Controlled Colorado River flooding released stored greenhouse gases

The 2014 experimental controlled pulse of water to the Colorado River Delta has revealed an interesting twist on how large dry watercourses may respond to short-term flooding events: the release of stored greenhouse gases. This work is reported at the Goldschmidt conference in Yokohama, Japan.

As presenter Dr Thomas Bianchi said:

“We saw a rapid release of greenhouse gases (CH4 and CO2) from the riverbed sediments to the floodwaters. These gases were largely derived from carbon which had been stored in the dry riverbed, perhaps for decades”.

Radiocarbon measurements indicate a resuspension and dissolution of trapped carbon in the riverbed that was released into the flood waters. The dissolved inorganic carbon (DIC, e.g., carbon dioxide, carbonic acid, bicarbonate, and carbonate) was found to be aged (often more than 800 years old) which would suggest that trapped CO2/IC would have been dissolved and released rapidly into the river when flooded.

Thomas Bianchi continued, “This shows that more work is needed to better understand the more unpredictable consequences of floods and droughts on aquatic ecosystems, particularly in the face of global climate change”.

The Colorado River – which carved out the Grand Canyon – is now contained by the Hoover and other dams. It is perhaps North America’s most iconic waterway. Increasing use of water from the Colorado in both the US and Mexico has meant that the Colorado Delta in Mexico, where the river runs into the Gulf of California has largely dried up. The Delta wetlands of the Colorado are now only around 1/20th of their size prior to the Hoover Dam construction.

In 2014, a major 8-week experiment released 130 million cubic metres of water from the Morelos dam (on the border with Mexico and the USA) causing a rise in river levels as far down as the delta. The pulse of water, concentrated around 27-29 March 2014, was aimed at bringing water to delta, which has been starved of water for decades. Scientists were able to look at the before and after conditions, to evaluate how future water releases might affect agricultural crops and natural plant and animal life of the lower delta.

The results of this very brief controlled flooding event showed that some of the carbon stored in the riverbed was rapidly released into the floodwaters, which although not directly measured, also likely allowed for the release of these greenhouse gases to the atmosphere. This indicates the need for a long-term approach, not just for the Colorado, but many other areas in the world that are currently experiencing human-induced changes in water flow.

According to Dr Bianchi (University of Florida) said: “Based on our findings, we suggest that stored carbon in riverbeds (e.g., greenhouse gases) is more likely to be released in a more variable climate, with floods and drought, than under more stable conditions in arid and semi-arid regions. As human needs for water resources continues to increase, the drying and rewetting of once natural river deltas may fundamentally alter the processing and storage of carbon.

There is a lot still to understand. For example, we don’t know how the duration of the wet and dry periods might affect the gas release, or whether maintaining minimum water flow levels might help.

Another factor we need to consider is whether the restored water supply would promote the growth of native plant species in the lower delta. These marsh-like plant communities capture atmospheric carbon and have the potential to store such greenhouse gases in their soils for long periods of time. There are other potential benefits too, for example the restoration of an eroding delta which would lead to coastal stability that should lead to benefits to local fisheries. Resolving these uncertainties is critical for assessing the role of inland waterways on global carbon budgets, identifying potential feedback loops under a changing climate, and planning future flow restoration events.

In practical terms, this means that restoring the river delta is not just a case of opening a tap every now and then: both the US and Mexico need to make a long-term commitment to maintain this complex delicate ecosystem, particularly in a region with such low rainfall. But we think that aiming for restoration is clearly the right thing to do”.

Commenting, Professor Elizabeth A. Canuel (Virginia Institute of Marine Science), said: “This presentation reports an unexpected finding that a short-term controlled flooding event on the Colorado River resulted in the release of greenhouse gases (CH4 and CO2) from the newly wetted riverbed sediments. Generally, production of (GHG) generated from aerobic and anaerobic respiration of organic matter is thought to be higher in dry soils, rather than wet soils. However, as this preliminary study shows, dry river sections can become “hot spots” of biogeochemical transfer and transformation when organic matter and nutrients accumulated in the sediments are “activated” during rewetting phases and first-pulse events such as this controlled flooding event.

Overall, this study provides new insights about biogeochemical responses to flood events. It also has management implications because it shows that release of GHG could be a potential unintended consequence of controlled flood events that will need to be considered against the benefits of these events in terms of restoration and/or other ecological services”.

A Mixed Response: Floodwaters return to the Colorado River but can release greenhouse gases

July 7, 2016
Rachel Wayne, UF News
floodsq

Deliberately flooding riverbeds left parched by dams has great potential to restore wetlands, but may also have a significant unintended consequence: the release of greenhouse gases.

Despite the findings, the pros of returning rivers to their natural courses and flows generally outweigh the cons, but government officials should consider the research when deciding when and how to alter river flows, said Thomas S. Bianchi, a professor of geological sciences at University of Florida and lead author on the study.

“We need to understand this as it relates to the global carbon budget,” Bianchi said.

If you’ve ever seen an Olympic-sized swimming pool, and can imagine 52,000 of them, you might begin to appreciate the amount of water that was released into the dried-out lower river delta of the Colorado River, as part of an agreement between the U.S and Mexico. Although this may sound like a lot of water, it is still less than 1 percent of what used to flow down the Colorado before all the dams were built on it.

The overall flooding experiment was supported by the U.S. Bureau of Reclamation, U.S.G.S. (United States Geological Survey), International Boundary and Water Commission/ Comisión Internacional de Límites y Agua (IBWC/CILA), and many foundations and donors. Dr. Thomas S. Bianchi, professor at UF, worked in coordination with Dr. Karl Flessa and his graduate student Hector Zamora at the University of Arizona, who led the sampling effort over the eight-week experiment. Bianchi’s group, funded by National Science Foundation- Hydrological Sciences, which included his graduate student Rory Kates and postdocs Drs. Nicholas Ward and Ana Arellano, along with Dr. David Butman at the University of Washington, and Dr. Peter Raymond at Yale University, focused on how the chemistry of the floodwaters changed over time. They found that re-wetting the dried riverbed contributed to the release of dissolved carbon and greenhouse gases (CH4 [methane] CO2 [carbon] dioxide) to the floodwaters. These increases were largely attributed to the release of these gases from the dry riverbed to the floodwaters and presumably to the atmosphere. The age of dissolved carbon coming out from the riverbed was also established using radiometric carbon dating, and indicated that some of carbon may have been stored belowground for thousands of years, and now released by the infiltration of floodwaters.

River management is conducted by the Bureau of Reclamation and IBWC/CILA and the pulse flow was released pursuant to Minute 319 of the U.S.-Mexico Water Treaty of 1944. Bianchi and his team examined how the rapid and controlled release of 130 million cubic meters of water, from the Colorado River at the Morelos Dam on the border of the United States and Mexico, mobilized carbon. The “pulse” of water temporarily flooded the delta, which had been dry for decades.

The Colorado River currently supplies water to 40 million people living in the rivershed. Heavy demand for agricultural, industrial, and municipal purposes has drained the river, which now only rarely reaches the ocean. This drainage created a dry delta near the U.S.–Mexican border, which allowed invasive plants to edge out native flora and disturbed wildlife habitat. The wetlands of the delta have been reduced to 5 percent of their original size since the construction of the Hoover Dam in the 1930s. Restoring water and sediments to the delta would help restore biodiversity to the region, supply water for agriculture, and rebuild the delta, which could help mitigate storm erosion along the coast.

Greenhouse gases, such as carbon dioxide and methane, help to trap the heat on Earth from natural radiation of the sun. Increasing levels of this atmospheric carbon have contributed to global warming. Carbon dioxide and methane concentrations in the atmosphere have increased by about 30 percent and 50 percent, respectively, since the industrial revolution. So, there remains considerable interest in understanding what controls the cycles of these gases.

Carbon dioxide is one type of inorganic carbon compound: when dissolved in water, it forms carbonic acid, which is known for its use in soda water and sparkling juice, but environmentally, contributes to ocean acidification when high levels of atmospheric carbon dioxide dissolve into the seas. Methane, an organic carbon compound, is trapped in water but easily dissipates as a gas produced by decaying organic matter.

When a large dry riverbed is flooded, these greenhouse gases are released into the water, and presumably to the atmosphere. However, re-wetting the delta may support the growth of native plants, which typically are better able to absorb and store carbon than invasive species, and may offset the carbon dioxide and methane released by flooding.

In short, Bianchi’s team and other scientists working on rivers are interested in assessing the costs and benefits of floods and droughts on natural ecosystems, particularly in a world where the climate and water cycles have become more unpredictable, in part due to global warming. Future research may examine how the duration of the flood affects water chemistry, how controlled flooding may support coastal stability and local fisheries, and how flood pulses compare to establishing a steady minimum water flow to the delta.

Bianchi to become new Editor-in-Chief of Marine Chemistry in September 2016

Marine Chemistry Journal CoverDear Editors and Board Members of Marine Chemistry,
 
As you know, Prof. Frank Millero will be stepping down as Editor-in-Chief of Marine Chemistry at the end of the year. We are of course extremely grateful to him for his excellent work and dedication to the journal and the community. Marine Chemistry is one of the top journals in the field and Frank has played a huge role in the journal’s success, along with his co-editors and editorial board. We will also be saying farewell to Frank’s Editorial Assistant, Marcie Henderson, at the end of the year. We are very appreciative and thankful of Marcie’s dedication and work on the journal. 
 
Last year I had sent an email out to all of you asking for nominations of potential editorial candidates, and also to encourage those who were interested in the role to please apply. Thank you to those who were interested and applied for the position.
 
I am pleased to announce that Prof. Thomas Bianchi, University of Florida, has accepted the role of Editor in Chief. To ensure a smooth transition and handover, he will start as of 1 September 2016 when the journal will move to our new editorial software system EVISE. I would like to welcome Tom to the journal in this new role. Tom has a lot of editorial experience as he is an editorial board member ofMarine Chemistry and he used to be an Associate Editor there before he took on a co-Editor-in-Chief position on Estuarine, Coastal and Shelf Sciences.  
 
We will send out more correspondence closer to the time, but I thought it would be good to let you know of the developments so far.
 
Kind Regards,
Dr. Luaine Bandounas
Journal Publisher Oceanography 
ELSEVIER

 

Controlled Colorado River flooding released stored greenhouse gases

Picture1The 2014 experimental controlled pulse of water to the Colorado River Delta has revealed an interesting twist on how large dry watercourses may respond to short-term flooding events: the release of stored greenhouse gases. This work is reported at the Goldschmidt conference in Yokohama, Japan.

As presenter Dr Thomas Bianchi said:

“We saw a rapid release of greenhouse gases (CH4 and CO2) from the riverbed sediments to the floodwaters. These gases were largely derived from carbon which had been stored in the dry riverbed, perhaps for decades”.

Radiocarbon measurements indicate a resuspension and dissolution of trapped carbon in the riverbed that was released into the flood waters. The dissolved inorganic carbon (DIC, e.g., carbon dioxide, carbonic acid, bicarbonate, and carbonate) was found to be aged (often more than 800 years old) which would suggest that trapped CO2/IC would have been dissolved and released rapidly into the river water when flooded.

Thomas Bianchi continued, “This shows that more work is needed to better understand the more unpredictable consequences of floods and droughts on aquatic ecosystems, particularly in the face of global climate change”.

The Colorado River – which carved out the Grand Canyon – is now contained by the Hoover and other dams. It is perhaps North America’s most iconic waterway. Increasing use of water from the Colorado in both the US and Mexico has meant that the Colorado Delta in Mexico, where the river runs into the Gulf of California has largely dried up. The Delta wetlands of the Colorado are now only around 1/20th of their size prior to the Hoover Dam construction.

In 2014, a major 8-week experiment released 130 million cubic metres of water from the Morelos dam (on the border with Mexico and the USA) causing a rise in river levels as far down as the delta. The pulse of water, concentrated around 27-29 March 2014, was aimed at bringing water to delta, which has been starved of water for decades. Scientists were able to look at the before and after conditions, to evaluate how future water releases might affect agricultural crops and natural plant and animal life of the lower delta.

The results of this very brief controlled flooding event showed that some of the carbon stored in the riverbed was rapidly released into the floodwaters, which although not directly measured, also likely allowed for the release of these greenhouse gases to the atmosphere. This indicates the need for a long-term approach, not just for the Colorado, but many other areas in the world that are currently experiencing human-induced changes in water flow.

According to Dr Bianchi (University of Florida) said: “Based on our findings, we suggest that stored carbon in riverbeds (e.g., greenhouse gases) is more likely to be released in a more variable climate, with floods and drought, than under more stable conditions in arid and semi-arid regions. As human needs for water resources continues to increase, the drying and rewetting of once natural river deltas may fundamentally alter the processing and storage of carbon.

There is a lot still to understand. For example, we don’t know how the duration of the wet and dry periods might affect the gas release, or whether maintaining minimum water flow levels might help.

Another factor we need to consider is whether the restored water supply would promote the growth of native plant species in the lower delta. These marsh-like plant communities capture atmospheric carbon and have the potential to store such greenhouse gases in their soils for long periods of time. There are other potential benefits too, for example the restoration of an eroding delta which would lead to coastal stability that should lead to benefits to local fisheries. Resolving these uncertainties is critical for assessing the role of inland waterways on global carbon budgets, identifying potential feedback loops under a changing climate, and planning future flow restoration events.

In practical terms, this means that restoring the river delta is not just a case of opening a tap every now and then: both the US and Mexico need to make a long-term commitment to maintain this complex delicate ecosystem, particularly in a region with such low rainfall. But we think that aiming for restoration is clearly the right thing to do”.

Commenting, Professor Elizabeth A. Canuel (Virginia Institute of Marine Science), said: “This presentation reports an unexpected finding that a short-term controlled flooding event on the Colorado River resulted in the release of greenhouse gases (CH4 and CO2) from the newly wetted riverbed sediments. Generally, production of greenhouse gases (GHG) generated from aerobic and anaerobic respiration of organic matter is thought to be higher in dry soils, rather than wet soils. However, as this preliminary study shows, dry river sections can become “hot spots” of biogeochemical transfer and transformation when organic matter and nutrients accumulated in the sediments are “activated” during rewetting phases and first-pulse events such as this controlled flooding event.

Overall, this study provides new insights about biogeochemical responses to flood events. It also has management implications because it shows that release of GHG could be a potential unintended consequence of controlled flood events that will need to be considered against the benefits of these events in terms of restoration and/or other ecological services”.

Constans Premiere of “Spill”

Spill, a captivating new play about the Deepwater Horizon oil spill of 2010 written by Leigh Fondakowski in collaboration with visual artist Reeva Wortel, will get its Florida premiere at the University of Florida School of Theatre + Dance’s Constans Theatre Jan. 29-Feb. 7, 2016. Directed by Tim Altmeyer, Spill is based on hundreds of interviews with Louisiana residents, fishermen, oil industry and government officials, and families of the victims of the explosion. Through poignant and deeply personal stories, the Gulf Coast becomes a nexus for the most important environmental, economic and energy policy decisions of our time. To learn more about the production, visit arts.ufl.edu/calendar.

This video discusses the play and shines light on the UF researchers (Thomas Bianchi at 3:13) and faculty whose projects relate to the Deepwater Horizon oil spill.

Video by Nicole Martins. Music by bensound.com. Historical footage by Digi Hartatak and stateofevents via archive.org.

Permafrost-eating bacteria: a new twist on thawing Arctic and global warming

Global warming is accelerating the thawing of permafrost – soil that has been at or below the freezing point of water for approximately two or more years. This releases the potent greenhouse gas methane to the atmosphere.

nysfvmkq-1443715083This direct release of methane (the main component in natural gas) occurs when methane-producing bacteria consume organic matter in the rotting soil that has been stored in permafrost over the millennia. Thus, many scientists predict large releases of methane from these sources as a result of global warming.

This is likely what you have already heard about permafrost. Indeed, most of the recent news and interest about permafrost thawing is associated with Arctic and Antarctic regions, even though alpine permafrost does exist in low latitudes as well.

What you have not likely heard about concerns an interesting twist regarding a certain type of organic matter stored in permafrost, which scientists have been talking about for the past decade. It is called yedoma, and is generally defined as organic-rich (about 2% by mass) Pleistocene-age permafrost comprised of 50% to 90% ice, by volume. Yedoma is stored in tens to hundreds of meters of permafrost in the Arctic.

We and others have recently shown that as this permafrost thaws, yedoma is released to the surrounding soils and some gets transported by rivers from land to the Arctic Ocean.

While most scientists would have predicted that this very old organic matter would not be very digestible to modern-day organisms, such as bacteria, it turns out that it is extremely “fresh” in its composition and consequently highly bio-available to microbes.

This, it turns out, has big implications for permafrost and global warming because this process produces another greenhouse gas: carbon dioxide.

Read more at
TheConversation.com