Grant Ferguson (corresponding author), Department of Civil, Geological and Environmental Engineering, Global Institute for Water Security, and School of Environment and Sustainability, University of Saskatchewan, Saskatoon, SK, Canada; and Hydrology and Atmospheric Sciences, University of Arizona, Tucson, AZ, USA.
Jennifer McIntosh, Department of Civil, Geological and Environmental Engineering, University of Saskatchewan, Saskatoon, SK, Canada and Hydrology and Atmospheric Sciences, University of Arizona, Tucson, AZ, USA.
Oliver Warr, Department of Earth Sciences, University of Toronto, Toronto, ON, Canada.
Barbara Sherwood Lollar, Department of Earth Sciences, University of Toronto, Toronto, ON, Canada.
Christopher J. Ballentine, Department of Earth Sciences, University of Oxford, Oxford, UK.
James S. Famiglietti, Global Institute for Water Security, University of Saskatchewan, Saskatoon, SK, Canada and School of Environment and Sustainability, University of Saskatchewan, Saskatoon, SK, Canada.
Ji-Hyun Kim, Hydrology and Atmospheric Sciences, University of Arizona, Tucson, AZ, USA.
Joseph R. Michalski, Division of Earth and Planetary Science, University of Hong Kong, Hong Kong, China.
John F. Mustard, Department of Earth Environmental and Planetary Sciences, Brown University, Providence, RI, USA.
Jesse Tarnas, Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA.
Jeffrey J. McDonnell, Global Institute for Water Security and School of Environment and Sustainability, University of Saskatchewan, Saskatoon, SK, Canada, School of Resources and Environmental Engineering, Ludong University, Yantai, China, and School of Geography, Earth and Environmental Sciences, University of Birmingham, Birmingham, UK.
Comparing the relative sizes of the planets water reservoirs, groundwater– both shallow fresh water and deeper, salted water– make up about 60% of water on land, while ice sheets are close to 40%. Scientists can estimate deep groundwater volume by determining how much water various rock types, which have different porosity (quantity of empty space), can hold. Because much of this groundwater is so deep and often within rocks with very low permeabilities, the water cant quickly stream or distribute to the surface, mostly cutting it off from the planets hydrologic cycle. Areas with high elevation near low elevation can have pressure differences that let shallow water circulation to greater depths, like the water pressure created by keeping water in a water tower. Subsurface organisms basically survive on water and rocks rather of water and sunlight.
A brand-new research study approximates there are around 20 million cubic kilometers of deep groundwater, or enough to fill around 4,800 Grand Canyons. Integrated with previous estimates of shallower groundwater, the new research discovers underground water is the largest tank of water on land, measuring 44 million cubic kilometers and going beyond the volume of Earths ice sheets.
” This quote expands our practical and conceptual understanding of the amount of water that Earth holds, and it includes a whole different measurement to the hydrologic cycle,” stated Grant Ferguson, a hydrogeologist at the University of Saskatchewan who was lead author of the new research study in the AGU journal Geophysical Research Letters, which releases high-impact, short-format reports with immediate ramifications covering all Earth and space sciences.
While this deep groundwater can not be used for drinking or watering, accurate price quotes of deep groundwater volume and connection are essential for safely preparing other subsurface activities, such as hydrogen production, nuclear waste storage and carbon sequestration. Possible storage sites require to be huge enough and sealed off from surface area aquifers to avoid polluting usable, shallow groundwater.
Comparing the relative sizes of the worlds water reservoirs, groundwater– both shallow fresh water and deeper, salty water– make up about 60% of water on land, while ice sheets are close to 40%. The brand-new research study around doubled the size of the deep saline groundwater reservoir. Credit: AGU/Geophysical Research Letters
In some places the salt water has been trapped for geologic periods of time since these deep reservoirs can be detached from shallow aquifers. In addition to providing insights into past conditions in the worlds surface, these ancient waters might also support microbial communities still active today. Such deep subsurface biological communities inform mission planning for checking out potential habitable zones somewhere else in the Solar System.
Deep, salty water
Scientists can approximate deep groundwater volume by determining just how much water different rock types, which have different porosity (quantity of empty area), can hold. Previous quotes of deep groundwater between 2 and 10 kilometers only focused on crystalline rocks with low porosity, like granite. The brand-new study included the volume from buried sedimentary rocks, which are more porous than crystalline rocks, which they estimated is around 8 million cubic kilometers. Thats approximately 339 times the volume of Lake Baikal.
Since much of this groundwater is so deep and typically within rocks with very low permeabilities, the water cant easily flow or stream to the surface area, mainly cutting it off from the worlds hydrologic cycle. Areas with high elevation near low elevation can have pressure differences that let shallow water circulation to higher depths, like the water pressure developed by keeping water in a water tower.
While huge, this deep groundwater will not resolve the worlds water shortages. It is not possible to count on desalinating this salt water and using it as a source of water for drinking or irrigation, according to the research studys authors.
” We still have this limited and valuable volume of groundwater on planet Earth that we require to protect,” stated hydrologist Scott Jasechko at the University of California-Santa Barbara, who was not associated with the brand-new research study.
Life finds a way
Deep groundwater is very important for keeping waste fluids from oil and gas production and for carbon sequestration. By much better quantifying how large these deep tanks are, as well as how disconnected from shallower groundwater they are, researchers can figure out which are best to use for long-term subsurface storage.
The brand-new findings might likewise aid the look for extraterrestrial life by letting researchers study environments comparable to where microbial neighborhoods could exist on other worlds. Microbial life can make it through in a range of complex environments, from incredibly acidic conditions to heats, and deep in the Earths crust is no exception: microbes have actually been discovered as deep as 3.6 kilometers (2.2 miles) in the continental crust.
To Jennifer Biddle, a microbiologist at the University of Delaware who was not associated with the study, doubling the price quotes of deep groundwater indicates doubling the potential size of the enigmatic deep microbial biosphere too.
” If you have liquid water, theres a great opportunity that there are microorganisms there,” Biddle stated. Subsurface organisms essentially survive on water and rocks instead of water and sunshine.
That flexibility implies Martian microorganisms might be hiding at a loss planets own deep crustal groundwater, if its down there.
” If there is deep groundwater on Mars, its completely practical that if Mars was populated in the past, that deep groundwater might potentially have remnant microbes,” not unlike the ancient water on Earth, Biddle said. “So deep groundwater environments could be excellent analogues for other planetary bodies like Mars or Enceladus– a moon of Saturn– that definitely has deep water.”
Reference: “Crustal Groundwater Volumes Greater Than Previously Thought” by Grant Ferguson, Jennifer C. McIntosh, Oliver Warr, Barbara Sherwood Lollar, Christopher J. Ballentine, James S. Famiglietti, Ji-Hyun Kim, Joseph R. Michalski, John F. Mustard, Jesse Tarnas and Jeffrey J. McDonnell, 9 August 2021, Geophysical Research Letters.DOI: 10.1029/ 2021GL093549.
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Hot springs, which can source deep groundwater, are among the put on the surface where there is proof of rainwater circulating to depths of two kilometers and deeper.
New research doubles volume of salty water two to 10 kilometers underneath the surface that might save waste fluids, sequester carbon, and direct our look for extraterrestrial life.
New research more than doubles the projected volume of ancient, salted groundwater stored deep within Earths crust.
Around 24 million cubic kilometers (5.8 cubic miles) of groundwater reside within the leading 2 kilometers (1.2 miles) of Earths crust. This shallow groundwater is what we use for drinking and watering, and its primarily freshwater.