Tag Archives: freshwater

Climate change might mean more rain, but less water for everybody

In a hotter future, plants will consume more water than they do today — which means a drier future despite the anticipated increases in precipitation.

Climate heating is estimated to increase precipitation levels in places like the United States and Europe through the generation of more water vapor and weather pattern disruptions. However, humans may find themselves in a net drier future, a new paper explains: as the climate changes, crops and wild plants will use up more water in these areas.

More supply, much more demand

“Approximately 60% of the global water flux from the land to the atmosphere goes through plants, called transpiration. Plants are like the atmosphere’s straw, dominating how water flows from the land to the atmosphere. So vegetation is a massive determinant of what water is left on land for people,” explained lead author Justin S. Mankin, an assistant professor of geography at Dartmouth.

“The question we’re asking here is, how do the combined effects of carbon dioxide and warming change the size of that straw?”

Led by scientists at Dartmouth College, the paper notes a drier future for people in areas that are already facing water stress despite anticipated increases in precipitation levels.

The prevailing theory up to this study was that the increase in CO2 gas in the atmosphere will lead to reduced water consumption in plants — which would ultimately mean more water in streams and rivers. The underlying mechanism is that higher concentrations of CO2 allow plants to perform photosynthesis with greater water efficiency, as they can close off some of their pores (stomata) on their leaves. These pores shuttle CO2 molecules inside leaves, but also bleed out water through evaporation while they are open. All the water they don’t take, the logic goes, will instead percolate through the ground and into groundwater reserves.

This assumption isn’t wrong; however, it’s only accurate to the tropics and the extremely high latitudes, where freshwater is plentiful and competition for it is low. For most areas of the mid-latitudes, the team explains, plant responses to climate change will make the land drier, not wetter.

The researchers used climate modeling to analyze how freshwater availability will shift under our current projections of climate change and the ways precipitation will be divided among plants, rivers, and soils. They used a new, self-developed method to partition future precipitation and to calculate runoff in a warmer climate with higher levels of atmospheric carbon dioxide.

All in all, the team reports that as carbon dioxide levels rise in the atmosphere, plants will indeed take in less water, which will make the land wetter. However, warmer climates will mean a longer and warmer growing season. So, after the initial wet period, plants will actually start drying out the land (as they grow for longer than before). As CO2 levels keep increasing and mean temperatures keep rising after this second phase, plants are likely to grow even more (as photosynthesis is further amplified).

In some areas of the world, the water burden of the latter two factors (longer growing seasons and stronger photosynthesis) will out-pace gains from closing stomata, meaning that vegetation will, overall, consume more water than before. Vast swathes of mid-latitude lands will have less water in the soil and less water draining into streams, despite the projected increase in precipitation and plant water-efficiency.

So why is this a problem? Well, fresh water is essential for life, be it humans, animals, plants, or everything smaller. Our industries also depend on it. However, it is a limited resource, both in quantity and supply. Many areas of the world receive most precipitation during the cold part of the year (around winter) but consume most during the warm period (summer).

“Throughout the world, we engineer solutions to move water from point A to point B to overcome this spatiotemporal disconnect between water supply and its demand. Allocating water is politically contentious, capital-intensive and requires really long-term planning, all of which affects some of the most vulnerable populations,” Mankin adds.

“Our research shows that we can’t expect plants to be a universal panacea for future water availability. So, being able to assess clearly where and why we should anticipate water availability changes to occur in the future is crucial to ensuring that we can be prepared,”

The paper “Mid-latitude freshwater availability reduced by projected vegetation responses to climate change” has been published in the journal Nature Geoscience.

This map depicts a time series of data collected by NASA's Gravity Recovery and Climate Experiment (GRACE) mission from 2002 to 2016, showing where freshwater storage was higher (blue) or lower (red) than the average for the 14-year study period. Credit: NASA.

Human activity is messing with global freshwater movement

This map depicts a time series of data collected by NASA's Gravity Recovery and Climate Experiment (GRACE) mission from 2002 to 2016, showing where freshwater storage was higher (blue) or lower (red) than the average for the 14-year study period. Credit: NASA.

This map depicts a time series of data collected by NASA’s Gravity Recovery and Climate Experiment (GRACE) mission from 2002 to 2016, showing where freshwater storage was higher (blue) or lower (red) than the average for the 14-year study period. Credit: NASA.

The world’s wetlands are getting wetter and dry areas are growing drier due to human water management, climate change, and natural cycles. This is the conclusion of a new study, first to combine NASA satellite observations with data on human activity, mapping the two together.

Researchers led by Matt Rodell of NASA’s Goddard Space Flight Center in Greenbelt, Maryland, analyzed 14 years worth of data gathered by the Gravity Recovery and Climate Experiment (GRACE) spacecraft mission, whose primary objective is tracking global trends in freshwater in 34 regions around the world. GRACE consists of twin satellites that, since 2002, have been measuring the distance between themselves in order to detect changes in Earth’s gravity field caused by movements of mass below. Using this method, GRACE tracked variations in terrestrial water movements until the mission ended in October 2017.

In order to understand freshwater movement trends on a global level, the team also employed other datasets, like the Global Precipitation Climatology Project and Geological Survey Landsat.

“This is the first time that we’ve used observations from multiple satellites in a thorough assessment of how freshwater availability is changing, everywhere on Earth,” said Rodell in a statement. “A key goal was to distinguish shifts in terrestrial water storage caused by natural variability – wet periods and dry periods associated with El Niño and La Niña, for example – from trends related to climate change or human impacts, like pumping groundwater out of an aquifer faster than it is replenished.”

According to the authors, we are witnessing major hydrologic change around the world. Trends suggest that wetland areas are getting wetter while dry areas, typically found between the tropics and high latitudes, are getting drier due to groundwater depletion.

In some regions, water loss is clearly driven by climate change, for example, the Arctic due to ice sheets melting or in mountain areas due to alpine glacier melt. More time and data will have to be required, however, in order to determine the driving forces behind other patterns of freshwater change.

Freshwater loss from ice sheets raises sea levels, threatening coastlines and small islands around the world. On land, losing freshwater can have severe repercussions both for wildlife and human communities. For instance, Southwestern California lost 4 gigatons of freshwater per year from 2007 to 2015, during the worst drought in 1,200 years.

“We know for sure that some of these impacts are caused by climate change,” said Rodell, chief of the Hydrological Sciences Laboratory at NASA. “We are using huge parts of the [Earth’s] available water.”

However, there were also areas that experienced an increase in freshwater circulation, such as the Okavango Delta region in southern Africa, which saw improvements from increased rainfall, or Saudi Arabia, which ended a wheat farming program in 2015, leading to an increase in available water.

Credit: Rodell et al, 2018.

Credit: Rodell et al, 2018.

Elsewhere, assessing freshwater flow proved more complicated. Take, for instance, Xinjiang province in northwestern China. The province, which is about the size of Kansas, is bordered by Kazakhstan to the west, the Taklamakan desert to the south, and encompasses the central portion of the Tien Shan Mountains. Xinjiang lost 5.5 gigatons of terrestrial water storage per year but the initial assumption — that less rainfall was to blame — didn’t hold water. Instead, the researchers found that a combination of an increase in water consumption for crop irrigation and evaporation of river water from the desert floor was a more likely explanation for the observed patterns.

The biggest takeaway from the study, however, is the huge footprint humans are leaving on global freshwater circulation due to our massive engineering infrastructures. The new map compiled by NASA documents the consequences of the filling of major reservoirs, like the one bound by the massive Three Gorges Dam in China, of the diverted rivers in India, and of the exploitation of the High Plains aquifer in the central United States for agriculture.

Water is the world’s most precious resource, and we need to treat it with more respect if we’re to live in peace and prosperity on this planet. The message is clear: we need to act now.

The GRACE mission will continue once GRACE Follow-On launches on May 19 from Vandenberg Air Force Base in California.

Scientific reference: “Emerging Trends in Global Freshwater Availability,” Matthew Rodell, James Famiglietti, David Wiese, J.T. Reager, Hiroko Beaudoing, Felix Landerer and Min-Hui Lo, was published in the journal Nature on May 17, 2018.

Credit: Max Pixel.

New desalinization technique separates seawater into freshwater and lithium

A new desalinization technique can not only turn seawater into delicious freshwater but also recover lithium ion for use in batteries.

Credit: Max Pixel.

Credit: Max Pixel.

You might have come across the viral story that follows Cape Town’s impending water crisis, which threatens millions. The South African city isn’t alone — it’s a heartbreaking story, but it’s just one of many other cases happening due to poor water management and unsustainable usage.

Earth, the pale blue dot, looks like a watery paradise from outer space. It sounds ludicrous that there isn’t enough water to go around but, despite covering about 70% of the Earth’s surface, water — particularly, drinking water — is not as plentiful as you might think. Only 3% of it is fresh.

Due to population growth, climate change, and human action, global demand for fresh water is expected to exceed supply by 40% in 2030, according to a UN report. Already, over one billion people lack access to drinkable water and another 2.7 billion find it scarce for at least one month of the year.

Bearing all of this in mind, it’s no wonder that many institutions and companies have been wildly experimenting with desalinization farms all over the world, particularly in countries vulnerable to droughts. Some of these projects cross the boundaries between reality and science fiction, such as The Pipe — a solar-powered offshore desalination plant that could serve pure drinkable water directly into a Californian city’s primary water piping.


Typical desalination plant process. 

From salty to fresh in one pass

Researchers at Monash University, the CSIRO, and the University of Texas at Austin think they have a more efficient solution. Instead of relying on external power to drive reverse osmosis pumps, the team is experimenting with a more passive desalinization technique.

A scanning electron microscope image of metal-organic frameworks used to seaparate seawater into freshwater and lithium. Credit: CSIRO.

A scanning electron microscope image of metal-organic frameworks used to separate seawater into freshwater and lithium. Credit: CSIRO.

They developed a membrane based on metal-organic frameworks (MOFs), inspired by the “ion selectivity” of biological cell membranes. The scientists designed their membrane such that the MOFs only dehydrate specific ions that pass through passively, without having the water forced into the membrane, thus saving energy.

“We can use our findings to address the challenges of water desalination. Instead of relying on the current costly and energy-intensive processes, this research opens up the potential for removing salt ions from water in a far more energy efficient and environmentally sustainable way,” Huanting Wang, a professor at Monash, said in a statement.

Not only does the MOF membrane output clean, drinkable water, but it also filters out lithium from the seawater. The lithium stays embedded within the membrane’s spongy structure, ready to be collected. Lithium is in high demand by the electronics industry which requires it for lithium-ion batteries, the kind that power everything from smartphones to Tesla roadsters.

“Also, this is just the start of the potential for this phenomenon. We’ll continue researching how the lithium ion selectivity of these membranes can be further applied. Lithium ions are abundant in seawater, so this has implications for the mining industry who current use inefficient chemical treatments to extract lithium from rocks and brines,” Wang added.

MOFs have a huge internal surface area — the largest of any known material. If you’d unfold a single gram of the material, you could cover an entire football field. Previously, researchers have exploited MOFs’ intricate structure in carbon emission sponges, high-precision sensors, microbial water filters, and even artificial photosynthesis reactors that produce liquid fuels literally out of thin air. 

The same technique could also be employed in other applications, particularly in waste management. The mining industry, for instance, relies on reverse osmosis membranes to reduce water pollution and recover valuable minerals. Likewise, reverse osmosis is used by the industry to filter wastewater in processes like fracking.

“Produced water from shale gas fields in Texas is rich in lithium,” says Benny Freeman, co-author of the study. “Advanced separation materials concepts such as ours could potentially turn this waste stream into a resource recovery opportunity.”

The findings have been published in  Science Advances.

Huge freshwater reserves found beneath oceans

Scientists have found huge reserves of freshwater in a totally unexpected area: several kilometers offshore, beneath the oceans. This new discovery has the potential to avert or at least minimize the effects of the almost certain water crisis some areas of the world will be facing in future years.

New research suggests that half a million cubic kilometers of low-salinity water are buried beneath the seabed on continental shelves around the world. (Credit: © DJ / Fotolia)

A new study published in Nature reveals that an estimated half a million cubic kilometers of low-salinity water are buried beneath the seabed on continental shelves all around the world. The water has been located off Australia, China, North America and South Africa, but it’s very likely that the same can be found in many more areas throughout the world.

“The volume of this water resource is a hundred times greater than the amount we’ve extracted from the Earth’s sub-surface in the past century since 1900,” says lead author Dr Vincent Post (pictured) of the National Centre for Groundwater Research and Training (NCGRT) and the School of the Environment at Flinders University.
“Knowing about these reserves is great news because this volume of water could sustain some regions for decades.”

Geologists have known for some time that freshwater can be found under the seafloor, but they thought that it only occurred under rare and special conditions.

“Our research shows that fresh and brackish aquifers below the seabed are actually quite a common phenomenon,” he says.

These reserves were formed several thousands of years ago (or perhaps even more), when the sea levels were much lower than today and the coastline was further out. Dr. Post explains:

“So when it rained, the water would infiltrate into the ground and fill up the water table in areas that are nowadays under the sea. “It happened all around the world, and when the sea level rose when ice caps started melting some 20,000 years ago, these areas were covered by the ocean. “Many aquifers were — and are still — protected from seawater by layers of clay and sediment that sit on top of them.”

An aquifer is an underground layer of water-bearing permeable rock or unconsolidated materials (gravel, sand, or silt) from which groundwater can be extracted using a water well. Basically, underground aquifers contain water and are isolated from what’s surrounding them by impermeable layers – usually clay.

While offshore drilling can be very costly, many areas of the world are overconsuming water, and, inevitably, the water reserves will start running low. As the resource is becoming scarcer and scarcer, at one point, it may likely become feasible to extract this type of water.

“Freshwater on our planet is increasingly under stress and strain so the discovery of significant new stores off the coast is very exciting. It means that more options can be considered to help reduce the impact of droughts and continental water shortages.

Journal Reference:

  1. Vincent E.A. Post, Jacobus Groen, Henk Kooi, Mark Person, Shemin Ge, W. Mike Edmunds. Offshore fresh groundwater reserves as a global phenomenonNature, 2013; 504 (7478): 71 DOI: 10.1038/nature12858