A new study points to groundwater depletion being a major source of carbon dioxide emissions, with estimates that U.S. groundwater depletion could be responsible for releasing 1.7 million tonnes of carbon dioxide to the atmosphere every year.
Humans may be adding large amounts of carbon dioxide to the atmosphere by using groundwater faster than it is replenished, according to new research. This process, known as groundwater depletion, releases a significant amount of carbon dioxide into the atmosphere that has until now been overlooked by scientists in calculating carbon sources, according to the new study.
The study’s authors estimate groundwater depletion in the United States could be responsible for releasing 1.7 million tonnes of carbon dioxide to the atmosphere every year.
Based on these figures, groundwater depletion should rank among the top 20 sources of carbon emissions documented by the US Environmental Protection Agency (EPA) and the Intergovernmental Panel on Climate Change (IPCC). This would mean the carbon dioxide emitted through groundwater depletion is comparable to the carbon generated from aluminum, glass, and zinc production in the United States, according to the study’s authors.
“We were somewhat surprised that this hasn’t been accounted for in the literature and in the [EPA and IPCC] evaluations,” said David Hyndman, a hydrogeologist at Michigan State University in East Lansing, Michigan and co-author of the new study accepted for publication in Earth’s Future, a journal of the American Geophysical Union.
Groundwater depletion’s impact on carbon emissions is significant yet relatively small compared to the leading contributors, according to the authors. For example, scientists estimate fossil fuel combustion in the United States is responsible for releasing more than 5 billion tonnes of carbon dioxide into the atmosphere every year, close to 3,000 times the amount released from groundwater depletion. Still, the study authors argue that understanding all sources of carbon dioxide emissions is important for making accurate climate change projections and finding solutions.
“It’s not going to change the way we think about global climate change. It’s just another factor involved that we need to consider,” said Warren Wood, a hydrogeologist at Michigan State University and co-author of the new study.
“This is an idea that a number of us have knocked around a little bit, but I think the approach here is really novel,” said Bill Simpkins, a hydrogeologist at Iowa State University in Ames, Iowa who was not involved in the study. “[Groundwater depletion] is certainly not a documented source that people feel obligated to put in their climate estimates.”
Groundwater’s Carbon Cycle
Rain falling from the sky contains the same amount of carbon dioxide as is present in the atmosphere. But soil carbon dioxide levels are up to 100 times greater than carbon dioxide levels in the atmosphere, because soil microbes degrade organic carbon into carbon dioxide. When rainwater hits the ground and percolates through Earth’s rocks and sediments, the water dissolves extra carbon produced by these microbes.
If left to its own devices, this carbon-rich water remains below ground for hundreds to thousands of years before surfacing in oceans or freshwater bodies. But humans are now extracting groundwater at an unprecedented pace to sustain a growing population. The United States alone sucks up nearly 80 billion gallons (303 billion liters) of water from the earth every day to supply drinking water and irrigate crops, enough water to fill Utah’s Great Salt Lake five times every year.
Analysing Depletion’s Impact
Wood’s research has largely focused on the hydrogeology of arid areas, but he recalls suddenly coming up with the concept for the new study one morning after coffee. “It came to me at about 9:30 a.m. and by 11:30 a.m. I had the first draft of the manuscript done,” Wood said.
In the new study, Wood and Hyndman analyzed groundwater depletion and groundwater carbon chemistry data from the U.S. Geological Survey (USGS) to calculate how much carbon dioxide is likely transferred from groundwater to the atmosphere each year.
USGS scientists estimate that the United States annually depletes 25 square kilometers (9.7 square miles) of groundwater, which contains roughly 2.4 million metric tons (5.2 billion pounds) of bicarbonate. Wood and Hyndman then conservatively assumed that half of the released bicarbonate is converted to atmospheric carbon dioxide.
From this information, Hyndman and Wood estimated the U.S. releases approximately 1.7 million metric tons (3.8 billion pounds) of carbon dioxide a year into the atmosphere from groundwater depletion. This is more than the amount of carbon dioxide produced by the generation of electricity used to power 250,000 households in the United States each year.
Scientists know less about groundwater depletion on a global scale, but Wood and Hyndman predict groundwater depletion releases 9.7 to 13.5 million metric tons (21.4 to 29.8 billion pounds) of carbon dioxide to the atmosphere each year globally.
“This linkage between subsurface water and the atmosphere is a very creative and original synthesis. I’m not aware of anyone who has even suggested this in the past,” said Lenny Konikow, a scientist emeritus at the U.S. Geological Survey who was not involved with the study.
The researchers note that this study is still just a preliminary step, but they hope their study will provoke in-depth research on the role of carbon dioxide from groundwater depletion.
“If we can understand how humans are having an effect, hopefully we can take that next step and try to mitigate some of these effects,” said Hyndman.
American Geophysical Union media release, 16 Nov 2017
Last chance to register for the 2017 NCGRT IAH Distinguished Lecture presented by Dr Glen Walker
Climate Change and Australian Groundwater: Current State of Knowledge and Future Responses
The climate shift in south-western Western Australia and the Millennium Drought has highlighted the need to better understand how water resources will be affected by changing climate across Australia. Australia has long experience with managing water resources in a variable climate. This, together with the Water Reform has meant that Australia is well placed, compared to other countries, to meet the challenges to groundwater management.
This talk will provide an overview of the results from recent projects around Australia and will be supported by local panellists in each state contributing to the discussion.
Adelaide: Oct 5
Canberra: Oct 10
Melbourne: Oct 17
Darwin: Oct 26
Sydney: Oct 31
Brisbane: Nov 1
Perth: Nov 9
A video link will be provided to Hobart and Townsville delegates.
Click here for venue and registration information
The National Centre for Groundwater Research and Training and International Association of Hydrogeologists are pleased to have Dr. Rebecca Nelson as the 2016 NCGRT / IAH Distinguished Lecturer.
Dr. Nelson will tour every state and territory in Australia to deliver her lecture entitled: Regulating the cumulative impacts of groundwater withdrawals: Australia and further afield.
Abstract: The regulation of groundwater extraction has shifted dramatically through an intense era of intense water reforms spanning three decades. A key outstanding issue is controlling withdrawals with an eye to their cumulative impacts on groundwater resources and dependent systems. Such control is complicated not just by the incremental additive effects of many small withdrawals, but also by interactive and synergistic effects. This complexity is intensified further by data paucity, potentially significant time lags, and simultaneous background changes to natural systems, such as those caused by climate change.
Read the full abstract here.
Melbourne: 18 October
Hobart: 20 October
Perth: 26 October
Townsville: 2 November
Brisbane: 3 November
Canberra: 10 November
Sydney: 10 November
Adelaide: 30 November
Darwin: 1 December
Click here to register via the NGCRT website.
Dr Wilson’s biography is available here.
The 2017 bi-annual Australasian Groundwater Conference is being convened by IAH and UNSW in Sydney, 11-13 July, 2013.
The theme for the conference will be Groundwater Futures: Science to Practice.
An engaging three-day event is planned that will enable delegates to examine the multi-dimensional challenges affecting the sustainable development of the regions groundwater resources.
Engaging panels, informative presentations, exhibitions and networking opportunities will engage the over 300 delegates from Australasia’s groundwater research, industry, and management and policy organisations.
2017 AGC Abstract themes:
- Emerging Groundwater Initiatives
- Groundwater Science and Future Innovations
- Interdisciplinary Groundwater Problems
- Groundwater Resources and Climate Change
- Energy and Groundwater
- Groundwater Quality and Human Health
Abstracts will open December 1 2016 and close March 1 2017.
Keynote, plenary presentations and panel sessions will include climate change and groundwater resource challenges, energy futures, social license to operate and future directions and innovation in groundwater.
Stay tuned for the launch of the AGC2017 website.
Dr. Wendy Timms Chris McAuley
AGC2017 Conference Chair IAH President
Geoscience Australia has recently released the most comprehensive mapping report on Australia’s largest groundwater basin.
The report has been developed in the form of an Atlas – providing valuable information to assist water managers and communities to make more informed decisions towards sustainable management of this vast water resource. The Hydrogeological Atlas of the Great Artesian Basin (Basin) draws together geological and hydrogeological data collected from the area and condenses it into a series of 55 maps, making the information much more accessible to water managers, researchers, industry, farmers, community groups and the general public.
Australia is the driest inhabited continent on the Earth and, per capita, is one of the largest users of water in the world. Australia draws upon a combination of surface water and groundwater for agriculture production, industry (including mining activities), and town and domestic supply. In many parts of Australia, groundwater is the only reliable water resource, and careful planning and management is critical to ensure sustainable use of this valuable water supply.
The Great Artesian Basin covers most of Queensland, the north western parts of New South Wales, part of the Northern Territory and about half of South Australia. The Great Artesian Basin is Australia’s largest groundwater system. Comprising around 20% of Australia’s total landmass, the Basin covers most of Queensland, the north western parts of New South Wales, part of the Northern Territory and about half of South Australia. It is estimated to hold nearly 65,000 million megalitres of water, (about 130,000 Sydney Harbours) and is a key source of water for springs, many of which support unique ecosystems.
Find out more about the Atlas and its development here.