Impact of wastewater systems on Edwards Aquifer evaluated

Environmental Monitor | Managing and Studying Texas's Edwards Aquifer

Southwest Research Institute developed an integrated hydrologic computer model to evaluate the impact of different types of wastewater disposal facilities on the Edwards Aquifer, the primary water source for San Antonio and its surrounding communities. The research results will guide authorities on what actions to take to protect the quality and quantity of water entering the aquifer.

The two-year study, which concluded in July, was funded through the City of San Antonio’s Edwards Aquifer Protection Plan (EAPP) under the direction of the San Antonio River Authority. The tax-funded EAPP identifies and protects land and water crucial to the well-being of the aquifer. SwRI researchers selected the nearly 25-square-mile Helotes Creek Watershed in northwest Bexar County as the study area. They combined surface and groundwater data, including streamflow and groundwater elevations, along with climate, soil and topographic input to create an integrated model of the watershed.

“We chose the Helotes Creek Watershed because it is entirely in the contributing and recharge zones of the Edwards Aquifer. Rainfall and bodies of water over these key zones replenish the aquifer,” said SwRI’s Mauricio Flores, who helped lead the project. “Our findings are intended to provide insight on which wastewater practices offer the best protection for the aquifer when considering new development in these critical zones.”

SwRI’s Water Resources group constructed a base case model, replicating what is happening now with septic systems already located in the watershed area. Starting with that data, they evaluated what would happen if they added wastewater disposal facilities to the region. Scenarios evaluated included additional septic or onsite sewage systems, facilities that reuse wastewater for irrigation and systems that dispose of wastewater in nearby creeks or rivers.

“We considered a range of hypothetical scenarios. The size and capacity of the hypothesized wastewater facilities were consistent with possible residential development in the Helotes Creek Watershed area,” said Dr. Ronald Green, SwRI technical advisor and project manager. “Our results predicted that installing additional wastewater systems in the region, regardless of type, would increase the amount of wastewater discharged to the environment and significantly degrade the watershed and the quality of water recharging the Edwards Aquifer.”

The Helotes Creek Watershed study was the first of its kind in this area. The findings are applicable to most watersheds in the aquifer’s contributing and recharge zones. However, SwRI researchers recommend expanding the study to outside of Bexar County to demonstrate how development and increased wastewater disposal would impact these areas.

“The results of the study not only highlight the impact development could have on the aquifer, but can also be used to prioritize protection of land, rivers and streams that recharge the aquifer,” said Flores. “Our findings show this type of research is vital to protecting important water resources.”

The City of San Antonio is conducting additional EAPP-funded research aimed at protecting the aquifer. An official city report, which will include the SwRI study, is expected in 2023.make a difference: sponsored opportunity

Story Source:

Materials provided by Southwest Research InstituteNote: Content may be edited for style and length.

FOR MORE INFORMATION: Southwest Research Institute. “Impact of wastewater systems on Edwards Aquifer evaluated.” ScienceDaily. ScienceDaily, 20 October 2020. <>.

Understanding how toxic PFAS chemicals spread from release sites

Cancer-causing chemical in drinking water traced to fire-fighting foam |  Berkeley News

A study led by Brown University researchers sheds new light on how pollutants found in firefighting foams are distributed in water and surface soil at release sites. The findings could help researchers to better predict how pollutants in these foams spread from the spill or release sites — fire training areas or airplane crash sites, for example — into drinking water supplies.

Firefighting foams, also known as aqueous film forming foams (AFFF), are often used to combat fires involving highly flammable liquids like jet fuel. The foams contain a wide range of per- and polyfluoroalkyl substances (PFAS) including PFOA, PFOS and FOSA. Many of these compounds have been linked to cancer, developmental problems and other conditions in adults and children. PFAS are sometimes referred to as “forever chemicals” because they are difficult to break down in the environment and can lead to long-term contamination of soil and water supplies.

“We’re interested in what’s referred to as the fate and transport of these chemicals,” said Kurt Pennell, a professor in Brown’s School of Engineering and co-author of the research. “When these foams get into the soil, we want to be able to predict how long it’s going to take to reach a water body or a drinking water well, and how long the water will need to be treated to remove the contaminants.”

It had been shown previously that PFAS compounds tend to accumulate at interfaces between water and other substances. Near the surface, for example, PFAS tend to collect at the air-water interface — the moist but unsaturated soil at the top of an aquifer. However, prior experiments showing this interface activity were conducted only with individual PFAS compounds, not with complex mixtures of compounds like firefighting foams.

“You can’t assume that PFOS or PFOA alone are going to act the same way as a mixture with other compounds,” said Pennell, who is also a fellow at the Institute at Brown for Environment and Society. “So this was an effort to try to tease out the differences between the individual compounds, and to see how they behave in these more complex mixtures like firefighting foams.”

Using a series of laboratory experiments described in the journal Environmental Science and Technology, Pennell and his colleagues showed that the firefighting foam mixture does indeed behave much differently than individual compounds. The research showed that the foams had a far greater affinity for the air-water interface than individual compounds. The foams had more than twice the interface activity of PFOS alone, for example.

Pennell says that insights like these can help researchers to model how PFAS compounds migrate from contaminated sites.

“We want to come up with the basic equations that describe the behavior of these compounds in the lab, then incorporate those equations into models that can be applied in field,” Pennell said. “This work is the beginning of that process, and we’ll scale it up from here.”

Ultimately, the hope is that a better understanding of the fate and transport of these compounds could help to identify wells and waterways at risk for contamination, and aid in cleaning those sites up.make a difference: sponsored opportunity

Story Source:

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

Journal Reference:

  1. jed costanza, Linda M. Abriola, Kurt D Pennell. Aqueous film-forming foams exhibit greater interfacial activity than PFOA, PFOS, or FOSAEnvironmental Science & Technology, 2020; DOI: 10.1021/acs.est.0c03117

FOR MORE INFORMATION: Brown University. “Understanding how toxic PFAS chemicals spread from release sites.” ScienceDaily. ScienceDaily, 15 October 2020. <>.

Solar-powered system extracts drinkable water from ‘dry’ air

What is solar energy?

Researchers at MIT and elsewhere have significantly boosted the output from a system that can extract drinkable water directly from the air even in dry regions, using heat from the sun or another source.

The system, which builds on a design initially developed three years ago at MIT by members of the same team, brings the process closer to something that could become a practical water source for remote regions with limited access to water and electricity. The findings are described today in the journal Joule, in a paper by Professor Evelyn Wang, who is head of MIT’s Department of Mechanical Engineering; graduate student Alina LaPotin; and six others at MIT and in Korea and Utah.

The earlier device demonstrated by Wang and her co-workers provided a proof of concept for the system, which harnesses a temperature difference within the device to allow an adsorbent material — which collects liquid on its surface — to draw in moisture from the air at night and release it the next day. When the material is heated by sunlight, the difference in temperature between the heated top and the shaded underside makes the water release back out of the adsorbent material. The water then gets condensed on a collection plate.

But that device required the use of specialized materials called metal organic frameworks, or MOFs, which are expensive and limited in supply, and the system’s water output was not sufficient for a practical system. Now, by incorporating a second stage of desorption and condensation, and by using a readily available adsorbent material, the device’s output has been significantly increased, and its scalability as a potentially widespread product is greatly improved, the researchers say.

Wang says the team felt that “It’s great to have a small prototype, but how can we get it into a more scalable form?” The new advances in design and materials have now led to progress in that direction.

Instead of the MOFs, the new design uses an adsorbent material called a zeolite, which in this case is composed of a microporous iron aluminophosphate. The material is widely available, stable, and has the right adsorbent properties to provide an efficient water production system based just on typical day-night temperature fluctuations and heating with sunlight.

The two-stage design developed by LaPotin makes clever use of the heat that is generated whenever water changes phase. The sun’s heat is collected by a solar absorber plate at the top of the box-like system and warms the zeolite, releasing the moisture the material has captured overnight. That vapor condenses on a collector plate — a process that releases heat as well. The collector plate is a copper sheet directly above and in contact with the second zeolite layer, where the heat of condensation is used to release the vapor from that subsequent layer. Droplets of water collected from each of the two layers can be funneled together into a collecting tank.

In the process, the overall productivity of the system, in terms of its potential liters per day per square meter of solar collecting area (LMD), is approximately doubled compared to the earlier version, though exact rates depend on local temperature variations, solar flux, and humidity levels. In the initial prototype of the new system, tested on a rooftop at MIT before the pandemic restrictions, the device produced water at a rate “orders of magnitude” greater that the earlier version, Wang says.

While similar two-stage systems have been used for other applications such as desalination, Wang says, “I think no one has really pursued this avenue” of using such a system for atmospheric water harvesting (AWH), as such technologies are known.

Existing AWH approaches include fog harvesting and dew harvesting, but both have significant limitations. Fog harvesting only works with 100 percent relative humidity, and is currently used only in a few coastal deserts, while dew harvesting requires energy-intensive refrigeration to provide cold surfaces for moisture to condense on — and still requires humidity of at least 50 percent, depending on the ambient temperature.

By contrast, the new system can work at humidity levels as low as 20 percent and requires no energy input other than sunlight or any other available source of low-grade heat.

LaPotin says that the key is this two-stage architecture; now that its effectiveness has been shown, people can search for even better adsorbent materials that could further drive up the production rates. The present production rate of about 0.8 liters of water per square meter per day may be adequate for some applications, but if this rate can be improved with some further fine-tuning and materials choices, this could become practical on a large scale, she says. Already, materials are in development that have an adsorption about five times greater than this particular zeolite and could lead to a corresponding increase in water output, according to Wang.

The team continues work on refining the materials and design of the device and adapting it to specific applications, such as a portable version for military field operations. The two-stage system could also be adapted to other kinds of water harvesting approaches that use multiple thermal cycles per day, fed by a different heat source rather than sunlight, and thus could produce higher daily outputs.make a difference: sponsored opportunity

Story Source:

Materials provided by Massachusetts Institute of Technology. Original written by David L. Chandler. Note: Content may be edited for style and length.

Journal Reference:

  1. Alina LaPotin, Yang Zhong, Lenan Zhang, Lin Zhao, Arny Leroy, Hyunho Kim, Sameer R. Rao, Evelyn N. Wang. Dual-Stage Atmospheric Water Harvesting Device for Scalable Solar-Driven Water ProductionJoule, 2020; DOI: 10.1016/j.joule.2020.09.008

FOR MORE INFORMATION: Massachusetts Institute of Technology. “Solar-powered system extracts drinkable water from ‘dry’ air: Engineers have made their initial design more practical, efficient, and scalable.” ScienceDaily. ScienceDaily, 14 October 2020. <>.

Hurricanes, heavy rains are critical for Hawai’i’s groundwater supply

Hawaiian Islands - Wikipedia

Located within the most isolated archipelago in the world, Hawai’i is critically dependent on a clean, ample supply of fresh water. New research led by University of Hawai’i at M?noa scientists indicates that rain brought to the islands by hurricanes and Kona storms can often be the most important precipitation for re-supplying groundwater in many regions of the island of O’ahu.

“The majority of Hawai’i’s freshwater comes from groundwater,” said Daniel Dores, lead author and groundwater and geothermal researcher in the UH M?noa School of Ocean and Earth Science and Technology. “In this study, we investigated the relationship between trade wind showers, major rainfall events like Kona storms, and groundwater.”

Dores and a team of scientists from SOEST and the Hawai’i Department of Health collected rainfall around the island of Oahu and analyzed the stable isotopes of rainwater, chemical signatures in the water molecules. They compared the chemical signatures in rainwater to those of groundwater to determine the source of water in the aquifers — event-based rainfall or trade wind-related rain.

“Because windward and mauka showers are so common, it is easy to assume that is the main source of our drinking water,” said Dores. “Also, large rainfall events such as Kona storms result in significant runoff into the oceans. However, our research found that a lot of the rain from Kona storms makes it into our groundwater aquifers and is an important source of our drinking water.”

Hawai’i is experiencing substantial changes in trade wind weather patterns, and precipitation events could become more extreme. Some of the study co-authors will continue research to understand more about local and regional groundwater recharge and water quality.

“By better understanding how our groundwater is impacted by these extreme precipitation events, we can better protect the resource itself,” said Dores.make a difference: sponsored opportunity

Story Source:

Materials provided by University of Hawaii at Manoa. Original written by Marcie Grabowski. Note: Content may be edited for style and length.

Journal Reference:

  1. Daniel Dores, Craig R. Glenn, Giuseppe Torri, Robert B. Whittier, Brian N. Popp. Implications for groundwater recharge from stable isotopic composition of precipitation in Hawai’i during the 2017–2018 La NiñaHydrological Processes, 2020; DOI: 10.1002/hyp.13907

FOR MORE INFORMATION: University of Hawaii at Manoa. “Hurricanes, heavy rains are critical for Hawai’i’s groundwater supply.” ScienceDaily. ScienceDaily, 13 October 2020. <>.

How urban grime affects chemical reactions in cities

Urban grime causes air pollution, finds study | ArchitectureAU

Many city surfaces are coated with a layer of soot, pollutants, metals, organic compounds and other molecules known as “urban grime.” Chemical reactions that occur in this complex milieu can affect air and water quality. Now, researchers reporting in ACS Earth and Space Chemistry have taken a closer look at urban grime collected from two U.S. cities, revealing for the first time that the material absorbs sunlight and therefore might participate in photochemical reactions.

Scientists have previously analyzed lab-prepared urban grime, as well as samples collected from cities, but they still don’t have a complete understanding of what’s in the material, or how it varies by location. Some components can react with other molecules in the grime or air, which could affect what gets released into the atmosphere or into the water when it rains. To better understand these processes, Tara Kahan and colleagues wanted to investigate the physical properties, light absorption and composition of urban grime samples collected from Syracuse, New York, and Scranton, Pennsylvania.

The researchers collected samples of urban grime from Syracuse by placing vertical quartz plates outdoors for 30 days and then analyzed the surfaces. Although urban grime was long thought to be predominantly a film, the samples showed collections of particles, rather than a uniform film, consistent with evidence from other recent studies. In different experiments, the team scraped grime from wet exterior surfaces of windows in both cities and analyzed their compositions. The results were similar to those reported from other cities in Canada and Europe, but there were differences in specific ions. For example, higher chloride levels were found in North American cities, which could be from the use of road salt in the winter, whereas higher sulfate levels were reported in some European cities, likely because of coal combustion. The team also observed that urban grime absorbed light at wavelengths found in sunlight, which suggests that the sun could speed up or slow down chemical reactions that affect air and water quality in cities.make a difference: sponsored opportunity

Story Source:

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

Journal Reference:

  1. Corey R. Kroptavich, Shan Zhou, Shawn F. Kowal, Tara F. Kahan. Physical and Chemical Characterization of Urban Grime Sampled from Two CitiesACS Earth and Space Chemistry, 2020; DOI: 10.1021/acsearthspacechem.0c00192

FOR MORE INFORMATION: American Chemical Society. “How urban grime affects chemical reactions in cities.” ScienceDaily. ScienceDaily, 30 September 2020. <>.

New climate model helps researchers better predict water needs

How much water should you drink? - Harvard Health

New research from the FAMU-FSU College of Engineering combines climate and land use projections to predict water availability, information that is crucial for the preparations of resource managers and land-use planners.

“This research presented a new method that can be used to generate future climate data for the existing hydrological models,” said Gang Chen, a professor of civil and environmental engineering at the college. “With the integration of more reliable future climate data, the existing hydrological models can more accurately project future water scenarios in the face of climate change.”

Chen is leading a team of experts to produce new data techniques to improve hydrological modeling that is essential for water resource management planning. Their work was published in WATER.

The researchers used their method to examine the hydrological processes in Alabama’s Upper Choctawhatchee River Watershed, which eventually flows into Florida and empties into the Choctawhatchee Bay. They integrated land use projections with future climate data to study the combined effects on the hydrological response of the watershed.

“Using water balance simulations, we discovered that surface runoff and evapotranspiration are dominant pathways for water loss in the Southeast,” Chen said.

Yashar Makhtoumi, a doctoral candidate in the Department of Civil and Environmental Engineering, is working with Chen on new data downscaling techniques. The innovative process provides more data and improves modeling outcomes.

“Few research projects have been done to investigate the combined effects of land use change and climate change using projections,” Makhtoumi said.

The results of the study showed the effects on water resource variables were seasonal. Surface runoff caused the most significant changes in various simulations, and evapotranspiration was also an issue, though to a lesser degree. The models indicate that by midcentury, more frequent extremes in water balance are projected to be an issue.

Although the research focuses on a single watershed, the researchers believe their work could be applicable on a wider scale. That’s important for a state like Florida, where population growth, development and climate change are forcing residents and planners to realize the limitations of the state’s water supply.

“Our model demonstrated that it could capture hydrologic parameters accurately and could be used for future studies of water quality,” Chen said. “It can provide the necessary data to determine sustainable conservation practices needed now and in the future, and help manage and protect our water resources.”

Researchers from Florida A&M University and California State Polytechnic University Pomona contributed to this work.

The research was supported by a $1.2 million grant from the National Institute of Food and Agriculture of the U.S. Department of Agriculture through Florida A&M University.make a difference: sponsored opportunity

Story Source:

Materials provided by Florida State University. Original written by Trisha Radulovich. Note: Content may be edited for style and length.

Journal Reference:

  1. Yashar Makhtoumi, Simeng Li, Victor Ibeanusi, Gang Chen. Evaluating Water Balance Variables under Land Use and Climate Projections in the Upper Choctawhatchee River Watershed, in Southeast USWater, 2020; 12 (8): 2205 DOI: 10.3390/w12082205

FOR MORE INFORMATION: Florida State University. “New climate model helps researchers better predict water needs.” ScienceDaily. ScienceDaily, 6 October 2020. <>.

The Colorado river’s water supply is predictable owing to long-term ocean memory

Colorado River - Pacific Institute

A team of scientists at Utah State University has developed a new tool to forecast drought and water flow in the Colorado River several years in advance. Although the river’s headwaters are in landlocked Wyoming and Colorado, water levels are linked to sea surface temperatures in parts of the Pacific and Atlantic oceans and the water’s long-term ocean memory. The group’s paper, “Colorado River water supply is predictable on multi-year timescales owning to long-term ocean memory” was published October 9 by Communications Earth and Environment, an open-access journal from Nature Research.

The Colorado River is the most important water resource in the semi-arid western United States and faces growing demand from users in California, Arizona, New Mexico, Colorado and Utah. Because water shortages in the Colorado River impact energy production, food and drinking water security, forestry and tourism, tools to predict drought and low water levels could inform management decisions that affect millions of people.

Current drought forecasts focus on short-term indicators which limits their usefulness because short-term weather phenomena have too great an influence on the models.

“This new approach is robust and means that water managers, for the first time, have a tool to better estimate water supply in the Colorado River for the future,” Robert Gillies, professor in USU’s Department of Plants, Soils and Climate (PSC) and director of the Utah Climate Center, said. “The model can be run iteratively so every year a new forecast for the next three years can be created.”

In addition to ocean memory, water flows are impacted by land systems — including soils, groundwater, vegetation, and perennial snowpack — which play important roles in tempering the effects of short-term precipitation events. The researchers hypothesized that multi-year predictions could be achieved by using long-term ocean memory and associated atmospheric effects and the filtering effects of land systems.

The study’s lead author, Yoshimitsu Chikamoto, assistant professor of earth systems modeling in USU’s PSC department, said the components of the complex climate model include simulations of clouds and aerosols in the atmosphere, land surface characteristics, ocean currents and mixing and sea surface heat and water exchange.

“These predictions can provide a more long-term perspective,” Chikamoto said. “So if we know we have a water shortage prediction we need to work with policymakers on allocating those water resources.”

Simon Wang, USU professor of climate dynamics, said water managers and forecasters are familiar with El Niño and La Niña and the ocean’s connections to weather in the southwestern U.S. However, the upper basin of the Colorado River is not in the southwest and forecasts have not connected the dynamics of parts of the oceans with the Colorado River as the new forecasting tool does.

Matt Yost, PSC assistant professor and USU Extension agroclimate specialist, said having a two-year lead-time on preparing for drought could have a huge impact on farmers as they plan crop rotations and make other business decisions.

Co-author Larissa Yocom, assistant professor of fire ecology in USU’s Department of Wildland Resources, said a tool that can provide a long-term forecast of drought in areas impacted by the Colorado River could give managers a jump-start in preparing for wildland fire seasons.

Wang said Utah Climate Center researchers have developed models of drought cycles in the region and have recently studied the dynamics of river flows and shrinking water levels in the Great Salt Lake.

“In doing that work, we know that water managers don’t have tools to forecast Colorado River flows very long into the future and that is a constraint on what they can do,” Wang said. “We have built statistical models in the past, and Yoshi (Chikamoto) has expertise and in-depth knowledge of ocean dynamics so we talked about giving this idea a try because we found nothing in the literature to model these dynamics in the upper basin.”

“Using our tool we can develop an operational forecast of the Colorado River’s water supply,” Chikamoto added

Story Source:

Materials provided by Utah State University. Original written by Lynnette Harris. Note: Content may be edited for style and length.

Journal Reference:

  1. Yoshimitsu Chikamoto, S.-Y. Simon Wang, Matt Yost, Larissa Yocom, Robert R. Gillies. Colorado River water supply is predictable on multi-year timescales owing to long-term ocean memoryCommunications Earth & Environment, 2020; 1 (1) DOI: 10.1038/s43247-020-00027-0

FOR MORE INFORMATION: Utah State University. “The Colorado river’s water supply is predictable owing to long-term ocean memory: Scientists develop new tool to forecast drought and water flow in the Colorado river.” ScienceDaily. ScienceDaily, 9 October 2020. <>.

HotSpots H2O: Wildfire Threaten Cheyenne Water Supply

The sky over Medicine Bow-Routt National Forests as the Mullen Fire just begins. Photo © ClarkHarrisinWY

The Mullen Fire, which has spread through more than 147,000 acres of Colorado and Wyoming forest in the past two weeks, reached the southern edge of the main drinking water source for Cheyenne, the Wyoming capital. Protection of Rob Roy Reservoir is a major priority, city officials say.

The wildfire began September 17, feeding on soaring winds and burning through dead timber, bush, and beetle-killed pine in the Medicine Bow-Routt National Forests. Firefighters have worked to slow its progress, yet the fire doubled in size last week. Mandatory evacuation orders are in effect for some Colorado and Wyoming residents.

Rob Roy Reservoir, the first step in Cheyenne’s drinking water system, is at the edge of the burn zone. The city pipes water from the reservoir to Lake Owen, a secondary storage site. After Lake Owen, water makes its way through two more reservoirs before entering the city treatment facility.

Although the facility can treat water polluted by fires, authorities are concerned about erosion at the reservoir, which could damage pipelines and degrade water quality. If sediment or debris is washed into the reservoir, it could trigger problems with the treatment process.

Clint Bassett, the Board of Public Utilities treatment manager, said Cheyenne officials are working closely with the U.S. Forest Service to protect the watersheds, which are west of the city.

“We don’t know the impact of the Mullen Fire at this time, but the location suggests there may be some adverse effects to the city of Cheyenne’s water collection system and water quality,” Bassett said in a news release.

Yellow sky from the Mullen Fire in The Buttes, Wyoming. © CW George

Rob Roy Reservoir isn’t the only water-supply asset under threat during the recent wildfires in the western United States. More than 5 million acres of land has burned this year just in California, Oregon, and Washington, destroying water infrastructure and damaging watersheds.

In California’s Santa Cruz County, the San Lorenzo Valley Water District discovered that more than 7 miles of plastic water pipeline melted in the CZU Lightning Complex Fire in late August. The next month in Oregon, the water treatment plant for the town of Detroit was destroyed in the Lionshead Fire.

Burned land and vegetation leave scars that last for years. They prevent water from fully absorbing into the earth, weaken the watershed, and cause more intense flooding and mudslides. Even a light rainstorm can unleash sediment after a severe wildfire.

Vegetation takes time to grow back. Jason Kean, a research hydrologist at the U.S. Geological Survey’s Landslide Hazard Program, told E&E News that depending on the size and intensity of the fire, it can take two to five years, if not longer, for the watershed to heal.

Fires can also poison drinking water with benzene and other harmful volatile organic chemicals. These contaminants could be released when plastic pipes melt. They could also be sucked into pipes when a water system loses pressure. Some residents of San Lorenzo Valley Water District have been told to not drink the water because of benzene contamination.

A study released earlier this year examined two destructive fires in California: the 2017 Tubbs Fire and the 2018 Camp Fire. The study found that not only do melted plastics and debris contaminate water, but polluted water can then contaminate piping and water supplies by flowing through any undamaged infrastructure.

The federal limit for benzene in drinking water is 5 parts per billion. Some drinking water samples from the Camp Fire came back with more than 2,000 parts per billion. From the Tubbs Fire, more than 40,000.


Redefining drought in the US corn belt

Drought and Your Health

As the climate trends warmer and drier, global food security increasingly hinges on crops’ ability to withstand drought. But are scientists and producers focusing on the right metric when measuring crop-relevant drought? Not exactly, according to new research from University of Illinois scientists, who urge the scientific community to redefine the term.

“Plants have to balance water supply and demand. Both are extremely critical, but people overlook the demand side of the equation, especially in the U.S. Corn Belt,” says Kaiyu Guan, principal investigator on two new studies, Blue Waters professor in the Department of Natural Resources and Environmental Sciences and the National Center for Supercomputing Applications at Illinois.

The demand Guan refers to is atmospheric dryness, often expressed as vapor pressure deficit (VPD). The drier the air, the more moisture is sucked out of pores, or stomata, in plant leaves. Plants have to open stomata to take in carbon dioxide as their food, but if they sense the atmosphere is too dry, they’ll close pores to avoid drying out. Keeping stomata closed too long leads to reductions in photosynthesis, plant growth, and grain yield.

The kicker? Plants shut down stomata due to atmospheric dryness even when there’s an adequate supply of moisture in the soil.

“If you only consider rainfall and soil moisture, which is how most people think about drought, that’s mostly describing the supply side. Of course if you have low soil moisture, plants will be stressed by how much water they get. But the supply is often pretty sufficient, especially here in the U.S. Corn Belt,” Guan says. “However, the demand side from the atmosphere can also severely stress plants. We need to pay more attention to that drought signal.”

Guan’s two recent studies used multiple technological approaches, including field measurements, various sources of satellite data, hydrological model simulations, and government crop yield statistics. The first study, published in Agricultural and Forest Meteorology, used data from seven sites across the Corn Belt to conclude VPD accounts for nearly 90% of the changes in crop stomatal conductance, a proxy for drought stress, and approximately 85% of changes in gross primary productivity, a measure of productivity.

“By comparison, soil moisture typically accounts for 6-13% of these measures for corn and soybean, and up to 35% when considering time lag effects,” says Hyungsuk Kimm, doctoral student in Guan’s group and the study’s lead author.

In the other study, published in the Journal of Hydrology, Guan’s team focused on grain yield. Yield depends on many factors related to water cycles, but the researchers found that VPD explains the biggest proportion of variability in crop yield and also provides the earliest warning for yield loss when comparing with other water cycle metrics and traditional drought indices.

“This led us to build a new drought index integrating VPD, soil moisture, and measures of evapotranspiration, which can account for more than 70% of yield variation. Our index outperforms all the existing drought indices,” says Wang Zhou, postdoctoral researcher in Guan’s group and the study’s lead author.

Guan adds, “In these two studies, we tried to understand the demand side of drought from two major angles, one using eddy covariance data which measures landscape water and carbon use very accurately — the gold standard — and the other leveraging satellite data and model-simulated hydrological variables correlated with regional yield,” Guan says. “In both, we demonstrate VPD is more important than soil moisture to explain the crop drought response in the U.S. Midwest.”

Adjusting the drought concept for crops will be critical for global food security under a changing climate.

“When we look at climate change scenarios, the amount of rainfall is not changing much for the Corn Belt, but we for sure know temperature and VPD will increase here. That means not much will change on the supply side, but demand stress will increase significantly. And that type of stress is so connected to end-of-season crop yield,” Guan says.

His group is working on follow-up studies evaluating the role of irrigation in increasing supply and decreasing demand, but for now, Guan says breeding for improved water-use-efficiency could be an important part of the solution.make a difference: sponsored opportunity

Story Source:

Materials provided by University of Illinois College of Agricultural, Consumer and Environmental Sciences. Original written by Lauren Quinn. Note: Content may be edited for style and length.

Journal Reference:

  1. Wang Zhou, Kaiyu Guan, Bin Peng, Jiancheng Shi, Chongya Jiang, Brian Wardlow, Ming Pan, John S. Kimball, Trenton E. Franz, Pierre Gentine, Mingzhu He, Jingwen Zhang. Connections between the hydrological cycle and crop yield in the rainfed U.S. Corn BeltJournal of Hydrology, 2020; 590: 125398 DOI: 10.1016/j.jhydrol.2020.125398

FOR MORE INFORMATION: University of Illinois College of Agricultural, Consumer and Environmental Sciences. “Redefining drought in the US corn belt.” ScienceDaily. ScienceDaily, 30 September 2020. <>.

Federal Water Tap, October 5: Army Corps Evaluates Multibillion-Dollar Flood Projects for Houston

Federal Water Tap Archives - Circle of Blue

The Rundown

The Army Corps of Engineers wants public input as it assesses ways to reduce flood risk along Houston waterways. FEMA begins accepting applications for $500 million in flood resilience grants. The Department of Health and Human Services wants to test sewage as a coronavirus early-warning system. Three agencies sign a new management plan for federal dams in the Columbia River basin. Regulators say there is enough evidence to list two freshwater mussel species as threatened. USDA begins accepting applications for a pilot program for septic systems that fail due to unsuitable soil. And lastly, the EPA considers revising up to eight national drinking water rules.

By the Numbers

$500 million: Grant funding available to help communities reduce the risk of catastrophic floods. Of that amount, some $20 million is set aside for tribes. The Building Resilient Infrastructure and Communities grants encourage projects that update building codes and those that incorporate nature-based flood prevention: things like wetlands, green spaces, and room for water to flow. (FEMA)

$5 million: Grant funding available for a new pilot program to evaluate and test small-scale wastewater treatment systems for poor communities with septic systems that fail due to unsuitable soil. Applications from regional research collaboratives are due November 4 and can be submitted via (USDA)

In context: Septic Infrastructure in the U.S.

News Briefs

Tracking the Coronavirus in Sewage
The Department of Health and Human Services is seeking a contractor that could help test sewage for traces of the new coronavirus, CNBC reports.

Evidence of genetic material from the SARS-CoV-2 virus in sewage can be used to identify potential outbreaks more quickly than clinical data. The CDC has already said it would organize a national surveillance network.

The department says that testing will begin with a network of wastewater plants that treat the sewage of about 10 percent of U.S. residents. The project could scale up to cover about 30 percent of the country’s population, largely in the biggest cities.

CNBC notes that the solicitation appears to be tailored toward the services of a particular company: BioBot, a startup that began testing sewage earlier this year and now has partnerships in 42 states.

Threatened Mussels
The U.S. Fish and Wildlife Service says that there is enough evidence to list two freshwater mussel species as “threatened” under federal protection laws.

Critical habitat for the longsolid and round hickorynut mussels extends from Alabama to Pennsylvania. This includes about 1,000 miles of river habitat.

Comments on the proposed listing are being accepted through December 28. Submit them via using docket number FWS-R4-ES-2020-0010.

Studies and Reports

Houston Flooding Study
The Army Corps of Engineers released an interim report as part of its assessment of ways to reduce flooding risk along Houston’s Buffalo Bayou.

Options include a new reservoir (estimated cost: $2.1 billion to $2.9 billion), dredging and widening Buffalo Bayou ($946 million to $1.2 billion), and relocating businesses and apartments downstream ($2.3 billion). There are a number of smaller options that could be included in those three options.

The Corps operates two dams on the bayou and its tributaries, which were inundated during Hurricane Harvey in 2017. Several factors account for the area’s increasing flood risk since the dams were built in the 1940s: population growth, more pavement, and higher-intensity rainfall.

The interim report does not make any conclusions or recommendations. Those will be part of the final report. Before then, the public has a chance to weigh in. Submit comments by November 2 to

Columbia River Dams
Three federal agencies signed a record of decision on a new management plan for federal dams in the Columbia River basin.

Intended to improve the health of the basin’s salmon runs while accounting for the dams’ other authorized purposes — flood control, navigation, hydropower, water supply — the plan prioritizes spilling more water from the dams. Spilling water is a way to prevent outbound salmon from being killed in the turbines.

The plan does not take the step that some environmental groups and tribes had wanted: breaching four dams on the Lower Snake River.

On the Radar

EPA Drinking Water Rules Review
Every six years, the EPA is required to review federal drinking water rules to determine, based on new data, whether any require revision.

The latest review found eight rules that could need updating. Those rules relate to microbial contaminants like Legionella and Giardia, as well as the chemical byproducts of water disinfection.

The agency will hold an online meeting on October 14 and 15 to hear expert testimony and public input about potential revisions.

The agenda is here. Register via the above link by October 12.

In context: Who Regulates U.S. Drinking Water, and How?

Environmental Finance Board Meeting
Scheduling conflict alert: the Environmental Finance Advisory Board, which advises the EPA on the important question ‘How to pay for it?’, will hold a public meeting on October 14 and 15.

On the agenda: the EPA Office of Water will respond to a board report on stormwater financing and consolidating smaller water systems in regional blocs.

What Is a Showerhead
The Department of Energy is giving the public an additional two weeks to comment on its proposal to revise the definition of “showerhead.”

The revision would allow for high-end, multi-nozzle fixtures to use more water than current efficiency standards.

Submit comments by October 14. Send them to with the subject line EERE-2014-BT-TP-0002.