Groundwater – not ice caps – is the greatest source of water on earth and most of it is ancient

0

Content of the article

THE CONVERSATION

This article originally appeared on The Conversation, an independent, nonprofit source of news, analysis and commentary from academic experts. Disclosure information is available on the original site.

——

Authors: Grant Ferguson, Professor, Department of Civil, Geological and Environmental Engineering and School of Environment and Sustainability, University of Saskatchewan and Jennifer C. McIntosh, Professor, Department of Hydrology and Atmospheric Sciences, University of Saskatchewan ‘Arizona

Advertising

Content of the article

Outside of the world’s oceans, groundwater is one of the largest reservoirs of water on Earth. Although it may seem like the planet is covered in vast lakes and river systems, they only make up 0.01% of Earth’s water. In fact, we now know that there is 100 times more groundwater on this planet than there is freshwater on its surface.

Groundwater is the water contained below the Earth’s surface. It is stored in the tiny cracks found in rock and the spaces between soil particles. It can extend deep underground, at least up to 10 kilometers.

As groundwater researchers, we are interested in how governments and industries might use these vast reservoirs of groundwater, for example to store liquid wastes and carbon dioxide. But groundwater may also have environmental functions that have yet to be revealed – this body of water remains hidden, with very few windows available to explore it.

Advertising

Content of the article

One of the largest reservoirs of water on Earth

While scientists have known for at least five decades that groundwater makes up a large portion of the world’s water, estimated groundwater volumes have focused on the upper two kilometers of the earth’s crust.

A recent analysis looking at 10 kilometers below the surface revealed that the actual volume is probably twice as large. These new estimates mean that groundwater is the largest reservoir of continental water – even more than all the water contained in the continental ice sheets of Antarctica and Greenland, which have long been considered the second largest reserves. of water from the Earth.

Previous groundwater estimates arrived at lower volumes because they only considered groundwater at shallower depths. But permeable rocks are found up to at least 10 kilometers below the Earth’s surface and can hold water in cracks and pores. Although these spaces represent only a small volume of rock mass, they total nearly 44 million cubic kilometers of water in the top 10 kilometers of rock, enough to fill more than 10,000 Grand Canyons.

Advertising

Content of the article

Groundwater is important because it can provide reliable water for homes, irrigation and industry. But these wells are generally less than 100 meters deep and rarely approach one kilometer. Most of the groundwater contained in the rock below is saline, sometimes several times saltier than seawater, and unusable for drinking water or irrigation.

Scientists know much less about groundwater stored more than a kilometer deep. Yet they determined that rain and snow that fall in North America can flow to depths of one to four kilometers. Below these depths, there are only ancient waters of other origins, whose last contact with the atmosphere dates back more than tens of thousands of years, but sometimes more than a billion years.

Advertising

Content of the article

The circulation of these deep groundwaters is controlled by the forces that drive the flow, such as topography and rock permeability. For example, rainwater and snowmelt flow deeper in mountainous regions than in flatter regions. Groundwater can flow at rates of several meters per year in sandstones and limestones, or nanometers per year in intact igneous and metamorphic rocks, due to extreme variations in the permeability of different rocks.

Environmental functions of deep groundwater

All of this has contributed to the treatment of deeper groundwater as distinct from shallow groundwater resources. For example, oil and gas producing regions often only protect groundwater to a certain depth, regardless of the strength of connections between shallow and deep groundwater.

Advertising

Content of the article

This supposed disconnect is also the basis for a number of waste isolation projects, including geological carbon dioxide sequestration, also called carbon capture and storage, and nuclear waste repositories in Canada, Finland and elsewhere.

Deep groundwater may only be loosely connected to the rest of the hydrological cycle, but that doesn’t mean it’s unimportant to the functioning of our planet. Microbes have been found in most subterranean environments with temperatures below 80°C, typical for depths of three to four kilometers. This subterranean life probably accounts for more than 10% of the Earth’s total biomass, yet the links between deep groundwater circulation and subterranean life are largely unexplored at present.

Advertising

Content of the article

There is clearly still much to learn about deep groundwater. Our windows to the deep underground are limited to deep mines, oil and gas wells and a handful of research sites.

New approaches are needed to understand deep groundwater, its environmental functions and its interactions with the rest of the hydrological cycle over deep time, both in the past and in the future.

——

Grant Ferguson receives funding from the Natural Sciences and Engineering Research Council and Global Water Futures.

Jennifer C. McIntosh receives funding from the NSF EAR (2120733), the Keck Foundation, and the CIFAR Earth4D: Subsurface Science and Exploration Program.

——

This article is republished from The Conversation under a Creative Commons license. Disclosure information is available on the original site. Read the original article: https://theconversation.com/groundwater-not-ice-sheets-is-the-larges https://theconversation.com/groundwater-not-ice-sheets-is-

Advertising

comments

Postmedia is committed to maintaining a lively yet civil discussion forum and encourages all readers to share their views on our articles. Comments can take up to an hour to be moderated before appearing on the site. We ask that you keep your comments relevant and respectful. We have enabled email notifications. You will now receive an email if you receive a reply to your comment, if there is an update to a comment thread you follow, or if a user follows you comments. See our Community Guidelines for more information and details on how to adjust your email settings.

Share.

Comments are closed.