UN World Water Development Report 2021 ‘Valuing Water’

The United Nations World Water Development Report (WWDR) 2021, published by UNESCO on behalf of UN-Water, shows that the inability to recognize the value of water is the main cause of water waste and misuse. Despite the difficulty of attributing an objective and indisputable value to a resource which is fundamental to life, it seems necessary to examine water’s various dimensions in order to understand the various aspects of its “value”. This is especially true in times of growing scarcity and against the backdrop of population growth and climate change.

“Water is our most precious resource, a ‘blue gold’ to which more than 2 billion people do not have direct access. It is not only essential for survival, but also plays a sanitary, social and cultural role at the heart of human societies,” says the Director-General of UNESCO, Audrey Azoulay.

This year’s WWDR addresses the question of the value of water. It shows that waste and careless use stems from the fact we all too often think of water exclusively in terms of its cost price, without realizing its tremendous value, which is impossible to price.

“The devastating effects of the COVID-19 pandemic remind us of the importance of having access to water, sanitation and hygiene facilities, and highlight that far too many people are still without them. Many of our problems arise because we do not value water highly enough; all too often water is not valued at all,” says Gilbert F. Houngbo, Chair of UN-Water and President of the International Fund for Agricultural Development (IFAD).

The value of water is certainly incalculable and limitless, since life cannot exist without it and it has no replacement. This is perhaps best illustrated by the widespread enthusiasm for the idea that traces of water can be found on Mars, or the fact that we think of water and life as interchangeable when studying other planets.

The report emphasizes the great need to broaden the notion of the “value” of water stressing that we cannot confuse the concepts of “price”, “cost” and “value”.

Although price and cost are potentially quantifiable, the concept of “value” is much wider and includes social and cultural dimensions.

Indeed, water is not like other raw materials which can be treated as commodities and openly traded through stock markets. The challenge is to determine a value for a resource whose importance varies in different areas of economic activity, at different times, without forgetting to take into account its social, environmental and cultural dimensions.

Tools and methodologies for valuing water are both imperfect and misapplied

The tools we have today tend to reduce the value of water to its economic aspect.

The economic value of water cannot be denied considering its myriad uses in food, electricity and industrial production, to name just a few.

While monetary valuation has the advantage of convenience and easy legibility in agriculture and industry, it presents the disadvantage of underestimating, even excluding, other aspects which are more difficult to monetize. How do we quantify the meaning of the 443 million schooldays missed annually due to water-related diseases?

Furthermore, some societies reject the idea of viewing nature and its benefits from an economic perspective, putting the rights of “Mother Earth” to the fore, thus rendering such economic readings of the value of water woefully inadequate.

In India, for example, the Ganges is revered by Hindus as a living entity with the same rights as human beings. Similarly, in New Zealand, the Te Awa Tupua Act of 2017 recognizes the Whanganui River as “an indivisible and living whole from the mountains to the sea” and guarantees the river’s protection by the local Maori population. “The fate of humans and water is inextricably linked. In the words of the Whanganui River Tribe’s proverb, Ko au te awa, ko te awa ko au, I am the river, the river is me”, notes Audrey Azoulay.

Faced with these views and those of investors, who consider that resources such as water can have an economic value put on them, it becomes difficult to develop a standard system to measure the value of water in all its aspects. Nevertheless, it is possible to develop an integrated approach that allows the different dimensions of water to be considered together, so as to identify appropriate policy choices. A key element of such an approach is to ensure that all stakeholders, regardless of background or gender, are involved in evaluations and decision-making. If we want to enrich our approach to water and stop reducing the resource to its mere monetary value, we must be enriched by the views held by all, especially the people directly concerned.

Overcoming differences of opinion and reaching the necessary compromises is one of the great challenges of water management. “The time has come for stakeholders to identify, articulate and share perspectives of the values of water,” emphasizes UN-Water Chair, Gilbert F. Houngbo. This implies developing mechanisms that allow stakeholders not only to express themselves but also to be heard.

When major infrastructure projects are studied, for example, it is essential to consider all these different dimensions, to ensure that their social, cultural and environmental consequences are not underestimated. A cost-benefit approach therefore requires considering the different “values” of water.

Similarly, we know that providing universal access to safe drinking water and sanitation in 140 low- and middle-income countries would cost $114 billion per year, whereas the multiple social and economic benefits of safe water are difficult to evaluate.

These issues are at the heart of this year’s edition of the United Nations World Water Development Report (WWDR), UN-Water’s flagship publication on water and sanitation issues, which focuses on a different theme every year.

The report is published by UNESCO on behalf of UN-Water and its production is coordinate by the UNESCO World Water Assessment Programme. The report gives insight into the main trends concerning the state, use and management of freshwater and sanitation, based on work by members and partners of UN-Water.

Launched in conjunction with World Water Day, the report provides decision-makers with knowledge and tools to formulate and implement sustainable water policies. It also offers best practice examples and in-depth analyses to stimulate ideas and actions for better stewardship in the water sector and beyond.

FOR MORE INFORMATION: United Nations Water

Increased winter snowmelt threatens western US water resources

Snow on mountains

More snow is melting during winter across the West, a concerning trend that could impact everything from ski conditions to fire danger and agriculture, according to a new University of Colorado Boulder analysis of 40 years of data.

Researchers found that since the late 1970s, winter’s boundary with spring has been slowly disappearing, with one-third of 1,065 snow measurement stations from the Mexican border to the Alaskan Arctic recording increasing winter snowmelt. While stations with significant melt increases have recorded them mostly in November and March, the researchers found that melt is increasing in all cold season months — from October to March.

Their new findings, published today in Nature Climate Change, have important implications for water resource planning and may indicate fewer pristine powder days and crustier snow for skiers.

“Particularly in cold mountain environments, snow accumulates over the winter — it grows and grows — and gets to a point where it reaches a maximum depth, before melt starts in the spring,” said Keith Musselman, lead author on the study and research associate ,at the Institute of Arctic and Alpine Research (INSTAAR) at the University of Colorado Boulder.

But the new research found that melt before April 1 has increased at almost half of more than 600 stations in western North America, by an average of 3.5% per decade.

“Historically, water managers use the date of April 1 to distinguish winter and spring, but this distinction is becoming increasingly blurred as melt increases during the winter,” said Noah Molotch, co-author on the study, associate professor of geography and fellow at INSTAAR.

Snow is the primary source of water and streamflow in western North America and provides water to 1 billion people globally. In the West, snowy mountains act like water towers, reserving water up high until it melts, making it available to lower elevations that need it during the summer, like a natural drip irrigation system.

“That slow trickle of meltwater that reliably occurs over the dry season is something that we have built our entire water infrastructure on in the West,” said Musselman. “We rely very heavily on that water that comes down our rivers and streams in the warm season of July and August.”

More winter snowmelt is effectively shifting the timing of water entering the system, turning that natural drip irrigation system on more frequently in the winter, shifting it away from the summer, he said.

This is a big concern for water resource management and drought prediction in the West, which depends heavily on late winter snowpack levels in March and April. This shift in water delivery timing could also affect wildfire seasons and agricultural irrigation needs.

Wetter soils in the winter also have ecological implications. One, the wet soils have no more capacity to soak up additional water during spring melt or rainstorms, which can increase flash flooding. Wetter winter soils also keep microbes awake and unfrozen during a time they might otherwise lay dormant. This affects the timing of nutrient availability, water quality and can increase carbon dioxide emissions.

An underutilized data source

Across the western U.S., hundreds of thin, fluid-filled metal pillows are carefully tucked away on the ground and out of sight from outdoor enthusiasts. These sensors are part of an extensive network of long-running manual and automated snow observation stations, which you may have even used data from when looking up how much snow is on your favorite snowshoeing or Nordic skiing trail.

This new study is the first to compile data from all 1,065 automated stations in western North America, providing valuable statistical insight into how mountain snow is changing.

And by using automated, continuously recording snowpack stations instead of manual, monthly observations, the new research shows that winter melt trends are very widespread — at three-times the number of stations with snowpack declines, according to Musselman.

Snowpack is typically measured by calculating how much water will be produced when it melts, known as snow-water equivalent (SWE), which is affected by how much snow falls from the sky in a given season. But because winter snowpack melt is influenced more by temperature than by precipitation, it is a better indicator of climate warming over time.

“These automated stations can be really helpful to understand potential climate change impacts on our resources,” said Musselman. “Their observations are consistent with what our climate models are suggesting will continue to happen.”

Other authors on this publication include Nans Addor at the University of Exeter and Julie Vano at the Aspen Global Change Institute.

FOR MORE INFORMATION:  University of Colorado at Boulder

Federal Agencies Plan to Investigate Links between PFAS Exposure and Viral Illness

Two federal health agencies are planning to investigate potential links between exposure to toxic PFAS chemicals and susceptibility to viral illnesses like Covid-19.

The study would build on federally funded investigations of PFAS exposure in nine communities near U.S. military bases where the chemicals were found in drinking water. Researchers hope to enroll 4,075 people from those previous investigations in the new assessment.

A collaboration between the National Center for Environmental Health and the Agency for Toxic Substances and Disease Registry, the study will be based on health questionnaires sent to people who have already had blood samples drawn for the PFAS exposure assessments.

Laurel Schaider, a senior scientist at Silent Spring Institute, told Circle of Blue that the agencies can leverage their data on PFAS levels in blood serum to provide valuable insights on the connection between chemical exposure and disease.

“It provides a good opportunity to address some of these questions,” said Schaider, who is leading a separate ATSDR-funded study in two Massachusetts communities of the health impacts of PFAS exposure in drinking water.

The new federal assessment on PFAS and viral illness will support an emerging field of scientific inquiry. A decade ago, a study of more than 69,000 people in the Ohio River Valley found probable links between PFOA and chronic diseases like high cholesterol, thyroid disease, testicular cancer, and kidney cancer.

PFOA is one of the thousands of chemicals classified as PFAS. The compounds have been used in firefighting foam, nonstick cookware, waterproof jackets, and other commercial and industrial products. Called “forever chemicals” because they do not easily break down in the environment, the chemicals have been found in drinking water sources nationwide.

For PFAS exposures and viral illnesses, Schaider pointed to a growing body of evidence of the debilitating effects the chemicals have on the human immune system.

A 2016 National Toxicology Program review concluded that two of the chemicals, PFOS and PFOA, are hazardous to the immune system, weakening the body’s ability to fight pathogens.

Very few studies have investigated links with Covid-19. Philippe Grandjean of Harvard University led a study of 323 people in Denmark who were infected with the new coronavirus. That study, published last October, found that even low levels of PFBA — a PFAS chemical that lodges in the lungs — were associated with more severe symptoms of Covid-19.

Grandjean concluded that more work is needed on the topic, especially with people who have higher PFAS concentrations in their blood.

The new federal study intends to fill that gap and more, looking not only at Covid-19 but viral illnesses like pneumonia and the flu. An ATSDR spokesperson told Circle of Blue that the evaluation would include self-reported symptoms as well as illnesses confirmed by laboratory tests.

Another benefit will be the sample size — 3,300 adults and 775 children — which, if all agree to participate, could be more than 10 times larger than the Denmark study.

“Having more people in a study provides more statistical power for us to be able to distinguish or evaluate links between an exposure and a health effect,” Schaider said. “So having several thousand people as compared to several hundred people should be able to provide more information and assess those links more thoroughly.”


Japan set to release Fukushima plant water into sea

Photo taken on Feb. 13, 2021, from a Kyodo News helicopter shows tanks storing treated radioactive water behind reactor buildings at the Fukushima Daiichi nuclear power plant. (Kyodo)

The Japanese government is poised to release treated radioactive water accumulated at the crippled Fukushima nuclear plant into the sea despite opposition from fishermen, sources familiar with the matter said Friday.

It will hold a meeting of related ministers as early as Tuesday to formally decide on the plan, a major development following over seven years of discussions on how to discharge the water used to cool down melted fuel at the Fukushima Daiichi plant.

The treated water containing radioactive tritium, a byproduct of nuclear reactors, is said to pose little risk to human health because even if one drinks the water, so long as the tritium concentration is low, the amounts of tritium would not accumulate in the body and would soon be excreted.

There is also no risk of external exposure even if the water comes in contact with skin.

Still, concerns remain among Japan’s fisheries industry and consumers as well as neighboring countries such as South Korea and China.

The government has said it cannot continue postponing a decision on the disposal issue, given that the storage capacity of water tanks at the Fukushima complex is expected to run out as early as fall next year.

It asserts that space needs to be secured on the premises, such as for keeping melted fuel debris that will be extracted from the damaged reactors, to move forward with the decades-long process of scrapping the complex.

Plant operator Tokyo Electric Power Company Holdings Inc. says it will take around two years for the discharge to start.

The government had initially hoped to make a decision on the discharge of the treated water in October last year but later decided it would need more time for discussions amid concerns about reputational damage to marine products.

But Prime Minister Yoshihide Suga said Wednesday his government will decide “in a few days” whether to release the water after meeting with Hiroshi Kishi, head of the national federation of fisheries cooperatives, who conveyed his organization’s continued strong opposition to the plan.

On media reports that Japan is poised to discharge the water into the sea, China and South Korea responded by calling on Tokyo to consider it carefully and with transparency.

China urged Japan to make a cautious decision on the matter, saying, “The radioactive material leakage caused by the Fukushima nuclear accident in Japan has had a profound impact on the marine environment, food safety and human health.”

The Japanese government should disclose adequate information and “make a careful decision based on full consultation with neighboring countries,” Chinese Foreign Ministry Spokesman Zhao Lijian told reporters in Beijing.

South Korea’s Foreign Ministry said in a statement, “Our government has always emphasized that the Japanese government needs to transparently open up information over how it deals with contaminated water.”

The ministry added it wants to continue to have close discussions on the issue with Japan and other countries concerned as well with international organizations like the International Atomic Energy Agency.

China and South Korea are among 15 countries and regions that continue to restrict imports of Japanese agricultural and fishery products more than 10 years after the Fukushima nuclear crisis, caused by a devastating earthquake and tsunami in 2011.

In February last year, a government panel proposed various options for disposing of the water, including releasing it into the ocean as well as evaporating it.

The following month, TEPCO drafted a plan to dilute the water to below the legal limit for concentration of radioactive materials before releasing it in the sea.

The Fukushima Daiichi plant, which suffered core meltdowns following the natural catastrophe in March 2011, continues to generate massive amounts of radiation-tainted water after it is used to cool melted fuel.

The water is treated using an advanced liquid processing system, or ALPS, to remove most contaminants and stored in tanks on the complex premises. The process, however, cannot remove tritium, a radioactive byproduct of nuclear reactors.

The IAEA has backed the Japanese government’s plan to dispose of the water, saying releasing it into the sea meets global standards of practice in the nuclear industry.

The Geneva-based body’s Director General Rafael Grossi, during his visit to the Fukushima complex in February, said it is a common way to release water at nuclear power plants, even when they are not in emergency situations.

Japan’s industry minister Hiroshi Kajiyama said to Grossi in a videoconference last month that Japan wants the IAEA to conduct a scientific and objective review of the method of disposal of the water and openly convey its view to the international community.

Kajiyama said at the time that the IAEA’s message is vital in dispelling concerns and reputational worries over the safety of the water that exist domestically as well as in the neighboring countries.


64% of global agricultural land at risk of pesticide pollution?

The study, published in Nature Geoscience, produced a global model mapping pollution risk caused by 92 chemicals commonly used in agricultural pesticides in 168 countries.

The study examined risk to soil, the atmosphere, and surface and ground water.

The map also revealed Asia houses the largest land areas at high risk of pollution, with China, Japan, Malaysia, and the Philippines at highest risk. Some of these areas are considered “food bowl” nations, feeding a large portion of the world’s population.

University of Sydney Research Associate and the study’s lead author, Dr Fiona Tang, said the widespread use of pesticides in agriculture — while boosting productivity — could have potential implications for the environment, human and animal health.

“Our study has revealed 64 percent of the world’s arable land is at risk of pesticide pollution. This is important because the wider scientific literature has found that pesticide pollution can have adverse impacts on human health and the environment,” said Dr Tang.

Pesticides can be transported to surface waters and groundwater through runoff and infiltration, polluting water bodies, thereby reducing the usability of water resources.

“Although the agricultural land in Oceania shows the lowest pesticide pollution risk, Australia’s Murray-Darling basin is considered a high-concern region both due to its water scarcity issues, and its high biodiversity,” said co-author Associate Professor Federico Maggi from the School of Civil Engineering and the Sydney Institute of Agriculture.

“Globally, our work shows that 34 percent of the high-risk areas are in high-biodiversity regions, 19 percent in low-and lower-middle-income nations and five percent in water-scarce areas,” said Dr Tang.

There is concern that overuse of pesticides will tip the balance, destabilise ecosystems and degrade the quality of water sources that humans and animals rely on to survive.

The future outlook

Global pesticide use is expected to increase as the global population heads towards an expected 8.5 billion by 2030.

“In a warmer climate, as the global population grows, the use of pesticides is expected to increase to combat the possible rise in pest invasions and to feed more people,” said Associate Professor Maggi.

Dr Tang said: “Although protecting food production is essential for human development, reducing pesticide pollution is equivalently crucial to protect the biodiversity that maintains soil health and functions, contributing towards food security.”

Co-author Professor Alex McBratney, Director of the Sydney Institute of Agriculture at the University of Sydney, said: “This study shows it will be important to carefully monitor residues on an annual basis to detect trends in order to manage and mitigate risks from pesticide use.”

“We recommend a global strategy to transition towards a sustainable, global agricultural model that reduces food wastage while reducing the use of pesticides,” said the authors of the paper.

FOR MORE INFORMATION: University of Sydney

Stanford study reveals a deepening water crisis in Jordan – and a way forward

Dwindling water supplies and a growing population will halve per capita water use in Jordan by the end of this century. Without intervention, few households in the arid nation will have access to even 40 liters (10.5 gallons) of piped water per person per day.

Low-income neighborhoods will be the hardest hit, with 91 percent of households receiving less than 40 liters daily for 11 consecutive months per year by 2100.

Those are among the sobering predictions of a peer-reviewed paper by an international team of 17 researchers published March 29 in Proceedings of the National Academy of Sciences.

Jordan’s deepening water crisis offers a glimpse of challenges that loom elsewhere as a result of climate change, population growth, intensifying water use, demographic shocks and heightened competition for water across boundaries, said study co-author and Stanford hydrologist Steve Gorelick, who directs the Global Freshwater Initiative at Stanford’s Woods Institute for the Environment. The World Health Organization estimates half of humanity may live in water-stressed areas by 2025, and the United Nations anticipates water scarcity could displace 700 million people by 2030.

In Jordan, flows in the region’s biggest river system — the Jordan-Yarmouk — have declined as a result of upstream diversion in Israel and Syria. Groundwater levels in some areas have dropped by more than 1 meter per year, and a major aquifer along Jordan’s boundary with Saudi Arabia is heavily pumped on both sides of the border.

Demand for water has climbed largely because of population growth punctuated by waves of refugees, including more than 1 million Syrian refugees in the past decade.

Extreme water scarcity and wide disparities in public water supplies are potent ingredients for conflict. Jordan’s water situation — long deemed a crisis — is now on the brink of “boiling over” into instability, said lead study author Jim Yoon, a water security and resilience scientist at Pacific Northwest National Laboratory.

“Jordan’s unique role as a bastion of peace in the region makes these findings all the more cause for concern,” said Yoon, who began work on the study as a PhD student at Stanford University.

The U.N. has committed to ensuring sustainable freshwater management and universal access to clean water and sanitation as one of its 17 sustainable development goals. But until now, analytic frameworks have been lacking, said Gorelick, who led the Jordan Water Project and its continuation, the FUSE Project (Food-water-energy for Urban Sustainable Environments).

The new predictions derive from a first-of-its-kind computer model of Jordan’s freshwater system that simulates interactions among natural processes and human behaviors. Under a range of climate and socioeconomic scenarios, the researchers quantified the effects of maintaining status quo versus introducing measures such as fixing leaky pipes, eliminating water theft, raising tariffs for big water users and reallocating a quarter of water from farms to cities.

The team’s modeling suggests efforts to simultaneously increase supply, slash demand and reform distribution are likely to deliver “exponential” improvements in national water security.

Access to Jordan’s public water supply today is highly unequal, with wealthier households and firms often supplementing rationed municipal supplies with costly deliveries from private tanker truck operators. German economist and study co-author Christian Klassert said, “Avoiding large disparities in public water supply will be necessary to avoid water stress under growing water scarcity in Jordan and regions around the world.”

The many facets of Jordan’s water crisis make it an especially valuable place to explore the impacts of individual versus simultaneous interventions, Gorelick said. Now that a model exists for this complex environment, it can be adapted with relative ease to other regions.

The single most effective step Jordan can take is to increase supply through large-scale desalination. One proposal among many Jordan has pursued to this end since the 1960s would desalinate water from the Red Sea in the south, transport freshwater north to the capital city Amman and dispose of the leftover highly saline water in the rapidly shrinking Dead Sea.

While water policy debates often present selected supply and demand interventions as opposing alternatives, the authors write, suites of interventions in both modes actually work best in concert.

“You would think that any one of these interventions would have a greater impact. But it turns out you have to do everything,” Gorelick said.

For a country whose economic output per person is less than one-tenth that of the U.S., the scale and cost of near-total reform of its water sector are particularly daunting. “In water-scarce regions where sustainability planning is most needed, it is challenging to think beyond how to distribute scarce freshwater tomorrow, next month, and to some extent, in the next several years,” Gorelick said. “It’s in these places where our long-term policy evaluations are most valuable.”

FOR MORE INFORMATION: Stanford University

Even small levels of nitrate in drinking water results in smaller babies

Full Disclosure | EWG

It appears that the weight of newborn babies decreases if even small amounts of nitrates are present in the drinking water that mothers drink before and during pregnancy. This is shown by a major new register-based study carried out by researchers at the universities in Aarhus and Chicago, USA. They now question whether the threshold value is too high.

The more nitrate there is in mothers’ drinking water, the smaller the babies they give birth to. But alarmingly, the declining birth weight can also be registered when the women are exposed to nitrate levels below the EU’s threshold of 50 milligrams of nitrate per litre.

This is shown by a register-based study of more than 850,000 births in Denmark carried out in a Danish-American partnership led by Professor Torben Sigsgaard from the Department of Public Health at Aarhus University and Professor Leslie Stayner and Dr. Vanessa Coffman from the Division of Epidemiology and Biostatistics at the University of Illinois at Chicago, School of Public Health.

On the basis of Danish registry data, the research group concluded that babies born to mothers whose drinking water contains between 25 and 50 milligrams of nitrates per litre — i.e. from half of the current threshold value up to the maximum limit — on average weigh ten grams less than babies born to mothers with smaller amounts of nitrate in the tap water. Not only did the babies weigh less, they were also slightly shorter, while their head size was unaffected by the amount of nitrate — which is the form of nitrogen run off from the agricultural sector that most frequently appears in groundwater.

According to Professor Torben Sigsgaard from Aarhus University, it is difficult to say whether we should be concerned about public health in areas with high amounts of nitrate:

“The difference in body length and weight doesn’t sound like much at first as it’s on average only ten grams, but this is not insignificant if the newborn also begins life as underweight for other reasons. Birth weight is generally recognised as having a life-long impact on a person’s health and development,” says Torben Sigsgaard.

“There is no doubt that the results of the study challenge the threshold value that is in place throughout the Western world, and that any changes will be a bit like turning around a supertanker. But it’s important to discuss these results,” he adds with reference to the WHO, EU and American authorities who all view drinking water as harmful when the content of nitrates is higher than fifty milligrams per litre.

The study was initiated because it has long been known that very high nitrate concentrations may lead to people being exposed to nitrite. This inhibits the body’s ability to absorb oxygen and can lead to the dangerous blue-baby syndrome, or methemoglobinemia to give it its medical name. Nitrate in drinking water is also suspected of causing other chronic diseases, including bowel cancer. Research has also documented how, depending on local geological and geochemical conditions in theearth, the fertiliser used in agriculture more or less percolates down to the groundwater.

“With the study, we’ve established that there is a need to explore the effect of the low nitrate concentrations in the drinking water, if we’re to assess the adequacy of the current threshold values — and this is possible thanks to the unique Danish registers. It wouldn’t be possible to carry out corresponding studies on the basis of US data alone, because such data simply doesn’t exist,” says Torben Sigsgaard.

The research results — more information

The register-based study compares data from more than 850,000 births in Denmark during the period 1991-2011 including the weight, height and head size of the newborn babies — before in turn comparing this with the content of nitrate in drinking water via the parents’ place of residence and the GEUS Jupiter register, which contains information about the quality of drinking water in Danish households based on more than 300,000 nitrate samples from routine water quality monitoring. GEUS stands for Geological Survey of Denmark and Greenland.

Vanessa Coffman and Leslie Stayner from the University of Illinois, Chicago (UIC) and Jörg Schullehner and Birgitte Hansen from GEUS, were important partners on the project. Additional contributions came from colleagues at Aarhus University, including the “Drinking water group” under the Center for Integrated Register-based Research (CIRRAU), as well as researchers from the University of Copenhagen.

The study is financed by the National Institute of Environmental Health Sciences (NIEHS), USA.

Journal Reference:

  1. Vanessa R. Coffman, Anja Søndergaard Jensen, Betina B. Trabjerg, Carsten B. Pedersen, Birgitte Hansen, Torben Sigsgaard, Jørn Olsen, Inger Schaumburg, Jörg Schullehner, Marie Pedersen, Leslie T. Stayner. Prenatal Exposure to Nitrate from Drinking Water and Markers of Fetal Growth Restriction: A Population-Based Study of Nearly One Million Danish-Born ChildrenEnvironmental Health Perspectives, 2021; 129 (2): 027002 DOI: 10.1289/EHP7331


MIT engineers make filters from tree branches to purify drinking water

Xylem tissue in gymnosperm sapwood

The interiors of nonflowering trees such as pine and ginkgo contain sapwood lined with straw-like conduits known as xylem, which draw water up through a tree’s trunk and branches. Xylem conduits are interconnected via thin membranes that act as natural sieves, filtering out bubbles from water and sap.

MIT engineers have been investigating sapwood’s natural filtering ability, and have previously fabricated simple filters from peeled cross-sections of sapwood branches, demonstrating that the low-tech design effectively filters bacteria.

Now, the same team has advanced the technology and shown that it works in real-world situations. They have fabricated new xylem filters that can filter out pathogens such as E. coli and rotavirus in lab tests, and have shown that the filter can remove bacteria from contaminated spring, tap, and groundwater. They also developed simple techniques to extend the filters’ shelf-life, enabling the woody disks to purify water after being stored in a dry form for at least two years.

The researchers took their techniques to India, where they made xylem filters from native trees and tested the filters with local users. Based on their feedback, the team developed a prototype of a simple filtration system, fitted with replaceable xylem filters that purified water at a rate of one liter per hour.

Their results, published today in Nature Communications, show that xylem filters have potential for use in community settings to remove bacteria and viruses from contaminated drinking water.

The researchers are exploring options to make xylem filters available at large scale, particularly in areas where contaminated drinking water is a major cause of disease and death. The team has launched an open-source website, with guidelines for designing and fabricating xylem filters from various tree types. The website is intended to support entrepreneurs, organizations, and leaders to introduce the technology to broader communities, and inspire students to perform their own science experiments with xylem filters.

“Because the raw materials are widely available and the fabrication processes are simple, one could imagine involving communities in procuring, fabricating, and distributing xylem filters,” says Rohit Karnik, professor of mechanical engineering and associate department head for education at MIT. “For places where the only option has been to drink unfiltered water, we expect xylem filters would improve health, and make water drinkable.”

Karnik’s study co-authors are lead author Krithika Ramchander and Luda Wang of MIT’s Department of Mechanical Engineering, and Megha Hegde, Anish Antony, Kendra Leith, and Amy Smith of MIT D-Lab.

Clearing the way

In their prior studies of xylem, Karnik and his colleagues found that the woody material’s natural filtering ability also came with some natural limitations. As the wood dried, the branches’ sieve-like membranes began to stick to the walls, reducing the filter’s permeance, or ability to allow water to flow through. The filters also appeared to “self-block” over time, building up woody matter that clogged the conduits.

Surprisingly, two simple treatments overcame both limitations. By soaking small cross-sections of sapwood in hot water for an hour, then dipping them in ethanol and letting them dry, Ramchander found that the material retained its permeance, efficiently filtering water without clogging up. Its filtering could also be improved by tailoring a filter’s thickness according to its tree type.

The researchers sliced and treated small cross-sections of white pine from branches around the MIT campus and showed that the resulting filters maintained a permeance comparable to commercial filters, even after being stored for up to two years, significantly extending the filters’ shelf life.

The researchers also tested the filters’ ability to remove contaminants such as E. coli and rotavirus — the most common cause of diarrheal disease. The treated filters removed more than 99 percent of both contaminants, a water treatment level that meets the “two-star comprehensive protection” category set by the World Health Organization.

“We think these filters can reasonably address bacterial contaminants,” Ramchander says. “But there are chemical contaminants like arsenic and fluoride where we don’t know the effect yet,” she notes.


Encouraged by their results in the lab, the researchers moved to field-test their designs in India, a country that has experienced the highest mortality rate due to water-borne disease in the world, and where safe and reliable drinking water is inaccessible to more than 160 million people.

Over two years, the engineers, including researchers in the MIT D-Lab, worked in mountain and urban regions, facilitated by local NGOs Himmotthan Society, Shramyog, Peoples Science Institute, and Essmart. They fabricated filters from native pine trees and tested them, along with filters made from ginkgo trees in the U.S., with local drinking water sources. These tests confirmed that the filters effectively removed bacteria found in the local water. The researchers also held interviews, focus groups, and design workshops to understand local communities’ current water practices, and challenges and preferences for water treatment solutions. They also gathered feedback on the design.

“One of the things that scored very high with people was the fact that this filter is a natural material that everyone recognizes,” Hegde says. “We also found that people in low-income households prefer to pay a smaller amount on a daily basis, versus a larger amount less frequently. That was a barrier to using existing filters, because replacement costs were too much.”

With information from more than 1,000 potential users across India, they designed a prototype of a simple filtration system, fitted with a receptacle at the top that users can fill with water. The water flows down a 1-meter-long tube, through a xylem filter, and out through a valve-controlled spout. The xylem filter can be swapped out either daily or weekly, depending on a household’s needs.

The team is exploring ways to produce xylem filters at larger scales, with locally available resources and in a way that would encourage people to practice water purification as part of their daily lives — for instance, by providing replacement filters in affordable, pay-as-you-go packets.

“Xylem filters are made from inexpensive and abundantly available materials, which could be made available at local shops, where people can buy what they need, without requiring an upfront investment as is typical for other water filter cartridges,” Karnik says. “For now, we’ve shown that xylem filters provide performance that’s realistic.”

Journal Reference:

  1. Krithika Ramchander, Megha Hegde, Anish Paul Antony, Luda Wang, Kendra Leith, Amy Smith, Rohit Karnik. Engineering and characterization of gymnosperm sapwood toward enabling the design of water filtration devicesNature Communications, 2021; 12 (1) DOI: 10.1038/s41467-021-22055-w

FOR MORE INFORMATION:  Massachusetts Institute of Technology

‘Climbing droplets’ could lead to more efficient water harvesting

Dr. Xianming Dai, assistant professor of mechanical engineering in the Erik Jonsson School of Engineering and Computer Science, and his research team have been working to develop technology that harvests clean water from the air without using external energy.

University of Texas at Dallas researchers have discovered that a novel surface they developed to harvest water from the air encourages tiny water droplets to move spontaneously into larger droplets.

When researchers placed microdroplets of water on their liquid-lubricant surface, the microdroplets propelled themselves to climb, without external force, into larger droplets along an oily, ramp-shaped meniscus that forms from the lubricant around the larger droplets. The “coarsening droplet phenomenon” formed droplets large enough for harvesting.

“This meniscus-mediated climbing effect enabled rapid coalescence on hydrophilic surfaces and has not been reported before. We have discovered a new physical phenomenon that makes it possible to harvest water more rapidly from air without external force,” said Dr. Xianming Dai, assistant professor of mechanical engineering in the Erik Jonsson School of Engineering and Computer Science, who led the work. “If we don’t have this new phenomenon, the droplets would be too small, and we could hardly collect them.”

Microdroplets of water on a hydrophilic SLIPS surface (left) propel themselves to climb, without external force, into larger droplets along an oily, ramp-shaped meniscus that forms from the lubricant around the larger droplets. On the right, the video clip shows how microdroplets behave on a solid slippery surface.

The findings, published March 25 in Cell Reports Physical Science, could solve key problems in harvesting water from air. Many droplets that condense from water vapor in the air are too small to be collected, and they can cover a surface in a way that impedes further condensation.

Developing new technologies that harvest water from the atmosphere is a growing field of research as more and more people live in areas where fresh water is in short supply. Scientists estimate that 4 billion people live in regions with severe freshwater shortages for at least one month each year. This number is predicted to rise to between 4.8 billion and 5.7 billion by 2050. Reasons include climate change, polluted water supplies and increased demand due to both population growth and changes in usage behavior.

The key to the microdroplet’s self-climbing action is a surface that Dai and his colleagues previously developed. Their liquid lubricant, a hydrophilic slippery liquid-infused porous surface (SLIPS), has a unique hydrophilic nature for water harvesting and rapidly directs water droplets into reservoirs.

Researchers discovered the self-propelling droplet phenomenon on their surface by accident. They were testing different lubricants to determine which could best facilitate water harvesting when they saw the smaller water droplets propel themselves into larger droplets. That led them to collaborate with Dr. Howard A. Stone, chair of mechanical and aerospace engineering at Princeton University and an expert in fluid dynamics, to investigate the underlying physics of the phenomenon.

“Dr. Dai and his team led this work. The ideas are creative, and they made a series of observations in the laboratory that allowed them to understand the underlying physics and its potential applications,” Stone said. “They reached out to me to discuss the mechanism, and we had several Skype or Zoom meetings and email exchanges. It was all very interesting and stimulating. I enjoyed very much seeing the ideas evolve into the published paper.”

As water vapor condenses on the liquid-lubricant surface, oil from the lubricant forms a meniscus, or curvature, around the droplets. The meniscus looks like an upward-curving ramp, which acts like a bridge along which microdroplets spontaneously climb toward and coalesce with larger water droplets, a process the researchers call the coarsening effect. The properties of the lubricated surface prevent the water droplets from being completely submerged in the oil, so they can float on the oil, allowing them to climb.

“The oil meniscus acts like a bridge, so the droplet can climb on it,” Dai said. “The small droplet actively looks for a larger one. After they are connected by the bridge, they become one.”

As tiny water droplets condense from air on a cooled surface, they become thermal barriers that prevent further condensation. By allowing for rapid water droplet collection, the coarsening droplets help clear surfaces for new droplets to form, which facilitates faster, more efficient water harvesting.

The self-propelled coarsening droplet on hydrophilic SLIPS shows rapid removal of condensed submicrometer-sized droplets regardless of how the surface is oriented, which presents a promising approach compared to other surfaces used for water harvesting.

“We cannot harvest a large amount of water unless we have a rapid harvesting process. The problem with other surfaces is that the small water droplets may evaporate before they can be harvested,” Dai said.

“Based on our experimental data, the coarsening surface enhanced the water harvesting rate 200% higher than its counterparts,” said Zongqi Guo, a mechanical engineering doctoral student and co-lead author. Dai and his colleagues continue to work on ways to use their lubricant to make sustainable water harvesting systems that are mobile, smaller in size, lower in weight and less expensive.

“If we can do that, we can harvest water anywhere that has air, which is particularly important in regions where water is scarce,” Dai said.

The research was funded by the National Science Foundation and the Army Research Office.

Journal Reference:

  1. Zongqi Guo, Lei Zhang, Deepak Monga, Howard A. Stone, Xianming Dai. Hydrophilic slippery surface enabled coarsening effect for rapid water harvestingCell Reports Physical Science, 2021; 100387 DOI: 10.1016/j.xcrp.2021.100387

FOR MORE INFORMATION: University of Texas at Dallas

Hopes Low for Progress at India, Pakistan’s First River-Sharing Talks in Three Years


NEW DELHI (Reuters) – An Indian official played down on Tuesday prospects for a breakthrough at the first talks in three years with neighbouring Pakistan aimed at resolving long-running disputes over hydroelectric projects on the shared Indus River.

Pakistan is concerned that India’s plans for hydroelectric plants in the disputed Himalayan region of Kashmir will damage the flow of the river, which feeds 80% of its irrigated agriculture, along with tributaries.

India has defended the construction of its Pakal Dul and Lower Kalnai dams, saying they are allowed by the Indus Water Treaty brokered by the World Bank.

“It is our job to find a middle path. But to say we can achieve something is maybe a bit too optimistic,” an Indian official involved in the talks in New Delhi told Reuters.

“There are many things on which we can’t compromise,” added the official, who spoke on condition of anonymity because of the sensitive nature of the discussions.

India issued no statement on the talks, which are set to end on Wednesday.

The talks come after a gap of three years because of tension over Kashmir, the Muslim-majority territory both south Asian nations claim in full.

In recent weeks, the nuclear-armed rivals have taken tentative steps to improve ties, such as a rare military pact last month to stop firing on the Kashmir border that has killed scores of civilians.

FOR MORE INFORMATION: https://www.usnews.com/news/world/articles/2021-03-23/hopes-low-for-progress-at-india-pakistans-first-river-sharing-talks-in-three-years