By Andrew Bach and Bradley Smith

Looking over the edge of the Glines Canyon Dam in February 2012, six months after the dam removal project had started. Photo National Park Service

As the last block of concrete was pulled from the riverbed, the Elwha River in the Olympic Mountains of Washington State flowed freely for the first time in over 100 years. The river was historically one of the most productive salmon streams for its size in the Pacific Northwest. Four hundred thousand salmon once swam its length each year but, in the century since the dam’s construction, that number had fallen to a few thousand.¹ Within months of the dam’s removal, nature has rushed back: over 200 salmon have already returned. The prospect of a river teeming with silverbacked salmon weighing over 45 kilograms each may no longer remain a hazy memory of local Native American tribes.

The Elwha dam removal project stands as one of the first large dams ever removed. The intent of removing the dams is to fully restore the Elwha River ecosystem and its native migratory fish species. In doing so, the Elwha dam project revived the debate of how to balance the conflicting demands of humans for both clean energy and healthy ecosystems. Previously, that debate has been weighted decisively in favor of dam projects. But with a greater understanding of the value of ecosystem services, the Elwha dam project may represent the start of a revolution in how we assess the West’s aging dam infrastructure.²

The Tribe

The Elwha watershed was the traditional homeland of the S’Klallam Tribe, whose culture flourished on salmon from the river, among other natural resources. Against tribal will, construction of the Elwha Dam began in 1910 for the sole purpose of generating the first electricity in the region. The electricity powered several lumber mills and fueled economic development, resulting in construction of a second dam, the Glines Canyon Dam farther upstream, in 1927. The lower Elwha Dam did not have fish passage and the salmon runs declined from 400,000 per year to about 3,000 fish in the lowest eight kilometers of the river. Tributaries in the headwaters of the Elwha River were protected from further development in 1938 with the establishment of Olympic National Park. The impact on the S’Klallam Tribe was devastating for their culture and livelihood. A fishery that could be worth over $10 million was lost. The near disappearance of salmon in the watershed also had a cascading effect on the terrestrial ecosystem, where some 22 species of resident wildlife were affected, and over 90 species of migratory birds. The decomposing salmon carcasses have been shown to significantly contribute to the biomass of the forest itself, accounting for 20–60 percent of riparian biomass.¹

Newly mobilized sediment near Ediz Hook after the Elwha dams were removed. Photo Tom Roorda/USGS

The dams also stopped the movement of sediment through the river system, resulting in deposition in the reservoir deltas.¹ As a result, the river incised its channel, armored its bed with boulders (instead of sand and gravel where salmon could lay eggs), and reduced the sediment delivery to the coastal environment, causing beach erosion for at least 30 kilometers along the shore.³ Some of the most intense erosion occurred on Ediz Hook, which creates an important lumber shipping port at Port Angeles. From the 1970s through the 2000s, the Army Corps of Engineers spent hundreds of millions of dollars each year to protect the Ediz Hook from erosion.

In 1968 the S’Klallam Tribe and numerous environmental groups tried to stage a comeback by opposing relicensing of the dams by the federal government, citing loss of the salmon fishery, negative environmental impacts within the watershed, and submersion of a tribal sacred site under the reservoir.

But despite the strong case against the dam, the local nontribal community strongly favored relicensing it. The electricity from the dams continued to play an important role in powering the region’s timber-based economy. There were additional challenges in assessing the possible impacts of removing the dam, given the amount of sediment that had built up, and on the potential impact on the City of Port Angeles’ water supply. Even a U.S. Department of the Interior study in 1991, which recommended the removal of the dams, failed to energize foot-dragging state officials and local interest groups. The removal was legislated by Congress with the passage of the Elwha River Ecosystem and Fisheries Restoration Act P.L. 102-495.

Federal Laws Kick In

However, in the nearly two decades that followed the passage of the 1992 federal law mandating the dams’ removal and the release of funds to begin work, a generational shift took place. Dams—for so long seen as symbols of development and progress—were increasingly being criticized for their social and environmental impacts. The issue came into focus internationally following protests over the forced evictions of hundreds of thousands of people in India and China due to dam projects. In the United States, aging dam infrastructure was pushing local governments to repair or remove many of these structures. The 85,000 large dams in the United States have an average age of 53 years, and over 4,000 of the large dams are considered structurally unsound.⁴ An additional problem with dams is that, as they age, they fill with sediment, reducing storage capacity.

For these reasons, hundreds of small dams (less than 7.5 meters in height) have been removed in recent decades. With smaller structures, there is little question that rivers can return to their pre-dam flow characteristics.^5,6 Successful dam removals and ecosystem recovery have been seen with the Edwards Dam in Maine, and the Marmot and Condit Dams in Oregon. But as the Elwha dam saga continued to rumble into the new millennium, the question remained whether dam removal would be successful for large structures.

A major concern when removing a dam is managing the remobilized sediments from the lake delta, which are now exposed to flowing water. The Elwha River dams have accumulated over 34 million cubic meters of sediment. The reservoirs of the Glines Canyon and the Elwha Dams had no drains and were too large for a single, explosive removal. Each dam had unique characteristics and required its own removal plans, time frames for safety concerns, and strategies for managing the massive amounts of sediment in the reservoirs. Careless removal of the dams could cause large amounts of sediment in the reservoir deltas to flow down the river.⁷ Even though the Elwha Dam is the older of the two dams, the majority of sediment lay trapped upstream behind Glines Canyon Dam (GCD). Thus, the GCD removal progressed slowly in order to manage the sediment through the river system. Further complicating matters, sediment behind the GCD was located in a federally designated wilderness area of Olympic National Park, where machinery is banned.

In September 2011 work began on removing both dams. The Elwha Dam was structurally unsound, due to poor construction, and required a complex removal process to avoid a catastrophic failure. First, a cofferdam moved the river to the left side of the dam; an artificial channel cut through the bedrock where the dry right spillway is located. Then a second cofferdam directed the river into the artificial channel for removing water from behind the main dam, which was subsequently removed by jackhammering and blasting. By contrast, the Glines Canyon Dam was structurally sound, allowing for a large jackhammer to be used directly on the dam face. Both dams were removed within 13 months. However, the Elwha Dam was removed first, and muddy sediment poured down the river and into the ocean for the first time in over 100 years. Beaches near the river’s mouth experienced immediate growth, even faster than expected. After the Glines Canyon dam was fully breached, even larger amounts of sediment began moving through the river. Logs and other floating debris created logjams, causing the river to erode its banks and migrate across its floodplain as it had before the dams were installed. Sediment levels are expected to return to normal in one to three years.

A First Step

A map of the Elwha River watershed in Washington state, where the country’s first large dam removal project was recently completed. Photo National Park Service

Of course, removing the dam was only the first part of the first step of the real goal of restoring salmon fisheries. During the decade prior to removal, scientists surveyed fish populations in the river to inventory populations of native and migrating fish species.⁷ Fisheries biologists also captured Elwha River fish stock for transport to hatcheries and nearby streams for rearing in order to preserve genetic diversity. The schedule of work during the process of removing dams was periodically halted to protect fish during their seasonal runs, and provided windows for their capture and transport to safe rearing sites. Fish stocks will recover following complete deconstruction of the dams, stabilization of sediment transport, and the recovery of the ecosystem food chain that provides food for juvenile salmon that will grow in the Elwha River before migrating to the ocean. However, even in the short time (less than six months) following removal of the Elwha Dam, some wild salmon found the new habitat and spawned, in spite of turbid water. The premature appearance of the native salmon population is a positive signal forecasting the recovery of the salmon population.

The exposed reservoir lakebed represents another restoration problem. Without vegetation cover, the soft lake sediments are subject to erosion during the rainy season. For approximately 10 years, the Park Service has been collecting and saving native seeds, and rearing plants to revegetate the lakebed. As soon as lake levels were drawn down, crews were planting seeds and seedlings in order to head off invasive species. Luckily, this winter has been mild with few erosive rainstorms, and the seed bank in the sediments produced a nearly continuous cover of vegetation. The invasive species will be monitored in coming years, but the soil was more stable than expected during this first critical year.

The removal of dams on the Elwha River offers a unique opportunity to evaluate the effects of large dam removal and subsequent recovery of formerly productive aquatic ecosystems that supported large populations of salmon and a related complex ecosystem.⁸ Although intentional dam removal of this magnitude is unique, it could become more common as those in the United States and other nations manage an aging system of dams. An essential step in removing both small and large dams is assessing watershed scale features before and after dam removal. A comprehensive plan designed to evaluate the effects of dam removal on existing fish populations, food webs and habitats, sediment flow, and many other factors is essential before removing dams. Now, we are well positioned to see exactly how the system responds.

References

1. Winter, BD & Crain, P. Making the case for ecosystem restoration by dam removal in the Elwha River, Washington.Northwest Science 82, 13–28 (2008).
2. Doyle, MW, Harbor, JM & Stanley, EH. Toward policies and decision-making for dam removal. Environmental Management 31, 453–465 (2003).
3. Duda, JJ, Warwick, JA & Magirl, CS, eds. Coastal Habitats of the Elwha River, Washington: Biological and Physical Patterns and Processes Prior to Dam Removal. U.S. Geological Survey Scientific Investigations Report 2011–5120(2011).
4. American Society of Civil Engineers. 2009 Report Card for America’s Infrastructure (ASCE, New York, 2009).
5. Graf, WL. Damage control: Restoring the physical integrity of America’s rivers. Annals of the Association of American Geographers 91, 1–27 (2001).
6. Bednarek, AT. Undamming rivers: A review of the ecological impacts of dam removal. Environmental Management27, 803–814 (2001).
7. McHenry, ML & Pess, GR. An overview of monitoring options for assessing the response of salmonids and their aquatic ecosystems in the Elwha River following dam removal. Northwest Science 82, 29–47 (2008).
8. Poff, NL, Olden, JD, Merritt, DM & Pepin, DM. Homogenization of regional river dynamics by dams and global biodiversity implications. Proceedings of the National Academy of Sciences 104, 5732–5737 (2007).

Originally published in The Solutions Journal; republished through a Creative Commons-Share Alike license.

Groundwater makes up 98 percent of the Earth's fresh water, providing drinking water to more than 1.5 billion people living in urban areas.

Australian scientists have devised a way to model polluted groundwater with computer simulation – and better protect the Earth’s main fresh water supply.

Researchers at the National Centre for Groundwater Research and Training (NCGRT) have developed a new model to predict where – and how fast – polluted groundwater can move from a contaminated site, allowing water managers to better locate and clean up the water.

This could help defeat an emerging threat beneath all the world’s big cities and stave off a looming global water crisis, says Professor Craig Simmons of NCGRT and Flinders University.

“Groundwater contamination currently affects 140 million people in 70 countries,” says Prof. Simmons. “The water is increasingly polluted by pesticides, leaks from landfills and fuel dumps, residential and factory waste and other industrial contaminants which render it unusable and undrinkable.”

In the case of Australia, he adds, the main threat to our groundwater supplies is salinity, though urban supplies are often contaminated with hydrocarbons from old fuel storages.

“Groundwater makes up 98 percent of the Earth’s fresh water. It provides drinking water to more than 1.5 billion people living in cities, and low-cost water to farmers and rural areas. In some countries, up to 90 per cent of urban groundwater is polluted, so we need to tackle the issues of contamination worldwide urgently.”

When pollutants leak into groundwater, they form a plume that usually follows the normal groundwater flow, Dr Yueqing Xie of NCGRT and Flinders University explains. The plume can then spread out underground and contaminate other aquifers used by households, or leach into and contaminate rivers and lakes.

“The problem is that contaminants from landfill sites or saline disposal basins are often denser than groundwater,” he says. “The plumes formed beneath these sites will follow the groundwater flow, but they will also be drawn downward by gravity to mix with often fresher groundwater below.

“Their patterns of formation and migration are very complex, and until recently we thought their onset and growth were not amenable to prediction.

“These plumes merge or split many times randomly into what are called ‘fingers’ until they reach the bottom,” Dr Xie says. “It also depends on what contaminants are in the plume, how dense the plume is, and the type of sediment or rock they have to pass through. For instance, a dense plume sinks more easily into gravel or sand, than clay.”

“Once these dense plumes enter and mix with the groundwater it has been near impossible to tell where they might end up,” Prof. Simmons adds. “We had started to lose faith in our ability to make good predictions using our very best computer models.”

NCGRT researchers have now developed a model that allows researchers and water managers to more reliably predict where and how fast the contaminated dense plumes will travel.

“Instead of trying to predict every fine detail of the plume as we have in the past, we now look at its overall size, how much contamination or salt it has in it, and how fast it’s sinking into the freshwater,” says Prof. Simmons.

“Using this new approach, we can predict how fast the plume is moving and how far away it may end up from the contaminated site. While we can’t always pin down the exact destination of each and every finger, we now have a much better idea of where the overall plume is heading – and where we can intercept it, to clean it up.”

Having the more reliable predictive model assists in more cost effective monitoring and remediation, he adds.

“This new model and way of looking at the problem is a big step towards better protecting one of humanity’s most precious resources: our main freshwater supply.”

The National Centre for Groundwater Research and Training is an Australian Government initiative, supported by the Australian Research Council and the National Water Commission.

Source: ScienceAlert 

The following is part nine in a series on the National Science Foundation’s Science, Engineering and Education for Sustainability (SEES) investment.  Visit parts one, two, three, four, five, six, seven and eight in this series.

Blue mussels face a threatening wave in this logo for the research team's project. Credit: Jason Ramsey

Imagine trying to pitch a tent in a stiff wind. You just have it secured, when a gale lifts the tent–stakes and all–and carries it away.

That’s exactly what’s happening to a species that’s ubiquitous along the rocky shores of both the U.S. West and East Coasts: the blue mussel.

Mussels make use of what are called byssal threads–strong, silky fibers–to attach to rocks, pilings and other hard substrates. They produce the threads using byssus glands in their feet.

Biologist Michael O'Donnell collects blue mussels on rocky shores at San Juan Island, Wash. Credit: Michael O'Donnell

Now, scientists have discovered, the effects of ocean acidification are turning byssal threads into flimsy shadows of their former selves, leaving mussels tossed about by wind and waves.

At high levels of atmospheric carbon dioxide–levels in line with expected concentrations over the next century–byssal threads become weaker, less able to stretch and less able to attach to rocks, found scientists Emily Carrington, Michael O’Donnell and Matthew George of the University of Washington.

The researchers recently published their results in the journal Nature Climate Change; O’Donnell is the lead author.

Oceans Turning Caustic

Scientist Emily Carrington among blue mussels on southern Maine's rocky shores. Credit: Amy Johnson/Bowdoin College

The pH of the seas in which these and other marine species dwell is declining. The waters are turning more acidic (pH dropping) as Earth’s oceans change in response to increased carbon dioxide in the atmosphere.

As atmospheric carbon rises as a result of human-caused carbon dioxide emissions, carbon in the ocean goes up in tandem, ultimately resulting in ocean acidification, scientists have found.

To study the effects of ocean acidification on marine organisms, Carrington has been awarded an NSF SEES (Science, Engineering, and Education for Sustainability) Ocean Acidification grant.

“We need to understand the chemistry of ocean acidification and its interplay with other marine processes–while Earth’s seas are still hospitable to life as we know it,” says David Garrison, program director in NSF’s Division of Ocean Sciences. “In the rocky intertidal zone, blue mussels are at the heart of those processes.”

Land Between the Tides

Blue mussels anchor to rocks with byssal threads, now affected by ocean acidification. Credit: Emily Carrington/UW

Visit the land between the tides, and you’ll see waves crashing on boulders tinged dusky blue by snapped-closed mussels.

“Their shells are a soft color, the misty blue of distant mountain ranges,” wrote Rachel Carson more than 50 years ago in her best-selling book The Edge of the Sea.

For blue mussels trying to survive, the rocky intertidal zone indeed may be akin to scaling a mountain range.

The rocky intertidal is above the waterline at low tide and underwater at high tide–the area between tide marks.

It’s home to such animals as starfish and sea urchins, and seaweed such as kelp. All make a living from what floats by rocky cliffs and boulders.

It can be a hard go. Rocky intertidal species must adapt to an environment of harsh extremes. Water is available when the tide washes in; otherwise residents of this no man’s land between sea and shore are wide open to the elements.

Waves can dislodge them, and temperatures can run from scalding hot to freezing cold.

Hanging On For Dear Life

In the rocky intertidal, blue mussels hang on for dear life.

That may not always be the case.

To discover the tenacity of mussels, scientists test maximum force needed to pull them free. Credit: Michael O'Donnell

Combining results from laboratory experiments with those from a mathematical model, Carrington and colleagues show that at high carbon dioxide concentrations, blue mussels can be dislodged by wind and wave forces 40 percent lower than what they are able to withstand today.

Mussels with this weakened ability, once dislodged from their homes, could cause ecological shifts in the rocky intertidal zone–and huge economic losses in a global blue mussel aquaculture industry valued at U.S. $1.5 billion each year.

“Mussels are among the most important species on rocky shores worldwide,” says O’Donnell, “dominating ecosystems wherever they live. The properties in their byssal threads are also of interest to biochemists and have been studied as possible medical adhesives.”

Blue mussels may make important contributions to the field of materials science, says Carrington.

“Some species of mussels are experts at gluing onto seagrass, some to other shells, some even adhere to rocks in the harsh conditions of deep-sea hydrothermal vents. Each may have different genes that code for different proteins, so the adhesives vary.”

Will their potential be realized? Carrington, O’Donnell and George have found a disturbing answer.

The scientists allowed mussels to secrete byssal threads in a range of ocean water chemistries from present-day through predicted near-future conditions, then tested the threads to see how strong they were.

At levels considered reasonable for a near-future coastal ocean (given current rates of acidification), byssal threads were less able to stretch and therefore less able to adhere. Further testing revealed that the problem was caused by weakening of the glue where the threads attach to rocks and other hard surfaces.

Ocean Acidification Beyond Shells and Corals

Researchers Matt George, Michael O'Donnell and Rebecca Guenther study water chemistry. Credit: K. Ballard/University of Washington

“Much ocean acidification research has focused on the process of calcification,” says Carrington, “through which animals and some plants make hard parts such as shells.”

In acidifying oceans, marine species that depend on calcium carbonate have a more difficult time forming shells or, in the case of coral reefs, skeletons.

“But there’s more to marine communities than calcified parts,” says O’Donnell. Other species such as mussels and their byssal threads, he says, are equally important.

“Understanding the broader consequences of ocean acidification requires looking at a variety of biological processes in a range of species.”

A need that didn’t exist when Rachel Carson wrote The Edge of the Sea.

“When we go down to the low-tide line, we enter a world that is as old as the Earth itself–the primeval meeting place,” mused Carson, “of the elements of earth and water.”

And of mussels and rock. Fifty years hence, will the mussels still be here?

Source: National Science Foundation

Amphipod genus Leucothoe

When Nova Southeastern University Professor Jim Thomas and his global team of researchers returned to the Madang Lagoon in Papua New Guinea, they discovered a treasure trove of new species unknown to science.

This is especially relevant as the research team consisted of scientists who had conducted a previous survey in the 1990s.

“In the Madang Lagoon, we went a half mile out off the leading edge of the active Australian Plate and were in 6,000 meters of water,” said Thomas, Ph.D., a researcher at Nova Southeastern University’s National Coral Reef Institute in Hollywood, Fla. “It was once believed there were no reefs on the north coast of Papua New Guinea since there were no shallow bays and lagoons typical of most coral reef environments. But there was lots of biodiversity to be found.”

Thomas and his team discovered new marine species including sea slugs (nudibranchs), feather stars (crinoids) and amphipods (genus Leucothoe). There was more variety of these indicator species found than there is in the entire length of Australia’s 1,600-mile Great Barrier Reef.

“This was an astonishing discovery,” Thomas said. “We returned to our labs and began to formally assess our collections.  We had no idea this lagoon’s bounty was so profound.”

The international team Thomas led included researchers from and the Scripps Institute of Oceanography in San Diego, the California Academy of Sciences and the National Botanical Gardens of Ireland. Their 3-week expedition ended late last year. While in Madang, they joined a large French contingent of scientists from the Paris Museum of Natural History.

The NSU-led research team’s findings will be shared with the local villagers, as well as regional and federal governments. It will also be published in peer-reviewed journals.

The Madang Lagoon faces many environmental threats by land-based pollution from a recently opened tuna cannery whose outfall is very close to the lagoon’s reefs. “Hopefully, our discoveries will strongly encourage governing bodies to recognize the environmental importance of the lagoon and work to stop the pollution,” Thomas said.

Source: National Science Foundation

The edge of the Greenland ice sheet, near Kangerlussuaq, is shown. Credit: Peter West, NSF

A new study that provides surprising details on changes in Earth’s climate from more than 100,000 years ago indicates that the last interglacial–the period between “ice ages”–was warmer than previously thought and may be a good analog for future climate, as greenhouse gases increase in the atmosphere and global temperatures rise.

The research findings also indicate that melting of the massive West Antarctic ice sheet may have contributed more to sea-level rise at that time than melting of the Greenland ice sheet.

The new results from the North Greenland Eemian Ice Drilling (NEEM) project were published in the Jan. 24 edition of Nature.

Logging of the ice core took place at the Ice2Sea drill site, 5 km out of the NEEM camp. Photo: NEEM ice core drilling project, http://www.neem.ku.dk

Members of the research team noted that they were working in Greenland during the summer of 2012 during a rare modern melt event similar to those discussed in the paper.

“We were quite shocked by the warm surface temperatures observed at the NEEM ice camp in July 2012,” said Dorthe Dahl-Jensen, of the University of Copenhagen, the NEEM project leader.

“It was simply raining, and, just as during the Eemian period, meltwater formed subsurface ice layers. While this was an extreme event, the present warming over Greenland makes surface melt more likely, and the predicted warming over Greenland in the next 50-100 years will potentially have Eemian-like climate conditions.”

The Eemian interglacial period began about 130,000 years ago and ended about 115,000 years ago.

The project logistics for NEEM are managed by Denmark’s Centre for Ice and Climate. The Arctic Sciences Section in the National Science Foundation’s Division of Polar Programs manages the U.S. support for the project.

In addition to Denmark and the United States, researchers from Belgium, Canada, China, France, Germany, Iceland, Japan, the Netherlands, South Korea, Sweden, Switzerland and the United Kingdom are also partners in NEEM.

The research published shows that during the Eemian interglacial, the climate in North Greenland was about 8 degrees Celsius warmer than at present. Despite this strong warming signal during the Eemian–a period when the seas were roughly four to eight meters higher than they are today–the surface in the vicinity of NEEM was only a few hundred meters lower than its present level, which indicates that the Greenland ice sheet may have contributed less than half of the total sea rise at the time.

“The new findings reveal higher temperatures in Northern Greenland during the Eemian than paleo-climate models have estimated,” said Dahl-Jensen.

The Research

The researchers looked at surface elevation and ice thickness in the early and later parts of the Eemian. Following the previous glacial period, 128,000 years before present, the surface elevation in the vicinity of NEEM was 200 meters higher than the present and the ice thickness decreased at a very high rate of 6 centimeters per year. Some 122,000 years before the present, the surface elevation was 130 meters below the present. In the late Eemian, 122,000 to 115,000 before present, the surface elevation remained stable at a level of 130 meters below the present with an ice thickness of 2,400 meters.

The research team estimated the Greenland ice sheet’s volume reduced by no more than 25 percent over 6,000 years. The rate of elevation change in the early part of the Eemian was high and the loss of mass from the Greenland ice sheet was likely on the the same order as changes observed during the last ten years.

2 km west of NEEM a 12 m long 3-inch core was drilled with the hand auger. Photo: Olivia Maselli NEEM ice core drilling project, http://www.neem.ku.dk

“The good news from this study is that Greenland is not as sensitive as we thought to temperature increases in terms of disgorging ice into the ocean during interglacial periods,” said Dahl-Jensen. “The bad news is that if Greenland did not disappear during the Eemian, Antarctica, including the more dynamically unstable West Antarctica, must be responsible for a significant part of the 4-8 meters of sea-level rise.”

Jim White, director of the Institute of Arctic and Alpine Research at the University of Colorado, Boulder, and the lead U.S. investigator on the NEEM project, said that while three previous ice cores drilled in Greenland in the last 20 years recovered ice from the Eemian, the deepest layers were compressed and folded, making the data difficult to interpret.

With this study, although there was some folding of the lowest ice layers in the NEEM core, sophisticated ice-penetrating radar helped scientists sort out and interpret the individual layers to paint an accurate picture of the warming of Earth’s Northern Hemisphere as it emerged from the previous ice age.

“When we calculated how much ice melt from Greenland was contributing to global sea rise in the Eemian, we knew a large part of the sea rise back then must have come from Antarctica,” said White. “A lot of us had been leaning in that direction for some time, but we now have evidence that confirms that the West Antarctic ice sheet was a dynamic and crucial player in global sea rise during the last interglacial period.”

The intense surface melt in the vicinity of NEEM during the warm Eemian period was seen in the ice core as layers of re-frozen meltwater. Meltwater from surface snow had penetrated the underlying snow, where it re-froze. Such melt events during the past 5,000 years are very rare by comparison, confirming that the surface temperatures at the NEEM site during the Eemian were significantly warmer than today, said the researchers.

The Greenland ice core layers–formed over millennia by compressed snow–are being studied in detail using a big suite of measurements, including stable water isotope analysis that reveals information about temperature and moisture changes back in time. Lasers are used to measure the water stable isotopes and atmospheric gas bubbles trapped in the ice cores to better understand past variations in climate on a year-by-year basis–similar in some ways to a tree-ring record.

“It’s a great achievement for science to gather and combine so many measured ice core records to reconstruct the climate history of the past Eemian,” said Dahl-Jensen. “It shows what a great team of researchers we have assembled and how valuable these findings are.”

A mound of crown-of-thorns starfish engulf the coral. Photo Christopher Bartlett

Most divers have seen the occasional brightly colored, many-limbed, spiny rubbery-looking Crown-of-Thorns starfish. They appear quite quirky and can be a good subject for macro photography. However, as predators, they also team up to form an extremely efficient coral killing machine.

The crown-of-thorns starfish, or sea star (Acanthaster planci) have, as most organisms on a reef, their place in the food chain and fulfill a role in a balanced and healthy reef system; they are however, voracious predators. I dive from Pemba Island, Zanzibar regularly and towards the end of a visit in late September 2009, I was told that one of the dive sites, home to leaf coral, lattice coral, and a soft-looking porite knuckle coral was under attack from a plague of crown-of-thorns starfish.

Crown-of-Thorns Starfish Facts

Young crown-of-thorns starfish feed on algae encrusted on the coral, common amongst rocks and rubble on the reef. At approximately six months of age, they start to eat coral and growth rates increase from 1 cm (0.39 in) to 25 cm (9.94 in) in the subsequent two-year period. Crown-of-thorns starfish spend about half their time feeding. When there are few crown-of-thorns starfish, they are elusive and hide in the reef and under corals during the day. Larger starfish (more than 40 cm (15.74 in)) usually feed during the day while smaller starfish (less than 20 cm (7.87 in)) usually feed at night. Extruding their stomachs onto the coral, they literally suck the life out of it.

Crown-of-thorns starfish feed mainly on faster growing table coral species, particularly from the genus Acropora, and may only eat a portion of the entire coral colony. As a result, the reef is able to recover quite rapidly from low levels of predation by crown-of-thorns starfish. Some reefs seem to support small populations of crown-of-thorns starfish for many years, with only a small reduction in coral cover. Scientists estimate that a healthy coral reef with about 40-50 percent coral cover can support 20-30 crown-of-thorns starfish per hectare (2.47 acres).

A mound of crown-of-thorns starfish. Photo Christopher Bartlett

However, a prevalence of crown-of-thorn starfish in large numbers can result in intense competition for food with most types of corals being eaten, including species such as slow-growing Porites spp., which are not usually eaten by the starfish. During a severe outbreak, the crown-of-thorns starfish can number 20 per square meter (10.76 sq ft) or more, piling on top of each other three or four deep at times. They are able to devour so much that they can kill most of the living coral in that part of the reef, reducing hard coral cover from the usual 25 – 40 percent of the reef surface to less than 1 percent. Such a reef can take over 10 years to recover.

What Causes Outbreaks of Crown-of-Thorns Starfish?

Scientists support three theories on the causes of outbreaks of the crown-of-thorns starfish. These theories have neither been proved nor disproved. Firstly, fluctuations in crown-of-thorns starfish populations are a natural phenomenon. Just like any other organism, populations vary. Secondly, human exploitation of the coastal zone has increased the flow of nutrients to the sea and has resulted in an increase in planktonic food for the larvae of crown-of-thorns starfish. The improved survival of larvae has led to an increase in the number of adult starfish which results in outbreaks.

Crown-of-thorns starfish spawn over four to five months a year when water temperatures are around 28°C (82° F). The starfish release eggs and sperm into the water through pores on the top of their central disc and when the eggs are fertilized, these develop into larvae that drift like plankton for two to four weeks. The one to two millimeter juveniles settle onto the reef and live among rocks and rubble on the reef, remaining almost invisible until they are about six months old. They first breed when two to three years old and continue to reproduce for five to seven years. Each female can spawn up to 60 million eggs during a single season. By gathering together to spawn to increase the chance of fertilization, fertilization rates for crown-of-thorns starfish are, in fact, the highest measured for any invertebrate. Thus, with even more favorable factors, their proliferation could be increased considerably.

The final theory is that the removal of the natural predators of the crown-of-thorns starfish has allowed populations to expand. Although these starfish have few predators, one theory suggests that predators play an important role in keeping starfish populations balanced. Predators of adult crown-of-thorns starfish include the giant triton snail (genus: Charonia), the napoleon or Maori wrasse (Cheilinus undulatus), the starry pufferfish (Arothron stellatus) and the titan triggerfish (Balistoides viridescens). The giant triton snail is highly prized and heavily collected for sale to landlubbers (and ignorant divers); the shells for sale in tourist shops on Unguja Island (Zanzibar) and in Dar-es-Salaam have come from somewhere. However, the triton snail can consume relatively few adult crown-of-thorns starfish per week and thus its capacity to prevent starfish outbreaks seems limited, although it plays an important role when the starfish numbers are stable.

Predation by other reef fish on juvenile starfish might also limit crown-of-thorns starfish populations. Juvenile starfish are most likely to be eaten aged around six months, when they start to feed on coral. If numbers of the predator fish were depleted by fishing activities, this might allow an abnormally large number of starfish to survive to maturity. There is no substantial evidence at this time to show that commercially exploited fish eat significant numbers of juvenile crown-of-thorns starfish.

The Dive Site

Crown-of-thorns leave a distinct trail of dead coral behind them. Photo Christopher Bartlett

There is little human habitation near the dive site in question, nor any rivers to bear new nutrients from further a-field. There is subsistence fishing in the area, including some illegal dynamite fishing, and fishermen do not seem at all bothered about the size or type of fish caught. Given that there is no data available on past fish populations, it is impossible to state that their numbers are in decline, but it would not be beyond the realms of possibility. The numbers of starfish larvae that usually survive and then settle is unknown and it is difficult to estimate feeding rates of predators required to keep them in check.

Whilst the causes are therefore impossible to define categorically, the existence of abnormal numbers of crown-of-thorns starfish is easy. On returning in early December, armed with what I hoped to be a solution to the problem, I dropped onto the site to gauge the progress of the preceding two months. Sections of the dive site, roughly 10 m (32 ft) wide and 20 to 30 m (65 ft – 98 ft) long, had been destroyed by the slowly creeping underwater zombie-like horde, leaving tracts of coral completely white and, critically, dead. The crown-of-thorns starfish appeared in patches, seemingly moving from the shallower sections of the reef (10m) to the edge of the wall (17m), advancing in an underwater phalanx, in parts stacked four high.

Dealing With the Outbreak

In the past, crown-of-thorns starfish would be physically removed from the reef and buried on land. This method has several drawbacks though. Firstly, the starfish cling on to the reef and yanking them off damages the reef. Secondly, they are covered in sharp, toxic spines (the toxins come from the coral that they eat) that deliver very painful and sometimes dangerous stings, which necessitates them being handled with tongs or sharp sticks. This makes removal slow and labor-intensive. Another method tested in the past was cutting them up under water, but this too damages the coral, there is still a considerable risk of being stung and crown-of-thorns starfish that have been cut in four were observed still alive two weeks later!

Research on the Great Barrier Reef in Australia provided the solution that I was going employ. An injection of sodium bisulphate solution into the center of the crown-of-thorns starfish has been found to kill them in a couple of days, and has no effect on other marine organisms. Thus armed with this knowledge, I purchased some 60ml syringes, some long needles through eBay and ordered the cheap and readily available chemicals from a pool cleaning company, then crossed my fingers that I would not be required to do some explaining at Dar-es-Salaam airport.

Liquefaction occurring between 24 and 36 hours after injection of sodium bisulfite. Photo Christopher Bartlett

Once in Pemba and over the dive site, we mixed 200 grams of sodium bisulphate with 720 ml of seawater and filled six syringes. Accompanied by two other divers, I dropped down. Each starfish was to be injected with 2 ml, and thus one syringe would deal with 30 starfish. Working mainly head down and feet up, it took about 15 to 20 minutes to empty our syringes. The skin of the crown-of-thorns starfish is quite thick, but it has a sort of anal-like aperture at the center of its topside and the needles slipped in easily. One diver collected the syringes, surfaced, refilled and came down again. In total, 12 syringe-loads were emptied in less than an hour, totaling around 360 injections. Of course, some recipients may have received a bit more than 2 ml to begin with and no doubt, some specimens were done twice in the disorientating process!

Over the next week, we returned twice to tend to neighboring patches and the initial site was checked. The results were nothing short of spectacular – after a day, the crown-of-thorns starfish were starting to become flaccid and their skins were not as tough (and thus injected specimens were easily identified) and a couple (that probably received an extra dose) were splitting down the middle, but still moving. After two to three days, the specimens were dead and in various states of liquefaction. It resembled a sci-fi scene; a patch of gooey white substance with the spines sprinkled on top.

On returning in November 2010, the starfish were no longer evident, other than the odd one here or there, though the track of their passage across the reef clearly was. Paths of coral rubble ran down the top of the reef to the edge of the wall, as if cut by an underwater lawnmower. Fortunately, the dive site is part of a long stretch of wall and the affected area only covers three small sections and the rest is unharmed.

It was a very effective way, in terms of both time and cost, of restoring balance to the reef.

If you could build a city for one million people from scratch, which infrastructure should you put on the drawing board first? This question, as far as Monash Water for Livability CEO Rob Skinner is concerned, has only one answer – the plumbing.

Water-sensitive urban design is slowly seeping into our cities. The City of Mandurah in Western Australia, for example, has adopted a stormwater management plan focused on retrofitting traditional stormwater systems, stormwater harvesting and water retention through integrating design and infrastructure. Credit: City of Mandurah

“Cities are built around transport and employment needs. Only afterwards comes the question: how do we plumb in the water system?” says Professor Skinner, who plays a pivotal role in the International Water Association’s (IWA) Cities of the Future program.

Prof. Skinner warns that if we don’t change this approach, our expanding cities will be at serious risk of locking in a pattern of design and development that means more expensive water supply and increased environmental damage.

Experts predict that the world’s cities combined will gain almost one million extra people a week leading up to 2050. Already, 68 percent of Australia’s population live in cities; by 2050, this figure is expected to reach 80 percent.

In some of the world’s cities, pipelines are losing 50 percent of their water through leaks. In developing countries, poor water infrastructure is compounding already-dire sanitation issues.

Population and water supply issues are even more critical for Asian cities. Asia currently has 13 “megacities” – cities with at least 10 million people. By 2025, it will have gained another nine.

Steve Moddemeyer – head of the sustainable development practice for Seattle-based architecture and planning firm Collins Woerman, and a leader of the IWA’s Cities of the Future program – says population growth and outdated infrastructure models are on a collision course.

“We are building cities at breakneck pace, particularly in the developing world. The problem is that we’re building the wrong kind of water infrastructure for the 21st century. We’re using models from the 19th and 20th centuries,” he says.

The challenge to supply enough safe water to our growing cities is invoking a quiet revolution among water professionals and engineers across the globe – a revolution in which water management, treatment and delivery practices are being overhauled.

“The Cities of the Future program is about recognizing the issues that cities are facing, and looking for the new models that are doing a better job at building resilience,” explains Mr Moddemeyer.

Building resilience means managing water flow so that a city can withstand both extremely dry and wet times. But, it is far more complex than just laying new pipes or constructing dams.

Delegates at 2010′s IWA World Water Congress in Montreal agreed on a vision for future city water planning. They drew up 12 planning principles that position water as central to a city’s ability to develop sustainably.

At this year’s IWA Congress in Korea, delegates identified 10 challenges that cities will need to deal with to realize these 12 principles.

“The most critical challenges for existing cities are the institutional arrangements, regulations and underlying culture of water management agencies,” says Prof. Skinner.

The revolution in the water sector considers water differently than in the past, when all water needed to be of a set quality standard. Industry experts are now talking about water being “fit for purpose”. This means that high-quality water is provided for drinking, but stormwater and recycled water of a lower quality are increasingly used to water parks and gardens.

Seeing water as fit for purpose means that not all water needs to go through the stringent and energy-guzzling filtration processes needed to produce drinking water.

Instead, it makes better use of the various water resources already found in cities and saves on energy and other inputs.

Melbourne Drought a Wake-Up Call

In 2008, Melbourne Water launched an ambitious program to establish 10,000 new rain gardens. Rain gardens capture stormwater runoff from impervious surfaces, and slow the rate and volume of water flushing through drains into rivers and creeks. They also promote healthier waterways by filtering pollution and add to the attraction and liveability of the city. Credit: Associate Professor Peter Breen

With almost 4.5 million people, Melbourne is Australia’s second-largest city. It is a global pioneer of the urban water revolution, having been one of the first cities to recognize the IWA’s 12 principles.

The city has access to what many consider “dream” water catchments that afford a relatively cheap and high-quality water supply. However, the drought of the past decade, which almost emptied Melbourne’s reservoirs, has woken many residents to the importance of water.

“During the drought, parks and trees were dying. Only a quarter of our football or cricket fields could be watered, meaning three-quarters of our sports facilities were unsafe to play on,” says Prof. Skinner. “Suddenly, there was a wake-up call that livability in Melbourne meant healthy waterways and green spaces.”

The city’s response was to build Australia’s largest desalination plant to treat seawater and brackish water, and pipe drinkable water 84 kilometers to the city.

“It will stand Melbourne in good stead, but we don’t want to be in a situation again where we have to build another desalination plant,” Prof. Skinner states. “Desalination provides water security and reduces the otherwise singular reliance on dams for water supply, but it is an option that primarily focuses on the single need of water supply.”

For the past three years, Victorian government bodies and water utilities have shifted their focus from traditional centralized water supply and wastewater disposal. The state’s water industry is now gearing itself up for a system that values all water as fit for purpose, and integrates it from various sources, such as rainwater, stormwater runoff and recycled sewage.

In 2011, a Victorian ministerial advisory council noted that while Melbourne reused 31 billion liters of treated wastewater and stormwater in 2010 – representing 7.5 percent of the total water demand – significant scope remains to increase the use of fit-for-purpose resources.

With the city’s population projected to reach 6.4 million by mid-century, annual demand for drinking water will increase by about 150 percent. But over the past 15 years, average inflows into the city’s main reservoirs have been one-third less than the previous 80 years.

“There is now a sense of urgency to reform the way water is valued, planned for and managed in Melbourne,” says Prof. Skinner.

Decentralizing Supply

Paul Reiter, Executive Director of the IWA, says water planners will need to decentralize water supply systems to build resilience.

“Water systems can be built into a 2,000-unit housing network,” he says. “In Europe, this might be 10,000 – it may be more in other cities. But, building bigger systems of centralized services will lead to infrastructure capacity failures.”

Other cities around the world pioneering the water revolution have embraced smaller-scale urban planning solutions.

In Hamburg, a former military base has been converted into an urban space for 630 homes. The water utility supplier, Hamburg Wasser, saw an opportunity to link three traditionally separate utilities. The homes are heated from waste that is converted to fuel; the separation of stormwater in the drainage infrastructure is used to irrigate the green open spaces.

The Jenfelder Au in Hamburg integrates water, wastewater and energy supplies. Credit: Hamburg Wasser

Dense parts of Philadelphia have been retrofitted with stormwater capture systems, such as rain gardens, to help alleviate contaminated water entering the city’s natural waterways. And, Copenhagen has improved the ecological health of its harbor and the city’s livability by reducing wastewater discharge from sewers and industrial companies.

“Every area is different in terms of climate, geography, population density and closeness to existing central services,” explains Prof. Skinner.

“So, when you decide to redevelop or develop, you have to consider what the fit-for-purpose options are for each area. There may well be a more efficient way of serving those semi-centralized areas. Sometimes it is stormwater capture, sometimes it is recycled water, and sometimes it is the centrally supplied service.”

The following is part one in a series on the National Science Foundation’s Science, Engineering and Education for Sustainability (SEES) investment.  Visit parts one, two,three,four, five, six, seven, eight and nine in this series.

Marcellus Shale natural gas drilling is proceeding apace in Pennsylvania. Credit: Chuck Anderson, Penn State

Amity, Pennsylvania. Epicenter of the natural gas-containing geological formation known as the Marcellus Shale.

Amity lies in Washington County near Anawanna, Pa. Once, Native Americans lived there. They named it Anawanna, or “the path of the water,” in recognition of its many rivers and streams. Today the Native American Anawanna is but a whisper in tales of the past, but the path of the water for which it’s named is making headlines.

The Marcellus Shale Formation underlies some 95,000 square miles of land, from upstate New York in the north to Virginia in the south, to Ohio in the west. The bull’s-eye, however, is under Pennsylvania in places like Amity. There the gas-bearing thickness of the shale reaches 350 feet; it thins to less than 50 feet in other areas.

The Marcellus Shale gas reservoir may contain nearly 500 trillion cubic feet of technically-recoverable gas. At current use rates, that volume could meet the U.S. demand for natural gas for more than 20 years. The shale’s proximity to the heavily populated mid-Atlantic and Northeast makes its development economically advantageous. Already, more than 4,000 shale gas wells have been drilled in Pennsylvania.

But the Marcellus Shale has a bête noire. With such rapid development, gas exploitation is creating environmental challenges for Pennsylvania–and beyond.

Retrieving the Marcellus Shale’s gas requires a process known as hydraulic fracturing, hydrofracking or simply fracking.

Geoscientist Susan Brantley of Penn State doing field work in the Marcellus Shale region. Credit: Penn State

Fracking involves the use of large quantities of water, three to eight million gallons per well, mixed with additives, to break down the rocks and free up the gas. Some 10 to as much as 40 percent of this fluid returns to the surface as “flowback water” as the gas flows into a wellhead.

Once a well is in production and connected to a pipeline, it generates what’s known as produced water. “Flowback and produced water,” says Susan Brantley, a geoscientist at Penn State University, “contain fluid that was injected from surface reservoirs–and ‘formation water’ that was in the shale before drilling.”

Enter the Bête Noire.

Marcellus Shale underlies a U.S. East Coast region from New York to Virginia. Credit: USGS

These flowback fluids carry high concentrations of salts, and of metals, radionuclides and methane. “Such chemicals,” says Brantley, “can affect surface and groundwater quality if released to the environment without adequate treatment.”

The rapid pace of Marcellus Shale drilling has outstripped Pennsylvania’s ability to document pre-drilling water quality, even with some 580 organizations focused on monitoring the state’s watersheds. More than 300 are community-based groups that take part in volunteer stream monitoring.

Pennsylvania has more miles of stream per unit land area than any other state in the United States. “It’s overwhelming to keep track of,” says Brantley. “These community organizations have identified a need for scientific and technical assistance to carry out accurate stream assessments.”

Many of Pennsylvania's streams are unpolluted havens for aquatic life, including trout. Credit: State of Pennsylvania

Working through the National Science Foundation’s (NSF) Susquehanna Shale Hills Critical Zone Observatory (CZO), one of six such observatories in the continental U.S. and Puerto Rico, Brantley studies the “critical zone” where water, atmosphere, ecosystems and soils interact.

Now, with a grant from NSF’s Science, Engineering and Education for Sustainability (SEES) Research Coordination Networks (RCN) activity, Brantley is developing a Marcellus Shale Research Network.

Identifying Citizen Scientist Groups

The network will identify groups in Pennsylvania that are collecting water data in the Marcellus Shale region; create links among these organizations to meld the resulting data; and organize a water database through the NSF-funded Consortium of Universities for the Advancement of Hydrologic Sciences.

The database will be used to establish background concentrations of chemicals in streams and rivers, and ultimately to assess changes throughout the Marcellus Shale area.

The results, Brantley hopes, will help community groups evaluate hydrogeochemical data. The network will use geographic information systems that incorporate population and economic data to evaluate the potential for public health risks.

“An outcome of the NSF investment in the Susquehanna Shale Hills Critical Zone Observatory has been a better interpretation of the chemistry and flow of groundwater in shale,” says Enriqueta Barrera, program director in NSF’s Division of Earth Sciences, which funds the CZOs.

Hundreds of streams and rivers large and small flow through the Marcellus Shale Formation. Credit: NPS

“The SEES-RCN project will use this information in assembling data collected by watershed associations, government agencies, and water scientists to further knowledge on the effect of hydrofracking on groundwater properties.”

The Marcellus Shale RCN, says Brantley, “is designed to act as an ‘honest broker’ that collates datasets and teaches ways of synthesizing the data into useful knowledge. The approach stresses that volunteer data acts as a ‘canary in a coal mine’ to inform agencies about when and where they need to intensify water quality monitoring.”

Of particular concern are concentrations of salts such as barium and strontium, high in some discharges as a result of the mixing of gas drilling fluids with naturally-occurring barium-strontium-containing waters.

“Barium can cause gastrointestinal problems and muscular weakness,” says Brantley, “when people are exposed to it at levels above the EPA drinking water standards, even for relatively short periods of time.

“Animals [such as cows, pigs, sheep] that drink barium-laced waters over longer periods sustain damage to kidneys and have decreases in body weight, and may die of the effects.”

The waterways of Pennsylvania have recorded many of the important human activities in the history of the United States, Brantley says. “It’s expected that they will record the development of the Marcellus Shale gas as well.”

The rise and fall of coal mining is found in concentrations of dissolved sulfates in the state’s rivers. Pennsylvania’s air, water and soils retain the signature of the steel industry and of coal-burning over the last century in their low-level manganese contamination.

Extensive Sampling Required

Documenting the effects of shale gas extraction, says Brantley, requires extensive water sampling and a database of long-term records.

A temporary freshwater impoundment to be used for fracking, or hydraulic fracturing. Credit: Chuck Anderson, Penn State

In the past, monitoring sometimes has not begun until after effects were noticed.  But times are changing. “In the future,” says Brantley, “many monitoring networks of all kinds will need to include citizen scientists to keep costs down, and research scientists will need to learn to use such networks to the best outcome.”

Can we have natural gas development and clean waterways?

The Marcellus Shale Research Network will provide much-needed answers, says Barrera. “Successfully developing new energy resources while maintaining healthy ecosystems,” she says, “is the very heart of sustainability.”

Source: National Science Foundation

With population growth, urbanisation and economic development, the demand for freshwater in urban areas are increasing throughout Europe. At the same time, climate change and pollution are also affecting the availability of water for city residents. How can Europe’s cities continue providing clean freshwater to their residents?

Copenhagen July 2, 2011 - Photo by Lisa Risager

In July 2011 intense rains left parts of Copenhagen flooded. The urban drainage systems could not handle the amount of water that came down in intensities up to 135 mm in two hours. Copenhagen’s water problems did not end there. Shortly after the floods, large parts of the city were affected for weeks by contaminants in the drinking water in connection with water main repairs. Similar types of water-related problems occur in other cities.

More than three quarters of European citizens live in urban areas and rely on clean water in cities. Approximately one fifth of the total freshwater abstracted in Europe supplies public water systems – water that is directed to households, small businesses, hotels, offices, hospitals, schools and some industries.

Ensuring a steady supply of clean water to the public is not a simple task. The water system needs to consider many factors including population and household size, changes in the physical characteristics of land surfaces, consumer behaviour, economic sector demands (such as tourist activities), the water’s chemical composition and the logistics of water storage and transport. It also has to factor in the challenges from climate change that can include unexpected flooding, heat waves and periods of water scarcity.

To prevent urban water crises, we need to manage water resources effectively at every stage: from the supply of clean water to its different uses by the consumers. This could involve reducing consumption as well as finding new ways of collecting and using water. Water management should also be better integrated within wider urban management while taking into account characteristics of the local environment.

Paying for the Water We Use

Advances in technology and new pricing systems alone have already been proven to significantly reduce the amount of water used by households, which is typically 60-80 % of the public water supply across Europe. Technological improvements to domestic appliances such as washing machines and dishwashers, for example, have helped reduce water use without requiring a change in behaviour or an awareness of water issues.

More significant improvements are also possible with changes to the use of water for personal hygiene, which currently accounts for 60% of water use in households. Cistern replacement devices in toilets, for example, provide a cheap and simple way to reduce the water used by one litre per flush. Minor adjustments to shower systems, such as by aerating the water flow, can also result in water savings.

As set out in the EU Water Framework Directive, linking the price of water to the volume of water consumed can provide an incentive for a more sustainable use of water. In England and Wales, people living in metered properties use on average 13 % less water than those in unmetered homes.

Re-using Rain and Greywater

Only 20 % of water used by the sectors receiving a public water supply is actually consumed. The other 80 % is returned to the environment, primarily as treated wastewater. Concreted and sealed surfaces in cities typically direct the rainfall to the sewer networks where it is merged with wastewater. This prevents the rainfall from infiltrating the soil and forming part of our groundwater storage that can benefit us at a later date. Rain runoff and wastewater often pass through water treatment plants before being returned to rivers, usually far away from the cities. With some changes to urban water systems, both rain water and less polluted wastewater could be returned to the city’s water users.

One of these changes is the reuse of greywater. Greywater refers to all household wastewater that is not from toilets, such as wastewater from baths, showers, washbasins and the kitchen. This water can be treated directly on site or left untreated for use with less than drinking water quality for e.g. flushing toilets.

Cities could also harvest rainwater by collecting rainwater flowing from a roof or driveway in a receiving container and this water could be used for non-potable activities such as toilet flushing, washing cars or gardening. It could also be led directly to a ground water recharge. Such systems can be installed in households or businesses and will not require changes in consumption habits from the water users. There are, however, more steps that can be taken to improve the supply of water before it reaches domestic premises.

Keeping the water in the city by allowing the water to infiltrate the soil and accumulate in water bodies provides many benefits, including offering recreational space to local residents and creating a cooling effect during heat waves.

Reducing Loss

The loss of water through leakages can be considerable; in Croatia nearly 40 % of the total water supply is lost in the water transportation network. Leakages can be prevented through maintenance and water network renewal, and also through the use of new technologies. Such technologies may involve sensors that recognise and locate the noise from a leak or devices that use radio signals to detect the presence of flowing water. With the application of these technologies, public water systems no longer need to face the extra burden of water loss through leakages when fulfilling water demands with limited supplies. Renewing the water networks, however, could require significant infrastructure investments.

Time for Action

Achieving a more sustainable use of urban public water supplies requires not only the implementation of measures such as those outlined above, but also raising public awareness on water conservation issues.

Various means are available to inform domestic, business and tourist water consumers, including websites, school education programmes, local authority leaflets and mass media. The eco-labelling of appliances and eco-certification of hotels, for example, can also play an important role in raising awareness by helping consumers make informed choices about water efficiency and conservation.

A truly sustainable use of our fresh water resources cannot be achieved without additional improvements to the sustainability of urban water use.

Related Publications

Towards efficient use of water resources in Europe

Urban adaptation to climate change in Europe

Crown of Thorns starfish. Photo Jon Hanson/Wikimedia Creative Commons

Can we save the reef by controlling crown of thorns starfish?

The Great Barrier Reef has lost half its coral cover in the last 27 years. The loss was due to storm damage (48 percent), crown of thorns starfish (42 percent), and bleaching (10 percent) according to a new study published in the Proceedings of the National Academy of Sciences recently by researchers from the Australian Institute of Marine Science (AIMS) in Townsville and the University of Wollongong.

“We can’t stop the storms but, perhaps we can stop the starfish. If we can, then the Reef will have more opportunity to adapt to the challenges of rising sea temperatures and ocean acidification,” says John Gunn, CEO of AIMS.

“This finding is based on the most comprehensive reef monitoring program in the world. The program started broadscale surveillance of more than 100 reefs in 1985 and from 1993 it has incorporated more detailed annual surveys of 47 reefs,” says one of the program’s original creators, Dr Peter Doherty, Research Fellow at AIMS.

“Our researchers have spent more than 2,700 days at sea and we’ve invested in the order of $50 million in this monitoring program,” he says.

“The study shows the Reef has lost more than half its coral cover in 27 years. If the trend continued coral cover could halve again by 2022. Interestingly, the pattern of decline varies among regions. In the northern Great Barrier Reef coral cover has remained relatively stable, whereas in the southern regions we see the most dramatic loss of coral, particularly over the last decade when storms have devastated many reefs. ” says Peter Doherty.

Three Clear Factors

The study clearly shows that three factors are overwhelmingly responsible for this loss of coral cover. Intense tropical cyclones have caused massive damage, primarily to reefs in the central and southern parts of the Reef, while population explosions of the coral-consuming Crown-of-thorns starfish have affected coral populations along the length of the Reef. Two severe coral bleaching events have also had major detrimental impacts in northern and central parts of the GBR.

“Our data show that the reefs can regain their coral cover after such disturbances, but recovery takes 10-20 years. At present, the intervals between the disturbances are generally too short for full recovery and that’s causing the long-term losses,” says Dr Hugh Sweatman, one of the study’s authors.

“We can’t stop the storms, and ocean warming (the primary cause of coral bleaching) is one of the critical impacts of the global climate change,” says AIMS CEO, John Gunn. “However, we can act to reduce the impact of crown of thorns,” he says. “The study shows that in the absence of crown of thorns, coral cover would increase at 0.89 percent per year, so even with losses due to cyclones and bleaching there should be slow recovery.

“We at AIMS will be redoubling our efforts to understand the life cycle of crown of thorns so we can better predict and reduce the periodic population explosions of crown of thorns. It’s already clear that one important factor is water quality, and we plan to explore options for more direct intervention on this native pest.”

The analysis presented in the paper was conducted with partial support from the Australian Government’s National Environmental Research Program.

Source: Australian Institute of Marine Science