Monitor groundwater along river corridors

Study uses remote sensing to monitor groundwater along river corridors in  the Southwest - Naveen Bharat

Spend time in any of the world’s great forests and you’ll start seeing the trees as immense pillars holding the heavens aloft while firmly anchored in the earth. It’s as much fact as sentiment. Trees really do link the ground to the sky by exchanging energy and matter between the soil and the atmosphere. Researchers believe that understanding this connection could provide both a wealth of scientific insight into ecosystems and practical applications that address challenges such as water resource conservation and management.

A recent study led by UC Santa Barbara’s Marc Mayes investigates how patterns in tree water loss to the atmosphere, tracked with satellite imagery, relates to groundwater supplies. The results validate at landscape-wide scales ideas that scientists have proposed based on decades of research in labs and greenhouses. What’s more, the techniques lend themselves to an accurate, efficient way of monitoring groundwater resources over large areas. The findings appear in the journal Hydrological Processes.

For all their diversity, most plants have a very simple game plan. Using energy from sunlight, they combine water from the ground with carbon dioxide from the air to produce sugars and oxygen. During photosynthesis, plants open small pores in their leaves to take in CO2, which also allows water to escape. This process of water loss is called evapotranspiration — short for soil evaporation and plant transpiration — and it’s essentially a transaction cost of transporting the ingredients for photosynthesis to the leaves where the process occurs.

Just like evaporating sweat cools down our own bodies, the evapotranspiration from the trees cools down the forest. With the proper understanding and technology, scientists can use thermal image data from satellites as well as manned and unmanned aircraft to understand the relationship between plants and groundwater: cooler temperatures correlate with more evapotranspiration.

“The core hypothesis of this paper is that you can use relationships between plant water use [as] measured by [satellite] image data, and climate data including air temperature and rainfall, to gauge the availability of, and changes in, groundwater resources,” said Mayes, an Earth scientist and remote sensing expert based at the university’s Earth Research Institute (ERI).

Mayes and his colleagues focused on the flora of dryland rivers — those in deserts and Mediterranean climates. Throughout these regions, many plants have evolved adaptations that minimize water loss, like slow growth, water retention or boom-bust lifecycles. However, plants that dominate river channels — species like sycamore, cottonwood and willows — evolved to take advantage of the surplus groundwater the habitat offers relative to the surrounding landscape.

“Rather than slowing down its water use when water becomes scarce, this vegetation will basically drink itself to death,” Mayes said. This makes it a good window into conditions below the surface.

The team used satellite-based thermal imaging to look at temperatures across the San Pedro River corridor in southern Arizona. On cloud-free days the satellites can gather data on surface temperatures at high resolution over large areas of land. By comparing the temperatures along the river to those in nearby, more sparsely vegetated areas, the researchers were able to determine the extent of evapotranspiration along different parts of the river at different times. They found that it correlated with air temperature in water-rich environments and with rainfall in water-scarce environments.

The findings support recent advances in our understanding of plant water use. The hotter and drier the air, the stronger it pulls water from the leaves, and the more water the plant uses. Consequently, Mayes and his colleagues expected to see evapotranspiration vary with air temperature as long as the stream has abundant groundwater for the plants to draw on.

On the other hand, where groundwater is scarce, plants will close the openings on their leaves to avoid water loss; it’s more important to avoid drying out than to take advantage of the extra sunshine on a warm day. As a result, evapotranspiration will correlate much more strongly with rainfall and streamflow, which increases the supply of water to trees through their roots.

Scientists had demonstrated the predictable effect of evapotranspiration in lowering surface temperatures in lab and small field experiments. However, this is the first study to demonstrate its impact over large areas. The technology that made this possible has matured only within the past five years.

“This remote sensing method shows great promise for identifying the relevant climatic versus other controls on tree growth and health, even within narrow bands of vegetation along rivers,” said coauthor Michael Singer, a researcher at ERI and lead investigator on the project that funded Mayes’ work.

In fact, these ecosystems are vitally important to the southwestern U.S. “Despite taking up about 2% of the landscape, over 90% of the biodiversity in the Southwest relies on these ecosystems,” said coauthor Pamela Nagler, a research scientist at the U.S. Geological Survey’s Southwest Biological Science Center.

The same techniques used in the paper could be applied to the perennial challenge of groundwater monitoring. In fact, this idea helped motivate the study in the first place. “It’s very hard to monitor groundwater availability and change[s] in groundwater resources at the really local scales that matter,” Mayes said. “We’re talking about farmers’ fields or river corridors downstream of new housing developments.”

Monitoring wells are effective, but provide information only for one point on the map. What’s more, they are expensive to drill and maintain. Flux towers can measure the exchange of gasses between the surface and the atmosphere, including water vapor. But they have similar drawbacks to wells in terms of cost and scale. Scientists and stakeholders want reliable, cost-effective methods to monitor aquifers that provide wide coverage at the same time as high resolution. It’s a tall order.

While it may not be quite as precise as a well, remote thermal imaging from aircraft and satellites can check off all of these boxes. It offers wide coverage and high resolution using existing infrastructure. And although it works only along stream corridors, “an inordinate amount of agricultural land and human settlements in dry places ends up being where the water is, along stream paths,” Mayes said.

The idea is to look for shifts in the relationships of evapotranspiration to climate variables over time. These changes will signal a switch between water-rich and water-poor conditions. “Detecting that signal over large areas could be a valuable early warning sign of depleting groundwater resources,” Mayes said. The technique could inform monitoring and pragmatic decision-making on groundwater use.

This study is part of a larger Department of Defense (DOD) project aimed at understanding how vulnerable riverine habitats are to droughts on DOD bases in dryland regions of the U.S. “We are using multiple methods to understand when and why these plants become stressed due to lack of water,” said Singer, the project’s lead scientist. “[We hope] this new knowledge can support the management of these sensitive ecological biomes, particularly on military bases in dryland regions, where these pristine habitats support numerous threatened and endangered species.”

Mayes added, “What’s coming down the pipe is a whole ensemble of work looking at ecosystem responses to water scarcity and water stress across space and time that informs ways we both understand ecosystem response and also improve the monitoring.”make a difference: sponsored opportunity


Story Source:

Materials provided by University of California – Santa Barbara. Original written by Harrison Tasoff. Note: Content may be edited for style and length.


Journal Reference:

  1. Marc Mayes, Kelly K. Caylor, Michael Bliss Singer, John C. Stella, Dar Roberts, Pamela Nagler. Climate sensitivity of water use by riparian woodlands at landscape scalesHydrological Processes, 2020; 34 (25): 4884 DOI: 10.1002/hyp.13942

FOR MORE INFORMATION: University of California – Santa Barbara. “Monitor groundwater along river corridors.” ScienceDaily. ScienceDaily, 16 December 2020. <www.sciencedaily.com/releases/2020/12/201216134651.htm>.

Oregon’s Western Cascades watershed to experience larger, more frequent fires

Study: Oregon's Western Cascades watershed to experience larger, more  frequent fires

The Clackamas Basin rarely experiences the intense fire activity that burned in the watershed during the Labor Day fires, but new research out of Portland State University shows that wildfires like the Riverside Fire, which grew to 138,000 acres within days, could become more common under a warming climate, even under non-extreme wind conditions.

The study found that wildfire hazard in the Clackamas Basin, which is the second largest source of drinking water for the Portland metro area, will likely increase by mid-century. Projected changes in temperature and relative humidity are expected to lead to longer fire seasons and more severe fire weather in Oregon’s Western Cascade mountains, which in turn will result in larger, more frequent fires.

“Because of shifts in climate, the scenarios that would create extreme fire events all become a little more plausible,” said Andy McEvoy, the study’s lead author and a graduate student in environmental science and management. “There will be that many more days under which those components of a fire — ignition, weather and fuel — can align in a terrible way.”

The group of researchers simulated four climate scenarios from 2040-2069, representing a range of plausible changes in temperature and humidity.

The simulations showed that the fire season increased from as little as eight days to as much as 32 days. The projected annual average area burned increased significantly by 50% under the least impactful scenario (the coolest and wettest of the four) and as much as 540% under the most extreme scenario (the hottest and driest of the four).

“We don’t make the case that one future is more likely than the other, but it helps bracket the plausible outcomes for planning purposes,” said McEvoy, who works as a research fellow in the U.S. Forest Service’s Pacific Northwest Research Station. “The future is very uncertain and if land and resource managers plan just for the average case, their plans are not going to be robust in the face of those worst-case scenarios.”

The researchers, who worked closely with the Clackamas River Water Providers and the Clackamas County Water and Environment Services, said the findings provide regional managers and planners with a tool to develop climate adaptation and risk mitigation strategies. Given the wide range of plausible future wildfire hazards, robust adaptation plans will be ones that maintain essential ecosystem services across the broadest range of scenarios by balancing land use management, fire suppression, and community preparedness strategies.

These efforts could range from designing and testing the effectiveness of fuel breaks — breaks in vegetation that can help firefighters control the spread of fire and protect homes and resources — to identifying susceptible communities and planning evacuations in the event of future extreme wildfires. In those cases, like the Riverside Fire, fuel breaks would not be successful and the only sensible strategy would be timely, safe evacuations.

“They’re planning for an uncertain future,” McEvoy said. “They have to plan using all available tools and adapt to events as they occur.”make a difference: sponsored opportunity


Story Source:

Materials provided by Portland State University. Original written by Cristina Rojas. Note: Content may be edited for style and length.


Journal Reference:

  1. Andy McEvoy, Max Nielsen-Pincus, Andrés Holz, Arielle J. Catalano, Kelly E. Gleason. Projected Impact of Mid-21st Century Climate Change on Wildfire Hazard in a Major Urban Watershed outside Portland, Oregon USAFire, 2020; 3 (4): 70 DOI: 10.3390/fire3040070

Portland State University. “Oregon’s Western Cascades watershed to experience larger, more frequent fires.” ScienceDaily. ScienceDaily, 14 December 2020. <www.sciencedaily.com/releases/2020/12/201214123447.htm>.

‘Sparkling’ clean water from nanodiamond-embedded membrane filters

Sparkling' clean water from nanodiamond-embedded membrane filters |  EurekAlert! Science News

Although most of the planet is covered by water, only a fraction of it is clean enough for humans to use. Therefore, it is important to recycle this resource whenever possible. Current purification techniques cannot adequately handle the very hot wastewater generated by some industries. But now, researchers reporting in ACS Applied Materials & Interfaces have embedded amine-enhanced nanodiamond particles into membranes to address this challenge.

Some oil recovery methods and other industrial processes result in hot wastewater, which requires energy-intensive cooling before it can be purified through traditional reverse osmosis membranes. After purification, the water then needs to be heated before it can be re-used. At such high temperatures, traditional reverse osmosis membranes filter slowly, allowing more salts, solids and other contaminants to get through. Researchers have embedded extremely tiny nanodiamonds — carbon spheres produced by explosions in small, closed containers without oxygen present — onto these membranes in previous studies. Although the membranes effectively and quickly filtered large volumes of water and can protect against fouling, they were not tested with very hot samples. To optimize the membranes for use with hot wastewater, Khorshidi, Sadrzadeh and colleagues wanted to modify the nanodiamond spheres and embed them in a new way.

The team attached amines to nanodiamonds and bathed them in an ethyl acetate solution to prevent the spheres from clumping. Then, a monomer was added that reacted with the amines to create chemical links to the traditional membrane base. Synergistic effects of the amine links and the ethyl acetate treatment resulted in thicker, more temperature-stable membranes, contributing to improvements in their performance. By increasing the amount of amine-enhanced nanodiamonds in the membrane, the researchers obtained higher filtration rates with a greater proportion of impurities being removed, even after 9 hours at 167 F, when compared to membranes without nanodiamonds. The new method produced membranes that could more effectively treat wastewater at high temperatures, the researchers say.make a difference: sponsored opportunity


Story Source:

Materials provided by American Chemical SocietyNote: Content may be edited for style and length.


Journal Reference:

  1. Pooria Karami, Behnam Khorshidi, Laleh Shamaei, Eric Beaulieu, João B. P. Soares, Mohtada Sadrzadeh. Nanodiamond-Enabled Thin-Film Nanocomposite Polyamide Membranes for High-Temperature Water TreatmentACS Applied Materials & Interfaces, 2020; 12 (47): 53274 DOI: 10.1021/acsami.0c15194

FOR MORE INFORMATION: American Chemical Society. “‘Sparkling’ clean water from nanodiamond-embedded membrane filters.” ScienceDaily. ScienceDaily, 9 December 2020. <www.sciencedaily.com/releases/2020/12/201209124933.htm>.

Low oxygen levels in lakes and reservoirs may accelerate global change

Low oxygen levels in lakes and reservoirs may accelerate global change |  EurekAlert! Science News

Because of land use and climate change, lakes and reservoirs globally are seeing large decreases in oxygen concentrations in their bottom waters. It is well-documented that low oxygen levels have detrimental effects on fish and water quality, but little is known about how these conditions will affect the concentration of carbon dioxide and methane in freshwaters.

Carbon dioxide and methane are the primary forms of carbon that can be found in the Earth’s atmosphere. Both of these gases are partially responsible for the greenhouse effect, a process that increases global air temperatures. Methane is 34 times more potent of a greenhouse gas than carbon dioxide, so knowing how low oxygen levels within lakes and reservoirs affect both carbon dioxide and methane could have important implications for global warming.

Until now, researchers did not have any empirical data from the whole-ecosystem scale to definitively say how changing oxygen can affect these two greenhouse gases.

“We found that low oxygen levels increased methane concentrations by 15 to 800 times at the whole-ecosystem scale,” said Alexandria Hounshell, a postdoctoral researcher in the Department of Biological Sciences in the College of Science. “Our work shows that low oxygen levels in the bottom waters of lakes and reservoirs will likely increase the global warming potential of these ecosystems by about an order of magnitude.”

Virginia Tech researchers just published these findings in a high-impact paper in Limnology and Oceanography Letters.

To determine a correlation between oxygen and methane concentrations, researchers honed in on two reservoirs outside of Roanoke. In collaboration with the Western Virginia Water Authority, the research team operated an oxygenation system in Falling Creek Reservoir, which pumps oxygen into the bottom waters and allows researchers to study oxygen concentrations on a whole-ecosystem scale. By also monitoring Beaverdam Reservoir, an upstream reservoir without an oxygenation system, they were able to compare greenhouse gas concentrations in the bottom waters of both reservoirs. They ran the experiment over three years to see how consistent their findings were over time.

“Methane levels were much higher when there was no oxygen in the bottom waters of these reservoirs; whereas the carbon dioxide levels were the same, regardless of oxygen levels,” said Cayelan Carey, associate professor of biological sciences and affiliated faculty member of the Global Change Center. “With low oxygen levels, our work shows that you’ll get higher production of methane, which leads to more global warming in the future.”

This study was one of the first to experimentally test at the whole ecosystem-scale how different oxygen levels affect greenhouse gases. Logistically, it is extremely challenging to manipulate entire ecosystems due to their complexity and many moving parts. Even though scientists can use computer modelling and lab experiments, nothing is as definitive as the real thing.

“We were able to do a substitution of space for time because we have these two reservoirs that we can manipulate and contrast with one another to see what the future may look like, as lower bottom water oxygen levels become more common. We can say with high certainty that we are going to see these lakes become bigger methane emitters as oxygen levels decrease,” said Carey.

According to Hounshell, the strength of their results lie in the study’s expanse over multiple years. Despite having a range of meteorological conditions over the three years, the study affirmed that much higher methane concentrations in low oxygen conditions happen consistently every year, no matter the air temperature.

Ultimately, this study is crucial for how researchers, and the general public, think about how freshwater ecosystems produce greenhouse gases in the future. With low oxygen concentrations increasing in lakes and reservoirs across the world, these ecosystems will produce higher concentrations of methane in the future, leading to more global warming.

Of course, these ecological changes are not just happening in the Roanoke region. Around the globe, a number of studies have pointed to changing carbon cycling in terrestrial and marine ecosystems. However, this study is one of the few to address this phenomenon in lakes and reservoirs, which are often neglected in carbon budgets. This study will fill in these knowledge gaps and shine a spotlight on what we can do as citizens to solve this problem.

This study suggests that keeping lakes from experiencing low oxygen concentrations in the first place could further prevent them from hitting the tipping point, when they start to become large methane producers. Small decisions can add up. For example, decreasing runoff into lakes and reservoirs can prevent the depletion of oxygen in their bottom waters. “Don’t put a ton of fertilizer on your lawn, and be really strategic about how much fertilizer you use and how you use it,” said Hounshell.

And greenhouse gases are just a small part of the bigger picture of how reservoirs function in the global carbon cycle. Currently, the research team is conducting follow-up oxygen manipulation studies to elucidate other components that contribute to ecosystem change. They will continue to monitor oxygen manipulations in the two Roanoke reservoirs to see how the reservoir can affect the ecosystem for the long haul.

This project was funded by the Virginia Tech Institute for Critical Technology and Applied Science, the Fralin Life Sciences Institute at Virginia Tech, and by National Science Foundation grant DEB-1753639.make a difference: sponsored opportunity


Story Source:

Materials provided by Virginia TechNote: Content may be edited for style and length.


Journal Reference:

  1. Alexandria G. Hounshell, Ryan P. McClure, Mary E. Lofton, Cayelan C. Carey. Whole‐ecosystem oxygenation experiments reveal substantially greater hypolimnetic methane concentrations in reservoirs during anoxiaLimnology and Oceanography Letters, 2020; DOI: 10.1002/lol2.10173

FOR MORE INFORMATION: Virginia Tech. “Low oxygen levels in lakes and reservoirs may accelerate global change.” ScienceDaily. ScienceDaily, 10 December 2020. <www.sciencedaily.com/releases/2020/12/201210120349.htm>.

Several U.S. populations and regions exposed to high arsenic concentrations in drinking water

Columbia Researchers Warn: Several U.S. Populations and Regions Exposed to High  Arsenic Concentrations in Drinking Water

A new national study of public water systems found that arsenic levels were not uniform across the U.S., even after implementation of the latest national regulatory standard. In the first study to assess differences in public drinking water arsenic exposures by geographic subgroups, researchers at Columbia University Mailman School of Public Health confirmed there are inequalities in drinking water arsenic exposure across certain sociodemographic subgroups and over time. Community water systems reliant on groundwater, serving smaller populations located in the Southwest, and Hispanic communities were more likely to continue exceeding the national maximum containment level, raising environmental justice concerns. The findings are published online in Environmental Health Perspectives.

“This research has important implications for public health efforts aimed at reducing arsenic exposure levels, and for advancing environmental justice,” said Anne Nigra, PhD, postdoctoral research fellow in environmental health sciences, and first author. “Systematic studies of inequalities in public drinking water exposures have been lacking until now. These findings identify communities in immediate need of additional protective public health measures.”

‘Our objective was to identify subgroups whose public water arsenic concentrations remained above 10 µg/L after the new maximum arsenic contaminant levels were implemented and, therefore, at disproportionate risk of arsenic-related adverse health outcomes such as cardiovascular disease, related cancers, and adverse birth outcomes,” said Ana Navas-Acien, PhD, Professor of Environmental Health Sciences and senior author.

Arsenic is a highly toxic human carcinogen and water contaminant present in many aquifers in the United States. Earlier research by the Columbia research team showed that reducing the MCL from 50 to 10 µg/L prevented an estimated 200-900 cancer cases per year.

The researchers compared community water system arsenic concentrations during (2006-2008) versus after (2009-2011) the initial monitoring period for compliance with EPA’s 10 µg/L arsenic maximum contaminant level (MCL). They estimated three-year average arsenic concentrations for 36,406 local water systems and 2,740 counties and compared differences in means and quantiles of water arsenic between both three-year periods for U.S. regions and sociodemographic subgroups.

Analyses were based on data from two of the largest EPA databases of public water available. Using arsenic monitoring data from the Third Six Year Review period (2006-2011), the researchers studied approximately 13 million analytical records from 139,000 public water systems serving 290 million people annually. Included were data from 46 states, Washington D.C., the Navajo Nation, and American Indian tribes representing 95 percent of all public water systems and 92 percent of the total population served by public water systems nationally.

Regional Differences

For 2006-2008 to 2009-2011, the average community water system arsenic concentrations declined by 10 percent nationwide, by 11.4 percent for the Southwest, and by 37 percent for New England, respectively. Despite the decline in arsenic concentrations, public drinking water arsenic concentrations remained higher for several sociodemographic subgroups — Hispanic communities, the Southwestern U.S, the Pacific Northwest, and the Central Midwest., in particular. Likewise, communities with smaller populations and reliant on groundwater were more likely to have high arsenic levels.

The percent of community water systems with average concentrations arsenic above the 10 µg/L MCL was 2.3% in 2009-2011 vs. 3.2% in 2006-2008. Community water systems that were not compliant with the arsenic MCL were more likely in the Southwest (61 percent), served by groundwater (95 percent), serving smaller populations (an average of 1,102 persons), and serving Hispanic communities (38 percent).

Nigra and Navas-Acien say that estimating public drinking water arsenic exposure for sociodemographic and geographic subgroups is critical for evaluating whether inequalities in arsenic exposure and compliance with the maximum contaminant levels persist across the U.S, to inform future national- and state-level arsenic regulatory efforts, and to investigate whether inequalities in exposure by subgroup contribute to disparities in arsenic-related disease. “Our findings will help address environmental justice concerns and inform public health interventions and regulatory action needed to eliminate exposure inequalities.”

“We urge continued state and federal funding for infrastructure and technical assistance support for small public water systems in order to reduce inequalities and further protect numerous communities in the U.S. affected by elevated drinking water arsenic exposure,” said Nigra.make a difference: sponsored opportunity


Story Source:

Materials provided by Columbia University’s Mailman School of Public HealthNote: Content may be edited for style and length.


Journal Reference:

  1. Anne E. Nigra, Qixuan Chen, Steven N. Chillrud, Lili Wang, David Harvey, Brian Mailloux, Pam Factor-Litvak, Ana Navas-Acien. Inequalities in Public Water Arsenic Concentrations in Counties and Community Water Systems across the United States, 2006–2011Environmental Health Perspectives, 2020; 128 (12): 127001 DOI: 10.1289/EHP7313

FOR MORE INFORMATION: Columbia University’s Mailman School of Public Health. “Several U.S. populations and regions exposed to high arsenic concentrations in drinking water.” ScienceDaily. ScienceDaily, 9 December 2020. <www.sciencedaily.com/releases/2020/12/201209094243.htm>.

Big data offers promise of better groundwater management in California

Big data offers promise of better groundwater management in California |  Newsroom - McGill University

To ensure that California’s groundwater is sustainably managed in the future and over the long-term, current state definitions of what constitutes groundwater may need to be revised, according to research published this week in PNAS. A McGill University-led research team has analyzed big data of more than 200,000 groundwater samples taken from across the state and found that there are problems with the guidelines used for groundwater management. Known as the ‘Base of Fresh Water’, the guidelines are close to fifty years old and don’t reflect current uses, knowledge, concerns or technologies related to managing groundwater in this coastal state with a multi-billion-dollar agricultural industry.

The research shows that existing groundwater wells already penetrate and encroach upon the bases of fresh water that are used to define basin bottoms. In addition, brackish waters exist within current groundwater basins, and fresh water exists outside delineated groundwater basins. Brackish water, which was once deemed unusable, can now be used, thanks to technological advances. Finally, there are concerns about regulating groundwater on the basis of its quality rather than its usage, as is currently the case, since this provides a loophole for potential groundwater users who could drill deeper and skirt existing restrictions on freshwater pumping.

Together, these findings suggest that groundwater may already be poorly safeguarded in some places and that the ‘Base of Fresh Water’ concept may need to be reconsidered as a means to define and sustainably manage groundwater in future.

Need for up-to-date information to manage a critical resource

“It is challenging for groundwater sustainability agencies to manage groundwater because this critical resource is not being sufficiently monitored,” says Mary Kang, an Assistant Professor in McGill University’s Department of Civil Engineering and the lead author on the study. An expert on groundwater issues, she has studied the topic in California since 2014. “The base of fresh water was historically set to protect high quality groundwater from oil and gas development. And we find that there is a mismatch between this base of fresh water and what the water quality data shows.”

“One component to managing groundwater sustainably is evaluating the physical resource within the context of its users,” says Debra Perrone co-author of the study and Assistant Professor in UC Santa Barbara’s Environmental Studies Program. “We evaluate the link between groundwater quality, particularly salinity, and groundwater users. We show that the current approach used to manage deep groundwater in some places may risk overlooking the complex realities pertaining to both groundwater salinity and groundwater users. For example, the data suggest that people are constructing groundwater wells deeper than the base of fresh water in some areas.”

In 2014, in response to repeated droughts, the state passed the Sustainable Groundwater Management Act (SGMA) to regulate groundwater for the first time in California’s history. However, the effectiveness of this legislation is yet to be determined, as it relies upon administrative definitions of groundwater that are based on the extent of fresh water to define a vertical or three-dimensional groundwater basin for managing water.

“The Sustainable Groundwater Management Act currently only applies to fresh groundwater basins since administrative definitions of groundwater originated decades ago when it was economically infeasible to treat and distribute ‘unusable’ brackish or saline groundwater,” says co-author Melissa Rohde, a scientist with The Nature Conservancy of California. Rohde is currently providing scientific support to advance the successful implementation of SGMA. “With technological advances, brackish water is now usable and increasingly desirable with declining access to fresh water. By excluding brackish groundwater from sustainable groundwater management, we run the risk of undermining SGMA and overexploiting this important public resource.”make a difference: sponsored opportunity


Story Source:

Materials provided by McGill UniversityNote: Content may be edited for style and length.


Journal Reference:

  1. Mary Kang, Debra Perrone, Ziming Wang, Scott Jasechko, Melissa M. Rohde. Base of fresh water, groundwater salinity, and well distribution across CaliforniaProceedings of the National Academy of Sciences, 2020; 202015784 DOI: 10.1073/pnas.2015784117

FOR MORE INFORMATION: McGill University. “Big data offers promise of better groundwater management in California: Analysis of 200,000 groundwater samples reveals major mismatch in California groundwater data.” ScienceDaily. ScienceDaily, 9 December 2020. <www.sciencedaily.com/releases/2020/12/201209170704.htm>.

New study allows regional prediction of uranium in groundwater

Landforms from Groundwater Erosion and Deposition ( Read ) | Earth Science  | CK-12 Foundation

Lurking in sediments and surrounding the precious groundwater beneath our feet is a dangerous toxin: uranium. Scientists have long known this and tested for it. But now Stanford researchers have identified the trigger that causes naturally occurring uranium to dislodge from sediments and seep into groundwater, pointing to a solution for managing the toxin before it becomes a problem.

In a new regional model that combines aquifer information with soil properties for predicting groundwater quality, the researchers pinpointed the factors associated with uranium contamination. The research, published in Environmental Science & Technology Dec. 8, indicates that calcium concentrations and soil alkalinity are key determining factors of uranium groundwater contamination in California’s Central Valley. The findings will be especially important as water managers plan for a future with more people and less water available from snowpack in a warming world.

Uranium is among the top three harmful, naturally occurring groundwater contaminants in the Central Valley, along with arsenic and chromium. The radioactive, metallic element becomes dangerous when consumed in high quantities, causing kidney damage and increased risk of cancer. It is prevalent within the Central Valley’s San Joaquin Valley, and also occurs naturally in semi-arid and arid environments worldwide.

Researchers focused on locations in the Central Valley aquifers where groundwater uranium concentrations have been observed to exceed the drinking water standard of 30 micrograms of uranium per liter.

“Every aquifer has one or more of these natural contaminants. The question is whether they sit benignly in the sediments or really cause problems by getting into the groundwater,” said co-author Scott Fendorf, the Huffington Family Professor in Earth system science at the School of Earth, Energy & Environmental Sciences (Stanford Earth). “Water managers can use our findings to forecast solutions before the problems are manifested.”

The study focuses on the chemical impacts of groundwater recharge, which is the process of rainfall seeping into soils and moving down into underlying aquifers. As rainwater seeps downward, its chemistry changes as it interacts with the ground environment. Pumping the water back out also influences the dynamics of the aquifer, which can change the chemistry of the system and how elements such as uranium are partitioned between the solids (sediments) and water. If the water picks up more calcium during its travels and also becomes more alkaline, it can attract uranium and contaminate aquifers, the researchers found.

“Our work shows that it’s not just properties of the aquifer that are impacting uranium, but factors such as clay content and pH of the soil that served as important predictors of groundwater uranium concentrations,” said lead study author Alandra Lopez, a PhD student in Earth system science. “It highlights the importance of including data about soil properties when generating aquifer vulnerability maps for a naturally occurring contaminant like uranium.”

The good news: the researchers estimate that the factors introducing this process of uranium loosening from sediments into groundwater mainly occur within the top six feet of the soil, suggesting an easy fix could involve bypassing that area.

“If you’re going to manage aquifer recharge, which will be increasingly needed with climate change, be careful about having the water infiltrate through the soil where calcium and alkalinity are often highest. These management scenarios are being considered right now,” said Fendorf, who is also a senior fellow at the Stanford Woods Institute for the Environment.

The team says their methodology offers water managers an easy way to predict major influences on groundwater uranium concentrations at scale.

“We’re trying to tell everybody that you need to think about this ahead of time, because that’s when you can manage around the problem,” Fendorf said. “It’s a kind of forward prediction versus hindsight reaction — once you measure uranium in the water, your problem is already at hand and it’s much more expensive to fix.”

This research was funded by the Water Foundation, a US National Science Foundation Graduate Research Fellowship and partly supported by the US Department of Energy, Office of Biological and Environmental Research, Subsurface Biogeochemistry Program (SBR).make a difference: sponsored opportunity


Story Source:

Materials provided by Stanford University. Original written by Danielle Torrent Tucker. Note: Content may be edited for style and length.


Journal Reference:

  1. Alandra M. Lopez, Arden Wells, and Scott Fendorf. Soil and Aquifer Properties Combine as Predictors of Groundwater Uranium Concentrations within the Central Valley, CaliforniaEnvironmental Science & Technology, 2020 DOI: 10.1021/acs.est.0c05591

FOR MORE INFORMATION: Stanford University. “New study allows regional prediction of uranium in groundwater.” ScienceDaily. ScienceDaily, 8 December 2020. <www.sciencedaily.com/releases/2020/12/201208111432.htm>.

Central Europe: Dry Aprils pave the way for summer droughts

Central Europe: Dry Aprils pave the way for summer droughts |  PreventionWeb.net

In the past 20 years, Central Europe has experienced six summer heat waves and droughts. Until now, however, it was unclear what factors led to these extreme events. Researchers from two Helmholtz Centres (AWI & UFZ) have now discovered that in Central Europe, temperature and precipitation patterns in April play a vital role in determining whether or not the soils are drier than average in the following summer. If the April is too warm, with little precipitation, a large proportion of the moisture stored in the soil evaporates, making a summer drought more likely. The team has also identified one of the reasons for the repeated dry Aprils and the correspondingly increased risk of drought. Decreasing temperature differences between the Arctic and the middle latitudes lead to a shift in the jet stream and the formation of a blocking high-pressure system over the North Sea and parts of Germany. This in turn means that the April weather in Central Europe is getting much too warm and dry, as the researchers report in a study released today in the Nature Partner Journals npj Climate and Atmospheric Science.

Monica Ionita, a climatologist and expert on weather forecasting at the Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research (AWI), can still remember it clearly: in late April 2018, it was so hot in Bremen that she put a paddling pool in the garden for her daughter, although it should have been much too early to splash around outdoors. She now knows that the spring heat wave at the time provided the impetus for the following summer being one of the driest in the history of Central Europe.

“Since the turn of the century, Central Europe has experienced repeated summer heat waves and droughts, which have caused damage amounting to millions of Euros. To date, attempts to correctly predict such extreme events have been unsuccessful because the influence of the spring has been underestimated. That is why we decided to closely investigate the links between the weather in spring and that in the subsequent summer — for the entire period for which sufficient records are available. In other words, the last 140 years,” the expert reports.

April’s pivotal role: Lack of rain coupled with heat causes soils to dry out

For the analysis, Monica Ionita and her colleagues employed climate (and hydrologic) model outputs as well as statistical methods that the AWI researchers have developed; and had already successfully applied in long-term forecasts of river water levels. The findings show: in the last 14 years, the temperature and precipitation trends in April have changed fundamentally. “While there was little change in the months of March and May in the period 2007 to 2020, April was on average 3 degrees Celsius warmer compared to the reference period 1961 to 2000. In extreme years, like 2018, it was so warm in April that the snow that had fallen in winter virtually evaporated before it had the chance to drain into the soil in the form of meltwater. Furthermore, since 2007, in most regions of Central Europe there has only been half as much rain as in the reference period,” Ionita explains.

In the past 14 years, the absence of precipitation has only been one of the problems: “Rising April temperatures have led to the moisture stored in the soil evaporating. As a result, in spring there was already a marked lack of moisture in the soils of Central Europe, especially in Germany. As a rule, this deficit couldn’t be compensated for in the summer. In other words: the summer drought in the soils was pre-programmed back in April,” adds Rohini Kumar, a hydrologist at the Helmholtz Centre for Environmental Research (UFZ) in Leipzig and co-author of the new study.

The causes of dry springs in Central Europe

But which weather conditions over Central Europe cause the repeated record-high temperatures and dry spells in April? “Our analysis shows that a blocking high-pressure system formed over the North Sea and parts of Germany in that period, and this diverted the jet stream northwards, resulting in spells of sunny and dry weather in Central Europe lasting up to two weeks,” explains Ionita. There was also a phase with similarly low precipitation in April in the period from 1881 to 1895. But at the time it wasn’t as warm, which meant that less moisture evaporated from the soil and there weren’t the long-term effects that we’re seeing today. “The serious consequences of these spring dry spells are largely due to the rising air temperatures,” comments Ionita.

We can’t yet say whether blocking high-pressure systems will determine the April weather in Central Europe in the future, since the climate is subject to natural fluctuations. But in their study, the scientists were able to identify one important driver: “One reason for the formation of stable high-pressure areas is the decreasing temperature differences between the Arctic and the middle latitudes in spring. Under these conditions, the jet stream that controls the weather in Central Europe follows a zigzagging course, allowing the high-pressure system to settle over the North Sea,” Ionita adds.

According to climate scenarios, these initial conditions will also occur in the future. However, high-pressure systems will form less frequently (be less likely to form) if we succeed in achieving the Paris climate goals and limit global warming to 1.5 degrees Celsius by 2100. “If temperature increases exceed this goal, it is highly likely that such high-pressure areas will form. In Central Europe, the month of April will continue to be warmer and drier than it was 20-30 years ago, thus paving the way for large-scale water shortages and arid soils all summer long,” warns the AWI researcher.

“Such a development would have major effects on the soils’ water balance and their associated ecosystem services,” states Kumar, adding: “In recent years, we’ve seen a series of summer droughts throughout Central Europe — with severe consequences in terms of plant productivity and low water-levels in rivers. Understanding the conditions under which such dry periods occur is vital to implement precautionary and preventive measures in time.”make a difference: sponsored opportunity


Story Source:

Materials provided by Alfred Wegener Institute, Helmholtz Centre for Polar and Marine ResearchNote: Content may be edited for style and length.


Journal Reference:

  1. M. Ionita, V. Nagavciuc, R. Kumar, O. Rakovec. On the curious case of the recent decade, mid-spring precipitation deficit in central Europenpj Climate and Atmospheric Science, 2020; 3 (1) DOI: 10.1038/s41612-020-00153-8

FOR MORE INFORMATION: Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research. “Central Europe: Dry Aprils pave the way for summer droughts: Researchers identify the causes of dry springs and describe their long-term consequences.” ScienceDaily. ScienceDaily, 7 December 2020. <www.sciencedaily.com/releases/2020/12/201207112316.htm>.

Satellite-tagged bottles show promise for tracking plastic litter through rivers

Satellite-tagged bottles show promise for tracking plastic litter through  rivers

A new study demonstrates the potential for plastic bottles tagged with tracking devices to deepen our understanding of how plastic pollution moves through rivers. Emily Duncan of the University of Exeter, U.K., and colleagues present this research in the open-access journal PLOS ONE on Dec 2, 2020.

Plastic pollution threatens natural ecosystems and human health worldwide. Previous research suggests that rivers transport up to 80 percent of the plastic pollution found in oceans. However, while ocean modeling and tracking technology have revealed detailed insights into how plastic litter moves and accumulates within oceans, river transport of plastic pollution remains poorly understood.

To help address this knowledge gap, Duncan and colleagues developed a new, low-cost, open-source tracking method that uses reclaimed 500 mL plastic bottles to house custom-designed electronics, allowing the bottles to be tracked via GPS cellular networks and satellite technology. These “bottle tags” mimic plastic beverage bottles, in the hopes that they realistically replicate the path of plastic pollution down a river.

As part of the National Geographic Sea to Source Ganges Expedition, the researchers released 25 bottle tags at various sites along the Ganges River. They successfully tracked several of them through the river and into the Bay of Bengal. They also released three bottles directly into the Bay of Bengal to mimic paths followed by litter once it reaches the sea. The farthest distance traveled by any of the bottles was 2,845 kilometers, which took 94 days.

This study demonstrates that future research could use bottle tags to significantly boost understanding of plastic litter’s movement through rivers and into oceans. These devices could reveal new insights into areas where plastic litter is likely to accumulate and periods when large amounts of plastic pollution are moving through the waterways.

The authors also highlight the potential for bottle tags to engage the public — such as by enabling people to follow the bottles’ journeys for themselves — potentially boosting awareness, discouraging littering, and informing changes to pollution policy.

The authors add: “Our ‘message in a bottle’ tags show how far and how fast plastic pollution can move. It demonstrates that this is a truly global issue, as a piece of plastic dropped in a river or ocean could soon wash up on the other side of the world.”make a difference: sponsored opportunity


Story Source:

Materials provided by PLOSNote: Content may be edited for style and length.


Journal Reference:

  1. Emily M. Duncan, Alasdair Davies, Amy Brooks, Gawsia Wahidunnessa Chowdhury, Brendan J. Godley, Jenna Jambeck, Taylor Maddalene, Imogen Napper, Sarah E. Nelms, Craig Rackstraw, Heather Koldewey. Message in a bottle: Open source technology to track the movement of plastic pollutionPLOS ONE, 2020; 15 (12): e0242459 DOI: 10.1371/journal.pone.0242459

FOR MORE INFORMATION: PLOS. “Satellite-tagged bottles show promise for tracking plastic litter through rivers: Researchers successfully track ‘bottle tags’ through Ganges River system into Bay of Bengal.” ScienceDaily. ScienceDaily, 2 December 2020. <www.sciencedaily.com/releases/2020/12/201202192806.htm>.

Climate change warms groundwater in Bavaria

Climate change warms groundwater in Bavaria - Naveen Bharat eन्यूज़ पोर्टल  - Today's Truth

Groundwater reservoirs in Bavaria have warmed considerably over the past few decades. A new study by researchers at Martin Luther University Halle-Wittenberg (MLU) compares temperatures at 35 measuring stations, taken at different depths, with data from the 1990s. Water found at a depth of 20 metres was almost one degree warmer on average than 30 years ago. The findings were published in the journal “Frontiers in Earth Science.”

As the air warms, the ground also becomes warmer over time — ultimately resulting in warmer groundwater. Geologists call this thermal coupling. “Unlike the atmosphere, however, the earth’s sub-surface is very sluggish,” explains Professor Peter Bayer, a geoscientist at MLU and co-author of the study. Because the ground below the surface does not react to short-term temperature fluctuations and thus tends to reflect long-term trends, it is a good indicator of climate change.

“This ground warming effect has been known to scientists, however there is still little data on it,” explains Bayer. For the new study, Bayer and his doctoral student Hannes Hemmerle repeated measurements that had been carried out in the 1990s at 35 measuring stations in groundwater reservoirs in Bavaria. The measuring points are distributed throughout the state, which provides a rare insight into the development of an entire region.

The geologists were able to show that almost all the groundwater reservoirs they investigated had warmed up in a similar way over the decades. “Climate change has a very clear effect at depths starting at around 15 metres; at that point short-term local or seasonal fluctuations can no longer be measured,” explains Hemmerle. The groundwater at depths of 20 metres was, on average, nearly 0.9 degrees Celsius warmer than in the 1990s. At depths of 60 metres it was still nearly 0.3 degrees warmer. During the same period, the average air temperature rose by 1.05 degrees Celsius.

“It can be assumed that the groundwater will warm up even more as a delayed reaction to air temperatures and that it will continue to react to rising atmospheric temperatures in the future,” says Hemmerle. The consequences of this warming are still difficult to gauge, says Bayer, who adds, higher water temperatures affect the growth of microbes and put pressure on underground ecosystems that are adapted to very constant temperatures.

In order to get a feel for the magnitude of the measurements, Bayer and Hemmerle also compared ground warming at a depth of 15 metres with Bavaria’s annual heating requirements. Their findings: the increase in temperature correlates to about ten percent of demand. “At least a portion of the heat could possibly be reused as geothermal energy,” says Bayer. However, the results cannot be directly transferred to the whole of Germany. “But it can be assumed that the trend is the same,” says Hemmerle.make a difference: sponsored opportunity


Story Source:

Materials provided by Martin-Luther-Universität Halle-WittenbergNote: Content may be edited for style and length.


Journal Reference:

  1. Hannes Hemmerle, Peter Bayer. Climate Change Yields Groundwater Warming in Bavaria, GermanyFrontiers in Earth Science, 2020; 8 DOI: 10.3389/feart.2020.575894

FOR MORE INFORMATION: Martin-Luther-Universität Halle-Wittenberg. “Climate change warms groundwater in Bavaria.” ScienceDaily. ScienceDaily, 1 December 2020. <www.sciencedaily.com/releases/2020/12/201201124124.htm>.