Tag Archives: groundwater

Iran’s groundwater resources are rapidly depleting, and everyone should pay attention

People have been relying on groundwater resources for all their drinking and washing needs since time immemorial. But some seem to be depleting fast when faced with today’s levels of demand, a new paper reports, explaining more than three-quarters of Iran’s groundwater resources are being overexploited.

Image credits Igor Schubin.

Over 75% of Iran’s land is faced with “extreme groundwater overdraft”, the paper reports. This describes the state where the natural refill rate of an area’s groundwater deposits is lower than the rate people are emptying them at. The paper was published by an international team of researchers led by members from the Concordia University, Canada.

Drying out

“The continuation of unsustainable groundwater management in Iran can lead to potentially irreversible impacts on land and the environment, threatening the country’s water, food, and socioeconomic security,” says Samaneh Ashraf, a former Horizon postdoctoral researcher now at the Université de Montréal, and co-author of the paper.

Mismanagement of these resources seems to be the biggest issue at play, the team explains. This exacerbates the obvious difficulties that a semi-arid country would have in securing water resources. Aquifers are further hampered by inefficient agricultural practices, which further drain them needlessly.

Without urgent action, the team notes, multiple, nationwide crises can arise when groundwater levels drop too low.

Iran has around 500 groundwater basins and sub-basins, and between 2002 and 2015, an estimated total of 74 km3 of water (73 billion liters) has been drained from them. This helped increase overall soil salinity across Iran and promotes land sinking (land subsidence). The Salt Lake Basin, where the country’s capital of Tehran is located is one of the most at-risk regions for land sinking.

This is quite worrying as the region, home to 15 million people, is already quite seismically active, and at risk of being hit by earthquakes.

Public data from the Iranian Ministry of Energy was used for the study.

“We wanted to quantify how much of Iran’s groundwater was depleted,” explains co-author Ali Nazemi, an assistant professor in the Department of Building, Civil, and Environmental Engineering at Concordia University. “Then we diagnosed why it was depleted. Was it driven by climate forces, by a lack of natural recharge, or because of unsustainable withdrawal?”

Agricultural use of water was the leading cause of aquifer depletion, they explain, with Iran’s west, southwest, and northeast regions being the most affected. These are agricultural areas where strategic crops like wheat and barley are grown. Consequentially, groundwater resources are most heavily depleted in these areas.

The number of registered wells for agricultural use has doubled in the last 15 years, they explain — from roughly 460,000 in 2002 to roughly 794,000 in 2015. Overall anthropogenic withdrawals of groundwater decreased in 25 of the country’s 30 basins over the same period, which suggests consumption is being concentrated in a few, overexploited aquifers.

Ground salinity levels are also rising across the country, too, as evidenced by soil electrical conductivity readings.

The national and local governments are not able to deal with this growing issue for a variety of reasons — including international sanctions, local corruption, and low trust among the population. However, the authors explain that both short- and long-term solutions are dearly needed in order to avoid these issues ballooning into huge crises.

“In the short term, the unregistered wells need to be shut down,” Nazemi says. “But longer term, Iran clearly needs an agricultural revolution. This requires a number of elements, including improving irrigation practices and adopting crop patterns that fit the country’s environment.”

Other countries would be wise to pay attention to what’s currently happening in Iran, Nazemi adds, and learn from their mistakes.

“Iran’s example clearly shows that we need to be careful how we manage our water because one bad decision can have a huge domino effect. And if the problem is ignored, it will easily get out of control,” he says. “It also illustrates the importance of environmental justice and stewardship. These are even more important when addressing the problem of climate change.”

The paper “Samaneh Ashraf et al, Anthropogenic drought dominates groundwater depletion in Iran” has been published in the journal Scientific Reports.

Our groundwater may be under more stress than we thought

Bad wells tend to be excluded from studies on groundwater quality which leads to biased assessments, a new study concludes. If this is the case, the state of the groundwater may worse than we thought in many parts of the world.

A fluid debate

Researchers from the University of Waterloo realized something was wrong with groundwater study when they noticed a major discrepancy between official data and anecdotal stories from southern India. According to data based on thousands of wells and satellite imagery, groundwater levels were rising steadily — which, in an area greatly relying on agriculture, is excellent. However, stories from farmers in the field told a different story.

Fieldworkers were hearing more and more stories from farmers about wells running dry — which suggests that levels were actually declining. It wasn’t just farmers complaining, there were also numerous reports of farmers digging deeper, more expensive wells because they couldn’t find water otherwise. The discrepancy was downright weird.

“If indeed groundwater levels are going up, why would farmers choose to pay more and dig deeper wells?” asked Nandita Basu, a civil and environmental engineering professor. “It didn’t make sense.”

In order to solve this issue, they combed through previous studies on groundwater, finding that wells with missing water levels were often excluded from the analysis because they were considered unreliable as data points. When these wells were added back to the data, the resulting picture fit much better with the stories from local farmers.

“They were systematically picking the wells with a lot of data and potentially ignoring the wells that were going dry because they had incomplete data,” said Tejasvi Hora, an engineering Ph.D. student who led the research.

A global issue

While the study was carried out on data from India, similar things are probably happening in many parts of the world.

It’s not just groundwater studies, either. Survivor bias artifacts can be easy to miss in science, producing numerous misleading results if not handled carefully. A quite literal example comes from a 1987 study on cats, which found that cats falling from more than six stories up are likely to have fewer injuries than cats falling from under six stories high — something which is probably caused by the fact that cats falling from more than six stories are often killed, and don’t end up in the vet for an injury report.

Similar examples of survivor bias in science appear in numerous fields of science, and researchers call more attention when it comes to data selection.

“Our main point is that bad data is good data,” she said. “When you have wells with a lot of missing data points, that is telling you something important. Take notice of it.”

“Whenever you’re focusing only on complete data, you should take a step back and ask if there is a reason for the incomplete data, a systematic bias in your data source,” Hora said.

The study was published in Geophysical Research Letters.

Water fountain.

Groundwater pumping is bleeding the US’s rivers dry

In certain cases, rivers have lost as much as 50% of their flow.

Water fountain.

Image via Pixabay.

New research led by a hydrologist at the University of Arizona warns that massive groundwater pumping since the 1950s is bleeding rivers dry. The findings can help shape policy for the proper management of U.S. water resources, the authors say, and should be of interest especially for states such as Arizona that manage groundwater and surface water separately.

Running low

“We’re trying to figure out how that groundwater depletion has actually reshaped our hydrologic landscape,” said first author Laura Condon, a University of Arizona assistant professor of hydrology and atmospheric sciences.

“What does that mean for us, and what are the lasting impacts?”

According to Condon, this is the first study to look at the impact of past groundwater pumping across the entire U.S. Other research has dealt with this issue, but only on smaller scales.

The team started by using computer models to see what the state of U.S. surface waters would have been today in the absence of human consumption. They then compared that with surface water changes recorded since large-scale groundwater pumping first began in the 1950s.

The model maps ground and surface waters onto a grid of squares (0.6 miles per side) that covers most of the U.S., excluding coastal regions. It included all the groundwater down to 328 feet (100 meters) below the land surface. The analysis focused primarily on the Colorado and Mississippi River basins and looked exclusively at the effects of past groundwater pumping because those losses have already occurred.

Estimates from the U.S. Geological Survey (USGS) place the loss of groundwater volume between 1900 and 2008 at 1,000 cubic kilometers. “The rate of groundwater depletion has increased markedly since about 1950,” it adds, peaking between 2000 and 2008 “when the depletion rate averaged almost 25 km3 per year (compared to 9.2 km3 per year averaged over the 1900–2008 timeframe).” One thousand cubic kilometers of water corresponds to one billion liters or 264.170.000 gallons.

“We showed that because we’ve taken all of this water out of the subsurface, that has had really big impacts on how our land surface hydrology behaves,” she said. “We can show in our simulation that by taking out this groundwater, we have dried up lots of small streams across the U.S. because those streams would have been fed by groundwater discharge.”

Too much of a good thing

Groundwater is a very valuable resource across the world. When surface water sources are scarce, absent, or overtaxed, groundwater is pumped to supply our domestic and economic needs. When misused, it can lead to enormous crises, like the one facing India today.

Among other things, it is also used for agriculture and provides hydration for wild vegetation. Some native vegetation like cottonwood trees will eventually die if the water table drops below their roots. In the United States, it is the source of drinking water for about half the total population and nearly all of the rural population, and it provides over 50 billion gallons per day for agricultural needs, according to the same article from USGS.

The team found that streams, lakes, and rivers in western Nebraska, western Kansas, eastern Colorado and other parts of the High Plains have been particularly hard hit by groundwater pumping. Those findings agree with other smaller-scale studies in the region.

“With this study, we not only have been able to reconstruct the impact of historical pumping on stream depletion, but we can also use it in a predictive sense, to help sustainably manage groundwater pumping moving forward,” says Reed Maxwell, the paper’s co-author.

“We can do things with these model simulations that we can’t do in real life. We can ask, ‘What if we never pumped at all? What’s the difference?'”

The regions that were most sensitive to a lowering water table are east of the Rocky Mountains, where the water table was initially shallow (at the depth of 6-33 feet or 2-10 meters). Ground and surface waters are more closely linked in these areas, so depleting the groundwater is more disruptive for streams, rivers, and by extension, vegetation. The western U.S. has deeper groundwater, so reducing their volume didn’t have as powerful an effect on surface waters.

Condon says that other research has shown that the areas of the Midwest where precipitation used to equal evaporative demand — i.e. where irrigation wasn’t required for crops — are becoming more arid. Those are some of the regions where groundwater pumping has reduced surface waters.

“In the West, we worry about water availability a lot and have many systems in place for handling and managing water shortage,” Condon said. “As you move to the East, where things are more humid, we don’t have as many systems in place.”

The paper “Simulating the sensitivity of evapotranspiration and streamflow to large-scale groundwater depletion” has been published in the journal Science Advances.

Boron found on Mars – a signature of long-term habitable groundwater

The Curiosity Rover has found boron on the surface of Mars – a strong indication that the Red Planet once hosted long-term habitable groundwater, making it even more likely that life once existed on Mars.

ChemCam target Catabola is a raised resistant calcium sulfate vein with the highest abundance of boron observed so far. The red outline shows the location of the ChemCam target remote micro images (inset). The remote micro images show the location of each individual ChemCam laser point (red crosshairs) and the B chemistry associated with each point (colored bars). The scale bar is 9.2 mm or about 0.36 inches.
Credit: JPL-Caltech/MSSS/LANL/CNES-IRAP/William Rapin

The exciting discovery was announced at the American Geophysical Union conference. Because boron is associated with arid sites where much water has evaporated away, the perspectives are obviously intriguing.

“No prior mission to Mars has found boron,” said Patrick Gasda, a postdoctoral researcher at Los Alamos National Laboratory.

Here on Earth, similar traces can be found in California or other arid areas which were once rich in water. If this is also the case on Mars, then everything would align to make Mars suitable for extraterrestrial life.

“If the boron that we found in calcium sulfate mineral veins on Mars is similar to what we see on Earth, it would indicate that the groundwater of ancient Mars that formed these veins would have been 0-60 degrees Celsius [32-140 degrees Fahrenheit] and neutral-to-alkaline pH.” The temperature, pH, and dissolved mineral content of the groundwater could make it habitable.

The environmental implications of the boron and how exactly it came to be is still a matter of debate. It could be that the drying out of a lake resulted in a boron-containing deposit in an overlying layer, not yet reached by Curiosity. Some of the material from this layer could have later been carried by groundwater down into fractures in the rocks. Yet it could also be that the chemistry of clay-bearing deposits and groundwater affected how boron was picked up and dropped off within the local sediments. Either way, while there is still some debate going on, the evidence seems to indicate to a water-rich past, and one that could support life.

This type of active groundwater acts like a chemical reactor in a way. It dissolves old minerals, creates new ones, and generates a redistribution of electrons – all reactions which support the emergence of life. These dynamic processes are visible in the mineral veins that filled cracks in older layered rock. But this also affected the composition of that rock matrix surrounding the veins, and the fluid was in turn affected by the rock.

“There is so much variability in the composition at different elevations, we’ve hit a jackpot,” said John Grotzinger, of Caltech, Pasadena, Calif. As the rover gets further uphill, researchers are impressed by the complexity of the lake environments when clay-bearing sediments were being deposited and also by the complexity of the groundwater interactions after the sediments were buried.

The discovery of boron is just one of several exciting findings on Mars, but at the moment, we still don’t know for sure whether life did exist on Mars. The circumstantial evidence is strong, but at the end of the day, it’s still circumstantial evidence. But the stars are starting to align, and the future might hold some interesting things.

The San Ardo Oil Field From the Coast Starlight. Credit: Wikimedia Commons

Scientists find three times more groundwater beneath California’s Central Valley — but a third may already be contaminated

The San Ardo Oil Field From the Coast Starlight. Credit: Wikimedia Commons

The San Ardo Oil Field From the Coast Starlight. Credit: Wikimedia Commons

Stanford researchers found California’s drought-struck Central Valley harbors three times more groundwater than previously thought. That’s bound to come as great news, especially for the farmers who have never seen a water shortage of this kind for 1,200 years.

The researchers, however, stress that the quality of the water is largely unknown. Thousands of oil well stretching from L.A. to Sacramento may have irreversibly contaminated an important fraction of the newly discovered aquifers.

Going deeper than ever before

“It’s not often that you find a ‘water windfall,’ but we just did,” said study co-author Robert Jackson, the Michelle and Kevin Douglas Provostial Professor at Stanford. “There’s far more fresh water and usable water than we expected.”

Previous estimates of California’s water were based on decades-old data and only extended to a maximum depth of about 1,000 feet. But nowadays technology enables us to tap into much deeper aquifers, something that farms and even some residents have been doing for years already. The most severe drought in California’s recorded history is also a strong motivator to invest in deep drilling for water despite only five years ago it wouldn’t have made economic sense.

Using data from 35,000 oil and gas wells, the Stanford researchers were able to characterize shallow and deep groundwater sources in eight California counties. They estimate usable groundwater in the Central Valley amounts to 2,700 cubic kilometers or triple the previous estimate of the state’s water supply.

The findings, though important, are far from being a solution to California’s growing water problem. All of this plentiful water is located between 1,000 and 3,000 feet underground, which makes extraction very expensive. Drilling this deep for water also increases the risk of ground subsidence or the gradual sinking of the land, something that is already happening more often in the Central Valley where some regions have dropped by tens of feet.

Then there’s the issue of quality, which seems to be a gray area at this point since we lack extensive on-site studies. Judging from what data they have at their disposal, the Stanford team says deep aquifer water has a high concentration of salt, so a desalinization process is required to make use of it — yet again, very expensive.

Some water might also be contaminated beyond repair by the numerous oil wells that litter the Central Valley. Right now, many oil and gas wells are drilling directly into usable freshwater or 30 percent of the newly found aquifers.

“We don’t know what effect oil and gas activity has had on groundwater resources, and one reason to highlight this intersection is to consider if we need additional safeguards on this water,” said Jackson, though he later stresses that water near a fracking site doesn’t necessarily mean it’s contaminated.

“What we are saying is that no one is monitoring deep aquifers. No one’s following them through time to see how and if the water quality is changing,” said study co-author Mary Kang, a postdoctoral associate at Stanford School of Earth, Energy & Environmental Sciences. “We might need to use this water in a decade, so it’s definitely worth protecting.”

Yes, we need to protect this water — now, more than ever. However, current EPA guidelines say drillers can operate wells under aquifers if these are not currently being used for drinking water and “cannot now or will not in the future serve as a source of drinking water.” An example of an aquifer that can’t be used as a source of drinking water is a contaminated one. Times have changed, though, and an aquifer 2,000 feet deep can now be called useful. Think Progress reports the Center for Biological Diversity wants to encourage the EPA to reject the applications for aquifer exemptions filled by oil & gas companies looking to drill in new wells.

“I hope that it becomes clear that we need to just not issue any more aquifer exemptions and we need to stop this process of sacrificing our groundwater and start the process of thinking about how we’re going to move beyond that,” Maya Golden Krasner, a staff attorney with the Center for Biological Diversity, told ThinkProgress.

Scientists reveal the first global groundwater map to date

A team of North American researchers has analyzed a swarm of data and created the first map that tries to estimate how much water is located beneath the Earth’s surface.

Image credits: Karyn Ho

Earth and Water

We tend to think of the water cycle as something that happens above ground, but there’s a lot of water beneath ground – an estimated 23 million cubic kilometers – that’s enough to cover the entire surface in a layer of water about 180 meters thick. In order to come up with this figure, researchers analyzed data from almost a million watersheds, as well as over 40,000 groundwater models; somehow, they managed to integrate all that together and the results can be seen in Nature. They included information on the permeability of rocks and soil, on their porosity, and all that is known about water table gradients. Another important piece of information was the collection of tritium measurements. Tritium is a radioactive isotope of hydrogen that spiked in the atmosphere 50 years ago as a result of thermonuclear bomb tests, and therefore can be used as a trace marker to figure out if the water has been recycled recently.

So how exactly is water stored underground? Well, in most places, the ground is not fully compact, and there are many pores and cracks through which water can slip. It may seem quite small, but you can reach some huge quantities of water through this. But while that may be a lot, only 5.6% of it is actually integrated in the global water cycle – the so-called modern water. This modern water is extractable and usable for human purposes, “It’s the groundwater that is the most quickly renewed – on the scale of human lifetimes,” explained study leader Tom Gleeson from the University of Victoria.

“It’s the groundwater that is the most quickly renewed – on the scale of human lifetimes,” explained study leader Tom Gleeson from the University of Victoria. And yet this modern groundwater is also the most sensitive to climate change and to human contamination. So, it’s a vital resource that we need to manage better.”

The tap might run out

This raises new concerns about global water reserves, which have been dipping worryingly in recent years; almost a third of the global population, over 2 billion people rely strictly on groundwater for drinking water and growing crops. These resources are also most vulnerable to over-usage. Water is most definitely not an infinite resource.

Writing Nature Geoscience, Ying Fan, from Rutgers University, US, commented that “this global view of groundwater will, hopefully, raise awareness that our youngest groundwater resources – those that are the most sensitive to anthropogenic and natural environmental changes – are finite”.

In terms of the map they created, it shows the distribution of this modern groundwater – dark blue shows where it’s quickly renewed, and light blue shows the areas which renew less often, or which are non-renewable at all. If you overlay it on a geographical map, you see that many of the deep blue areas coincide with mountainous areas. Knowing how much water is non renewable is important to estimate how much water we can still use.

“Since we now know how much groundwater is being depleted and how much there is, we will be able to estimate how long until we run out,” he said.

Demand for water bigger than supply

Groundwater use is unsustainable in many of the world’s major agricultural zones; as a matter of fact, about a quarter of the world’s population lives in regions where groundwater is being used up faster than it can be replenished, concluded researchers.

The planet thirsts

Picture from the study. Click it for full size.

Our entire civilization depends on our water supply, and aside from agriculture, pretty much all industrial processes require vast quantities of water – water that has been stored up to thousands of years in various aquifers. Aquifers are underground layer of water-bearing permeable rock or unconsolidated materials from which groundwater can be extracted with wells. Some aquifers are absolutely massive, stretching across several countries and providing agricultura, industrial and drinking water for millions and millions of people. However, in most of the world’s major agricultural areas, including the Central Valley in California, the Nile delta region of Egypt, and the Upper Ganges in India and Pakistan, the demand is larger than the supply.

“This overuse can lead to decreased groundwater availability for both drinking water and growing food,” says Tom Gleeson, a hydrogeologist at McGill University in Montreal, Quebec, and lead author of the study. Eventually, he adds, it “can lead to dried up streams and ecological impacts”.


It’s not that the planet doesn’t have enough water – the truth is that we’re using it recklessly. Gleeson and his colleagues combined a global hydrological model and a date set of groundwater use to estimate how much water is extracted by countries throughout the world. They also analyzed another important factor: the aquifers’ rate of recharge – the speed at which groundwater is replenished. Using this approach, they managed to calculate the groundwater ‘footprint’ for nearly 800 aquifers worldwide; and the importance of this study is huge.

“To my knowledge, this is the first water-stress index that actually accounts for preserving the health of the environment,” says Jay Famiglietti, a hydrologist at the University of California, Irvine, who was not involved in the study. “That’s a critical step.”

The authors found that some 20% of the world’s aquifers are being overexploited – some heavily so. For example, the the groundwater footprint for the Upper Ganges aquifer is more than 50 times the size of its aquifer, so the rate of extraction is highly unsustainable, Gleeson notes – a dramatic fact, considering how over 200 million rely on water from that aquifer.

The truth is dire, Gleeson estimates. He believes that a even more thorough study would find even more aquifers in dramatic, unsustainable situations. But, he also adds, there is still hope: as much as 99% of the fresh, unfrozen water on the planet is groundwater. “It’s this huge reservoir that we have the potential to manage sustainably,” he says. “If we choose to.”