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Written by: Scott Jasechko, University of California, Santa Barbara; Debra Perrone, University of California, Santa Barbara, and Richard Taylor, UCL

Published: 27 January 2024

 

If you stand at practically any point on Earth, there is water moving through the ground beneath your feet. Groundwater provides about half of the world’s population with drinking water and nearly half of all water used to irrigate crops. It sustains rivers, lakes and wetlands during droughts.

Groundwater is a renewable resource, but it can take decades or even centuries for some aquifers to recover after they are depleted. Current understanding of this challenge is based mainly on where and how frequently people record measurements of water levels in wells.

In a newly published study, our team of data scientists, water specialists and policy experts compiled the first global-scale dataset of these levels. We analyzed millions of groundwater level measurements in 170,000 wells located in over 40 countries and mapped how groundwater levels have changed over time.

Our study has two main findings. First, we show that rapid groundwater depletion is widespread around the world and that rates of decline have accelerated in recent decades, with levels falling by 20 inches or more yearly in some locations. Second, however, our research also reveals many cases where deliberate actions halted groundwater depletion. These results show that societies are not inevitably doomed to drain their groundwater supplies, and that with timely interventions, this important resource can recover.

Portrait of a thirsty planet

Many factors determine groundwater levels, including geology, climate and land use. But groundwater levels that are dropping deeper and deeper in a particular location often signal that people are pumping it out faster than nature can replenish it.

Some of the 300 million measurements we compiled were recorded by automated measuring devices. Many others were made in the field by people around the globe. And these measurements paint a worrying picture.

They show that groundwater levels have declined since the year 2000 in far more places than they rose. In many locations, especially arid zones that are heavily farmed and irrigated, groundwater levels are falling by more than 20 inches (0.5 meters) per year. Examples include Afghanistan, Chile, China, Peninsular India, Iran, Mexico, Morocco, Saudi Arabia, Spain and the U.S. Southwest.

Our second and more concerning finding is that in about one-third of the areas where we compiled measurements, the rate of groundwater decline is accelerating. Accelerated groundwater decline is common in dry climates where large swaths of land are used for agriculture. This suggests a potential link between groundwater-fed irrigation and intensifying groundwater depletion.

What happens when groundwater is overused?

Rapid and accelerating groundwater-level declines have many harmful effects.

Drinking-water supplies from wells and springs can run dry when groundwater levels decline. People and communities who rely on those wells can lose access to what may be their sole source of accessible fresh water for drinking.

For example, wells that supply fresh water to homes are running dry in California’s San Joaquin Valley, where groundwater depletion has accelerated since the early 2000s. This problem is likely to continue and worsen unless action is taken to stabilize groundwater reserves.

Wells that run dry can also threaten crop production. Groundwater depletion has long been viewed as one of the greatest threats to global irrigated agriculture, because wells supply nearly half of the water used for irrigation globally.

In areas where groundwater typically drains to rivers, falling groundwater levels can reverse this flow and cause rivers to leak into the subsurface. This affects the river’s ecology and reduces water supplies downstream. In the U.S., leaky streams are more common where groundwater withdrawal rates are high, highlighting how groundwater pumping can directly reduce the amount of water that flows underground into nearby rivers.

Groundwater declines can also cause land surfaces to sink. Land subsidence has increased flood risks in dozens of coastal cities worldwide, including Jakarta, Tokyo, Istanbul, Mumbai, Auckland and the Tampa Bay area of Florida.

Farther from the coast, land subsidence can damage infrastructure. It poses a critical challenge in areas where groundwater levels have declined, including Tehran and Mexico City. In many cases, the main culprit is excessive groundwater pumping.

 

Finally, falling groundwater can cause seawater to move inland underground and contaminate coastal groundwater systems – a process known as seawater intrusion. When seawater intrudes, coastal aquifers can become too saline to use for drinking water without energy-intensive desalination.

How to replenish groundwater supplies

We also found places where groundwater levels are recovering. The strategies that communities used to replenish their groundwater sources included developing new alternative water supplies, such as local rivers; adopting policies to reduce demand for groundwater; and intentionally replenishing aquifers with surface water.

The town of El Dorado, Arkansas, saw its groundwater levels drop by roughly 200 feet (60 meters) from 1940 through 2000 as local industries pumped water from the aquifer. In 1999, a new policy established a pumping fee structure, giving businesses an incentive to find a new water supply. By 2005, a pipeline had been built to divert water from the Ouachita River to El Dorado. This new source reduced demand for groundwater, and groundwater levels have risen in the area since 2005.

In Bangkok, so many private wells were drilled for domestic, industrial or commercial purposes between 1980 and 2000 that groundwater pumping doubled and groundwater levels fell. Officials responded by quadrupling groundwater extraction fees between 2000 and 2006. Total groundwater pumping declined, and levels began to recover as users found other water sources.

In a valley near Tucson, Arizona, groundwater levels declined by 100 feet (30 meters) as withdrawals for irrigation increased after the 1940s. To help replenish the depleted groundwater, leaky ponds were constructed. These ponds are filled with water from the Colorado River that is moved hundreds of miles to the area via canals. As these ponds leak, they refill the depleted aquifer. Because of these leaky ponds, groundwater levels in the valley have risen by about 200 feet (60 meters) in places.

Our analysis shows how important it is to monitor groundwater levels in many locations. With groundwater levels declining in many places, communities and businesses that depend on it need accurate information about their water supplies so they can act in time to protect them.

Scott Jasechko, Associate Professor of Water Resources, University of California, Santa Barbara; Debra Perrone, Associate Professor of Environmental Studies, University of California, Santa Barbara, and Richard Taylor, Professor of Hydrogeology, UCL

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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Written by: ESA/Hubble

Published: 27 January 2024

Astronomers using the NASA/ESA Hubble Space Telescope observed the smallest exoplanet where water vapor has been detected in its atmosphere.

At only approximately twice Earth’s diameter, the planet GJ 9827d could be an example of potential planets with water-rich atmospheres elsewhere in our galaxy.

“This would be the first time that we can directly show through an atmospheric detection that these planets with water-rich atmospheres can actually exist around other stars,” said team member Björn Benneke of the Université de Montréal. “This is an important step toward determining the prevalence and diversity of atmospheres on rocky planets."

However, it remains too early to tell whether Hubble spectroscopically measured a small amount of water vapor in a puffy hydrogen-rich atmosphere, or if the planet’s atmosphere is mostly made of water, left behind after a primeval hydrogen/helium atmosphere evaporated under stellar radiation.

“Our observing programme was designed specifically with the goal of not only detecting the molecules in the planet’s atmosphere, but of actually looking specifically for water vapor. Either result would be exciting, whether water vapor is dominant or just a tiny species in a hydrogen-dominant atmosphere,” said the science paper’s lead author, Pierre-Alexis Roy of the Université de Montréal.

“Until now, we had not been able to directly detect the atmosphere of such a small planet. And we’re slowly getting into this regime now,” added Benneke. “At some point, as we study smaller planets, there must be a transition where there’s no more hydrogen on these small worlds, and they have atmospheres more like Venus (which is dominated by carbon dioxide)."

Because the planet is as hot as Venus at roughly 425 degrees Celcius, it definitely would be an inhospitable, steamy world if the atmosphere were predominantly water vapor.

At present the team is left with two possibilities. The planet is still clinging to a hydrogen-rich envelope laced with water, making it a mini-Neptune. Alternatively, it could be a warmer version of Jupiter’s moon Europa, which has twice as much water as Earth beneath its crust. “The planet GJ 9827d could be half water, half rock. And there would be a lot of water vapor on top of some smaller rocky body,” said Benneke.

If the planet has a residual water-rich atmosphere, then it must have formed farther away from its host star, where the temperature is cold and water is available in the form of ice, than its present location.

In this scenario, the planet would have then migrated closer to the star and received more radiation.

The hydrogen was then heated and escaped, or is still in the process of escaping, the planet’s weak gravity. The alternative theory is that the planet formed close to the hot star, with a trace of water in its atmosphere.

The Hubble programme observed the planet during 11 transits — events in which the planet crossed in front of its star — that were spaced out over three years. During transits, starlight is filtered through the planet’s atmosphere and carries the spectral fingerprint of water molecules.

If there are clouds on the planet, they are low enough in the atmosphere that they don’t completely hide Hubble’s view of the atmosphere, and Hubble is able to probe water vapour above the clouds.

Hubble’s discovery opens the door to studying the planet in more detail. It’s a good target for the NASA/ESA/CSA James Webb Space Telescope to do infrared spectroscopy to look for other atmospheric molecules.

GJ 9827d was discovered by NASA’s Kepler Space Telescope in 2017. It completes an orbit around a red dwarf star every 6.2 days. The star, GJ 9827, lies 97 light-years from Earth in the constellation Pisces.

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Written by: Elizabeth Larson

Published: 26 January 2024

LAKE COUNTY, Calif. — The Board of Supervisors kicked off the year by approving a contract for a new solar installation to serve the Lake County Courthouse campus.

Public Services Director Lars Ewing presented a resolution and a contract with Staten Solar Corp., totaling $2,284,131, for design, installation and commissioning of the new solar installation to the board at its Jan. 9 meeting.

The planned solar array will serve the courthouse, District Attorney’s Office and the courthouse museum, which Ewing said are all served through the same meter.

Ewing’s report explained that, over the last few years, his staff — working along with the county’s Space Use Committee and Capital Improvement Committee — has worked on a photovoltaic and electric vehicle charging station project at the courthouse campus “to implement a high-visibility clean energy project.”

He added, “The purpose of this item is to consider a resolution making findings that the project will result in energy cost savings greater than the cost of the project, as well as a contract with Staten Solar Corporation to design, build, and commission the project.

Ewing said that in September 2022 the board heard a presentation summarizing the findings of a preliminary energy audit report for county facilities.

The report identified the courthouse, as well as the District Attorney’s Office parking lot that sits behind it, as good sites for solar photovoltaic panels and electric vehicle charging stations.

Ewing said the board approved funding for the project in its fiscal year 2022-23 budget, and in October of 2022 hired Optony Inc. “to provide procurement and selection assistance as well as third-party financial and design analysis for the project.”

Optony was tasked with soliciting requests for proposals to design and construct the project. Six companies submitted proposals and San Jose-based Staten Solar Corp. was selected.

The project the board approved is a 444 kilowatt solar photovoltaic carport array at the main parking lot situated west of the District Attorney’s Office building.

Ewing said both the courthouse and District Attorney’s Office buildings are currently powered by Pacific Gas and Electric, with typical annual energy consumption and PG&E charges of approximately 870,000 kilowatt-hour and $210,000 at the courthouse, and 290,000 kilowatt-hour and $70,000 at the district attorney’s building.

The proposed solar array will produce an estimated 670,000 kilowatt-hours for the two buildings.

Ewing told the board during the Jan. 9 meeting that funding for the project was allocated in this year’s budget.

It was decided that the best project was a carport parking lot array just west of the District Attorney’s Office. “Typically you might consider a roof project,” Ewing said, but both the courthouse and DA’s Office are heavily in use and generating revenue for the county through facility space leases with AT&T, T-Mobile and Verizon for telecommunications equipment.

Having a rooftop array would make future roof repairs and general roof access very challenging, while Ewing explained in his written report that a carport array will provide an additional benefit to employees and visitors alike.

The financial analysis completed by Optony assumes a 3% assumed annual PG&E rate escalation, a 0.5% annual panel degradation rate, the county paying for operations and maintenance costs after the 10th year and the county’s receipt of a 30% investment tax credit, Ewing’s written report explained.

That analysis anticipates that the array the county is planning will offset 58% of facility use at both buildings and provide a payback period of approximately 10 years, resulting in total savings of approximately $3.27 million over the 25-year system life. “The modules are power warranted for 30 years, so the cost savings may very well exceed these figures,” Ewing’s report explained.

“Ultimately this project is intended to save us money in the long term,” Ewing told the board.

In addition, the project includes three dual-port electronic vehicle charging stations. “These stations were included in the project with the vision that the County would soon add electric vehicles to its fleet. Whether or not that occurs, the charging stations will be available on a pay-for-use basis for non-County EV’s (this potential revenue was not included in Optony’s financial analysis),” Ewing’s report explained.

The county worked with the city of Lakeport’s Community Development Department staff to evaluate the project under the California Environmental Quality Act, or CEQA. Ewing reported that the city of Lakeport has confirmed it is ministerially exempt from CEQA.

Board Chair Bruno Sabatier said he thought he would see more than three connections for electric vehicles and he wanted to be prepared for future growth. He asked if it’s easy to add more connections. Jonathan Whelan of Optony, who attended the meeting virtually, said the answer was yes, with some additional costs.

“I’m thinking 25 years from now, our parking lot will look drastically different in the vehicles that we have,” said Sabatier, adding that he would love to see them being able to prepare for expansion of charging stations.

Supervisor Moke Simon agreed, suggesting they could at least put conduit in the ground so the system is expandable.

Ewing noted during the discussion that the EV charging stations will eliminate some regular parking stalls in the DA’s Office parking lot. “I think the reward is better than the risk.”

Simon also asked about battery backup in the future. Whelan said the project originally was designed with battery storage as an alternative. While it added additional savings, it was not enough to cover the additional cost.

However, Whelan said that will change in the coming years, and the system can be retrofitted with a battery energy storage system.

Possible locations for battery storage included an equipment pad on the north side of the DA’s Office as well as inside the DA’s Office sally port.

The supervisors unanimously approved both the resolution to authorize the contract and the agreement.

Ewing’s report said that it’s expected that the project will be commissioned by the fall. Once the contract is in effect, there will be a detailed construction schedule and schematic design.

Lake County has been doing major solar projects since 2007, when it began work on a 3 megawatts array that was credited as being the largest solar-energy system on county property in California at the time.

Email Elizabeth Larson at This email address is being protected from spambots. You need JavaScript enabled to view it.. Follow her on Twitter, @ERLarson, or Lake County News, @LakeCoNews.