That is partially because of local measures aimed at restricting how much water can be pumped out.

“The study also reveals good news,” says Nature co-​author Debra Perrone. “Aquifers in some areas have recovered in places where there have been policy changes or where alternative sources of water are available for direct use or for recharging the aquifer.”

The California Department of Agriculture outlines how groundwater recharge can occur in 2 ways – through natural percolation of water into the land surface, which is occurring during storms, or by diverting and conveying water to specific areas through managed recharge projects. Managed projects can capture water in rivers and streams at higher flows and move that water to various recharge facilities, such as open or agricultural lands to spread out and percolate into the ground, or specially designed percolation ponds.

A common solution is to reroute one water source to another to replenish depleted groundwater.

• The Genevese aquifer, which supplies drinking water to around 700,000 people in the canton of Geneva, replenished the aquifer artificially with water from the Arve River. The intervention stabilized the groundwater level initially and later raised it.
• In Spain, a large pipeline has been built to carry water from the Pyrenees to central Spain, where it feeds the Los Arenales aquifer.
• In Arizona, water is diverted from the Colorado River into other bodies of water to replenish the groundwater reservoirs – although this does cause the delta of the Colorado River to dry up at times.