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Grand Canyon

Artificial floods: Restoring the ecological integrity of rivers

Artificial floods: Restoring the ecological integrity of rivers

“You can never step into the same river,
for new waters are always flowing on to you.”
—Heraclitus of Ephesus

Rushing rivers, with their unremitting twists and turns and continuous renewal, are often used as a metaphor for life, but the analogy is just as appropriate for scientific research, I reflected as I walked along the banks of a sparkling, turquoise-blue river in the heart of the Swiss National Park. The never-ending cycle of formulating, testing, and modifying evidence-based hypotheses is a hallmark of how humanity acquires new knowledge.

Conducting experiments with rivers is especially challenging because they can never be isolated from their social and ecological contexts. Worldwide, people have appropriated more than half the globe’s accessible surface water by erecting hundreds of thousands of dams. Although these dams provide many societal advantages, including hydropower, water storage, and flood control, they also severely disrupt the ecosystems within which they’re placed. Recently, however, there has been a growing focus on using intentional water releases from the very dams that disturb rivers as ecological restoration tools.

The Spöl River flows through the heart of the beautiful Swiss National Park. (Credit: Terri Cook)

Thanks to the support of an EGU Science Journalism Fellowship, I was hiking next to the Spöl River, a beautiful ribbon of crystal-clear water winding through a deep gorge carved into a soaring limestone upland in the Rhaetian Alps, which are tucked into the country’s southeastern corner. The craggy peaks and towering spruce, pine, and golden larch trees provided a startling contrast to the arid, high-desert scenery along the Colorado River in the Grand Canyon where, several years earlier, I had witnessed the Colorado River’s rapid rise following a so-called “artificial flood” unleashed from Glen Canyon Dam.

Multiple manmade floods have been conducted in the Grand Canyon to benefit the corridor’s physical, cultural, and biological resources, most notably endangered native fish and the disappearing sandbars upon which many organisms, as well as the multimillion-dollar rafting industry, depend. Following years of intensive scientific study and negotiations between the numerous stakeholders, the U.S. government recently implemented a long-term strategy for releasing manmade floods following large sand inputs from tributaries that join the main stem below Glen Canyon Dam. The reason for this timing is to move the recently introduced sand up onto the banks to replenish the shrinking sandbars.

Although these events have been widely reported in the press, few people realize that one of the most important models for designing the Grand Canyon experiments was the Spöl River. I had thus traveled to Switzerland to report on the globe’s best example of how, using carefully designed and monitored floods, scientists and managers have collaborated for a decade and a half to restore—and sustain—this river’s ecological integrity.

Of Fish and Floods

From the Livigno Reservoir on the Italian-Swiss border, the Spöl flows through Switzerland’s only national park before joining the Inn River, a tributary of the Danube, 28 kilometers downstream. Inside the park, the Spöl is sandwiched between two dams, the 130-meter-high Punt dal Gall on the Italian border and the 73-meter-high Ova Spin downstream. Built in the 1960s following a contentious vote, the dams are towering concrete barriers that seemed to me to be out of proportion to the river’s modest size.

Punt dal Gall Dam: The 130-meter-high Punt dal Gall Dam was built in the 1960s on the Swiss-Italian border. (Credit: Terri Cook)

Studies in the national park in the late 1980s confirmed that two decades of reduced flows had severely altered the stream, Ruedi Haller, the park’s Research and Geoinformation Manager, told me as we hiked. The riverbed had become choked with fine-grained sediments, reducing brown trout spawning grounds and changing its assemblage of fauna.

In 1990, a mandated flushing of the safety release gates at the base of the upper Punt dal Gall Dam noticeably improved the ecological conditions downstream, flushing out many of the fine-grained sediments and decreasing the accumulations of mosses, algae, and bottom-dwelling fauna that had taken advantage of the low and steady dam-controlled flows. Within months, however, the Spöl returned to its prior condition. As Chris Robinson of the Swiss Federal Institute of Aquatic Science and Technology explained to me, this first experiment indicated that a single artificial flood could not sustain the river’s ecological integrity over the long term.

Following this initial success, park authorities, researchers, and representatives of the Engadin Hydropower Company, which operates the dams, gradually overcame their former distrust and began to work together to design and implement a flood release program to improve the river’s long-term health. Since then, operators have unleashed more than 25 experimental floods that, by mimicking the seasonally variable conditions to which native fauna and flora have adapted, have recreated an ecosystem much more typical of an Alpine stream. The current flood release program incorporates two artificial floods per year, with the magnitudes determined by annual monitoring.

The Sarine

I also visited a second managed river, the Sarine, near Bern, to watch scientists assess the results of an artificial flood that had just been completed. Among the team working at the site was Michael Doering of the Zurich University of Applied Sciences. He was using a drone to snap post-flood photographs to compare with images taken just before the event to provide a bird’s-eye view of the changes the water had wrought.

Michael Doering uses images taken by a drone to determine the amount of sediment relocated during an artificial flood. (Credit: Terri Cook)

Once analyzed, these and other data will show whether the Sarine flood was large enough to achieve the goals of moving sediment from the banks into the stream and raising the water level high enough to benefit the aquatic and terrestrial ecosystems straddling its banks. Both are necessary, explained Doering, to support a healthy amount of biodiversity, which dammed rivers typically lack.

Through a revision to its Water Protection Act, Switzerland has committed to eliminating the negative impacts of hydropower plants on all of the country’s rivers. Of the more than 700 facilities that need to be mitigated by 2030, it is envisaged that up to about 40 will use artificial floods, according to Martin Pfaundler of the Swiss Federal Office for the Environment. To accomplish this, scientists and water managers will rely on the experience obtained not only from Swiss rivers, but also—as part of the ever-flowing research cycle—from the new knowledge gained from the Colorado.

By Terri Cook, a science and travel writer and winner of the EGU’s 2016 Science Journalism Fellowship.

The best of Imaggeo in 2015: in pictures

The best of Imaggeo in 2015: in pictures

Last year we prepared a round-up blog post of our favourite Imaggeo pictures, including header images from across our social media channels and Immageo on Mondays blog posts of 2014. This year, we want YOU to pick the best Imaggeo pictures of 2015, so we compiled an album on our Facebook page, which you can still see here, and asked you to cast your votes and pick your top images of 2015.

From the causes of colourful hydrovolcanism, to the stunning sedimentary layers of the Grand Canyon, through to the icy worlds of Svaalbard and southern Argentina, images from Imaggeo, the EGU’s open access geosciences image repository, have given us some stunning views of the geoscience of Planet Earth and beyond. In this post, we highlight the best images of 2015 as voted by our Facebook followers.

Of course, these are only a few of the very special images we highlighted in 2015, but take a look at our image repository, Imaggeo, for many other spectacular geo-themed pictures, including the winning images of the 2015 Photo Contest. The competition will be running again this year, so if you’ve got a flare for photography or have managed to capture a unique field work moment, consider uploading your images to Imaggeo and entering the 2016 Photo Contest.

Different degrees of oxidation during hydrovolcanism, followed by varying erosion rates on Lanzarote produce brilliant colour contrasts in the partially eroded cinder cone at El Golfo. Algae in the lagoon add their own colour contrast, whilst volcanic bedding and different degrees of welding in the cliff create interesting patterns.

 Grand Canyon . Credit: Credit: Paulina Cwik (distributed via imaggeo.egu.eu)

Grand Canyon . Credit: Credit: Paulina Cwik (distributed via imaggeo.egu.eu)

The Grand Canyon is 446 km long, up to 29 km wide and attains a depth of over a mile 1,800 meters. Nearly two billion years of Earth’s geological history have been exposed as the Colorado River and its tributaries cut their channels through layer after layer of rock while the Colorado Plateau was uplifted. This image was submitted to imaggeo as part of the 2015 photo competition and theme of the EGU 2015 General Assembly, A Voyage Through Scales.

Water reflection in Svalbard. Credit: Fabien Darrouzet (distributed via imaggeo.egu.eu)

Water reflection in Svalbard. Credit: Fabien Darrouzet (distributed via imaggeo.egu.eu)

Svalbard is dominated by glaciers (60% of all the surface), which are important indicators of global warming and can reveal possible answers as to what the climate was like up to several hundred thousand years ago. The glaciers are studied and analysed by scientists in order to better observe and understand the consequences of the global warming on Earth.

Waved rocks of Antelope slot canyon - Page, Arizona by Frederik Tack (distributed via imaggeo.egu.eu).

Waved rocks of Antelope slot canyon – Page, Arizona by Frederik Tack (distributed via imaggeo.egu.eu).

Antelope slot canyon is located on Navajo land east of Page, Arizona. The Navajo name for Upper Antelope Canyon is Tsé bighánílíní, which means “the place where water runs through rocks.”
Antelope Canyon was formed by erosion of Navajo Sandstone, primarily due to flash flooding and secondarily due to other sub-aerial processes. Rainwater runs into the extensive basin above the slot canyon sections, picking up speed and sand as it rushes into the narrow passageways. Over time the passageways eroded away, making the corridors deeper and smoothing hard edges in such a way as to form characteristic ‘flowing’ shapes in the rock.

 Just passing Just passing. Credit: Camille Clerc (distributed via imaggeo.egu.eu)

Just passing. Credit: Camille Clerc (distributed via imaggeo.egu.eu)

An archeological site near Illulissat, Western Greenland On the back ground 10 000 years old frozen water floats aside precambrian gneisses.

Sarez lake, born from an earthquake. Credit: Alexander Osadchiev (distributed via imaggeo.egu.eu)

Sarez lake, born from an earthquake. Credit: Alexander Osadchiev (distributed via imaggeo.egu.eu)

Beautiful Sarez lake was born in 1911 in Pamir Mountains. A landslide dam blocked the river valley after an earthquake and a blue-water lake appeared at more than 3000 m over sea level. However this beauty is dangerous: local seismicity can destroy the unstable dam and the following flood will be catastrophic for thousands Tajik, Afghan, and Uzbek people living near Mugrab, Panj and Amu Darya rivers below the lake.

Badlands national park, South Dakota, USA. Credit: Iain Willis (distributed via imaggeo.egu.eu)

Badlands national park, South Dakota, USA. Credit: Iain Willis (distributed via imaggeo.egu.eu)

Layer upon layer of sand, clay and silt, cemented together over time to form the sedimentary units of the Badlands National Park in South Dakota, USA. The sediments, delivered by rivers and streams that criss-crossed the landscape, accumulated over a period of millions of years, ranging from the late Cretaceous Period (67 to 75 million years ago) throughout to the Oligocene Epoch (26 to 34 million years ago). Interbedded greyish volcanic ash layers, sandstones deposited in ancient river channels, red fossil soils (palaeosols), and black muds deposited in shallow prehistoric seas are testament to an ever changing landscape.

Late Holocene Fever. Credit: Christian Massari (distributed via imaggeo.egu.eu)

Late Holocene Fever. Credit: Christian Massari (distributed via imaggeo.egu.eu)

Mountain glaciers are known for their high sensitivity to climate change. The ablation process depends directly on the energy balance at the surface where the processes of accumulation and ablation manifest the strict connection between glaciers and climate. In a recent interview in the Gaurdian, Bernard Francou, a famous French glaciologist, has explained that the glacier depletion in the Andes region has increased dramatically in the second half of the 20th century, especially after 1976 and in recent decades the glacier recession moved at a rate unprecedented for at least the last three centuries with a loss estimated between 35% and 50% of their area and volume. The picture shows a huge fall of an ice block of the Perito Moreno glacier, one of the most studied glaciers for its apparent insensitivity to the recent global warming.

 Nærøyfjord: The world’s most narrow fjord . Credit: Sarah Connors (distributed via imaggeo.egu.eu)

Nærøyfjord: The world’s most narrow fjord . Credit: Sarah Connors (distributed via imaggeo.egu.eu)

Feast your eyes on this Scandinavia scenic shot by Sarah Connors, the EGU Policy Fellow. While visiting Norway, Sarah, took a trip along the world famous fjords and was able to snap the epic beauty of this glacier shaped landscape. To find out more about how she captured the shot and the forces of nature which formed this region, be sure to delve into this Imaggeo on Mondays post.

The August 2015 header images was this stunning image by Kurt Stuewe, which shows the complex geology of the Helvetic Nappes of Switzerland. You can learn more about the tectonic history of The Alps by reading this blog post on the EGU Blogs.

 (A)Rising Stone. Credit: Marcus Herrmann (distributed via imaggeo.egu.eu)

(A)Rising Stone. Credit: Marcus Herrmann (distributed via imaggeo.egu.eu)

The September 2015 header images completes your picks of the best images of 2015. (A)Rising Stone by Marcus Herrmann,  pictures a chain of rocks that are part of the Schrammsteine—a long, rugged group of rocks in the Elbe Sandstone Mountains located in Saxon Switzerland, Germany.

If you pre-register for the 2016 General Assembly (Vienna, 17 – 22 April), you can take part in our annual photo competition! From 1 February up until 1 March, every participant pre-registered for the General Assembly can submit up three original photos and one moving image related to the Earth, planetary, and space sciences in competition for free registration to next year’s General Assembly!  These can include fantastic field photos, a stunning shot of your favourite thin section, what you’ve captured out on holiday or under the electron microscope – if it’s geoscientific, it fits the bill. Find out more about how to take part at http://imaggeo.egu.eu/photo-contest/information/.

Imaggeo on Mondays: The Grand Canyon and celebrating Earth Science Week

Imaggeo on Mondays: The Grand Canyon and celebrating Earth Science Week

Today marks the start of Earth Science Week – a yearly international event which aims to help the public gain a better understanding and appreciation for the Earth Sciences. The event is promoted by the American Geosciences Institute and the Geological Society of London, amongst others, so be sure to head to their websites to find out more.

Our Imaggeo on Monday’s image celebrates Earth Science Week too, as well as the General Assembly 2015 conference theme, A Voyage Through Scales! This stunning image of the Grand Canyon was taken by Paulina Cwik.

The awe inspiring Grand Canyon is “446 km long, up to 29 km wide and attains a depth of over a mile 1,800 meters. Nearly two billion years of Earth’s geological history have been exposed as the Colorado River and its tributaries cut their channels through layer after layer of rock while the Colorado Plateau was uplifted. Visiting Grand Canyon is like a voyage through time scale”, explains Paulina.

To learn more about the geology of this geological landmark, take a look at the information available from the National Parks Service webpages, which also includes an informative video.

Imaggeo is the EGU’s online open access geosciences image repository. All geoscientists (and others) can submit their photographs and videos to this repository and, since it is open access, these images can be used for free by scientists for their presentations or publications, by educators and the general public, and some images can even be used freely for commercial purposes. Photographers also retain full rights of use, as Imaggeo images are licensed and distributed by the EGU under a Creative Commons licence. Submit your photos at http://imaggeo.egu.eu/upload/.

Imaggeo on Mondays: Layers of leg-like sandstone

John Clemens, a researcher from Stellenbosch University and one of the winners in the EGU Photo Contest 2014, opens our eyes to erosional processes in the Grand Canyon in this week’s Imaggeo on Mondays…

The photo below was taken late in the afternoon while doing some geological tourism at the Grand Canyon in Arizona, USA. The light at this time of day is ideal for such locations as it has a yellow quality and the low sun angle emphasises the contours of the land. I was on a flying visit in connection with the South-Central Regional Meeting of the Geological Society of America (held in Austin Texas). I attended this meeting because it contained a special session in honour of the work of the late Bruce Chappell and the late Alan White – two giants of late 20th century granite geology. This has nothing to do with the visit to the Grand Canyon, and even less to do with the processes that sculpted the landforms depicted.

http://imaggeo.egu.eu/view/1933/

Middle Cambrian Bright Angel Shale in the Grand Canyon, USA – one of the winning images in the EGU Photo Contest 2014. (Credit: John Clemens via imaggeo.egu.eu)

I am not a geomorphologist, but while walking along the canyon’s south rim this feature – way down towards the bottom of the inner canyon – caught my eye. Here lies the Middle Cambrian Bright Angel Shale, a variably coloured sequence of relatively soft sedimentary rocks. This lies above the more recrystallised Proterozoic rocks of the Grand Canyon Supergroup, which provide a relatively hard and stable base for the shale. Above the shale, the rocks have been stripped off by mass wasting and water erosion, leaving this vulnerable sequence exposed to the elements. There are few hard layers amongst the shale, so rain storms and snow-melt from higher altitudes combine with the desert wind to efficiently carve its shape. The shale’s remains are then washed into the inner canyon for transport down the Colorado River. In the photograph you can see a hiking trail disappearing off the edge of the inner canyon and heading steeply down to the river, through the Palaeoproterozoic regional metamorphic rocks of the Vishnu Schist.

The erosional remnant of the Bright Angel Shale has been saved (temporarily) from destruction by the presence of the slightly harder brownish layers that you can see in the image. Nevertheless, the feature is not long for this world. The harder layers that give the spider-like shape to the outcrop are nearly gone and the ridge at the top is just a narrow remnant of what was once a more extensive butte. The numerous ephemeral streams that are responsible for the canyon’s destruction are clearly visible. There terrain is decorated by only a few small green desert shrubs, which offer scant resistance to the erosion that will eventually obliterate this fantastic feature.

Since this image was captured, I have invested in some higher-quality camera equipment and have taken up high-dynamic-range (HDR) photography. Readers interested to see some of these images, including some taken during the meeting in Vienna, can have a look here.

By John Clemens, Stellenbosch University

Imaggeo is the EGU’s open access geosciences image repository. Photos uploaded to Imaggeo can be used by scientists, the press and the public provided the original author is credited. Photographers also retain full rights of use, as Imaggeo images are licensed and distributed by the EGU under a Creative Commons licence. You can submit your photos here.