Fossil groundwater vulnerable to modern contamination

Study shows that over half of global groundwater is over 12,000 years old

Most of the groundwater in the world that is accessible by deep wells is fossil groundwater, stored beneath the earth’s surface for more than 12,000 years, and that ancient water is not immune to modern contamination, as has been widely assumed.

This study, led by Dr. Scott Jasechko (University of Calgary) and co-authored by an international team of researchers including Professor Richard Taylor (UCL Geography & UPGro GroFutures), is published online today (April 25) in Nature Geoscience.

Groundwater is the water stored beneath the earth’s surface in soil pore spaces and within the fractures of rock formations. It provides drinking and irrigation water for billions of people around the world.

Jasechko, Taylor and his co-researchers dated groundwater from over 6,000 wells around the globe. By measuring the amount of radioactive carbon in the water, the team was able to determine the age of the groundwater. They discovered that the majority of the earth’s groundwater is likely fossil groundwater, derived from rain and snow that fell more than 12,000 years ago. The team determined that this fossil groundwater accounts for between 42 to 85 per cent of total fresh, unfrozen water in the upper kilometre of the earth’s crust.

Until now, the scientific community has generally believed that fossil groundwater is safe from modern contamination but this study has proved otherwise.

“Deep wells mostly pump fossil groundwater but many still contain some recent rain and snow melt, which is vulnerable to modern contamination,” says Jasechko.

Rain and snow that fell after the 1950s contains tritium, a radioactive isotope that was spread around the globe as a result of thermonuclear bomb testing. Disturbingly, traces of tritium were found in deep well waters, which indicates that contemporary rain and snow melt can mix with deep fossil groundwater and, in turn, potentially contaminate this ancient water.

According to Taylor, this discovery has important ramifications that should influence the way humans use groundwater in the future,

“Our results reveal not only current use of fossil groundwater but also the potential risks to water quality associated with the use of deep wells. Indeed, we need to better understand how the construction and pumping of deep wells themselves may connect fossil groundwater to the present-day water cycle.”

Scale of global water crisis could be unknown due to inadequate metrics, study suggests #worldwaterday

Re-posted from UCL

A new study by UCL researchers exposes substantial limitations in the ability of current metrics to define ‘water scarcity’.

 

21 March 2017

A new study by UCL suggests the scale of the global water crisis could not be properly known at due to inadequacies with the current metrics used to measure it.

With today being World Water Day, the research, led by the UCL Institute for Sustainable Resources and UCL Geography, exposes substantial limitations in the ability of current metrics to define ‘water scarcity’.

The report finds that the misrepresentation of freshwater resources and demand is particularly severe in low-income countries of the tropics where the consequences of water scarcity are projected to be most severe and where most of the global population now live. Simply put, the authors argue that we do not know the dimensions of the global water crisis.

Ensuring the availability of adequate quantities of freshwater to sustain the health and well-being of people and the ecosystems in which they live, remains one of the world’s most pressing challenges. This question is reflected in UN Sustainable Development Goal 6.4 which seeks to reduce the number of people suffering from water scarcity.

The authors call for a renewed debate about how best to measure ‘water scarcity’ and argue that it be redefined in terms of the freshwater storage required to address imbalances in freshwater supply and demand. Such an approach, they contend, would enable for the explicit consideration of groundwater, the world’s largest accessible store of freshwater which accounts for nearly 50% of all freshwater withdrawals globally.

Further the authors suggest that such a metric could be used pragmatically to explore a wide range of options for addressing freshwater storage requirements beyond dams alone that include use of renewable groundwater, soil water, and trading in virtual water.

Prof Richard Taylor, co-author of the paper says:

“How we understand water scarcity is strongly influenced by how we measure it. Grossly misrepresentative measures of water scarcity can identify scarcity where there is sufficient and sufficiency where there is scarcity. An improved measure of water scarcity would help to ensure that limited resources are better targeted to address where and when water-scarce conditions are identified.”

Click here to download the paper

Authors:

Simon Damkjaer, UCL Institute for Sustainable Resources
Prof Richard Taylor, UCL Department of Geography

UPGro GroFutures: http://grofutures.org/

Photo: Irrigated maize crop supplied by groundwater in Zambia – Richard Taylor

Tropical groundwater resources resilient to climate change

Tropical groundwater may prove to be a climate-resilient source of freshwater in the tropics as intense rainfall favours the replenishment of these resources, according to a new study published in Environmental Research Letters.

Continue reading Tropical groundwater resources resilient to climate change

El Niño Monitoring in Tanzania

from Grofutures

The GroFutures team is working with the Tanzanian Ministry of Water to establish automated, high-frequency monitoring to examine how heavy rains associated with the El Niño Southern Oscillation (ENSO) replenish vital groundwater resources.

The team from Sokoine University of Agriculture (Japhet Kashaigili, PhD student Richard Festo) and UCL (Richard Taylor, PhD Student David Seddon) are working with the WamiRuvu Basin Water Office in a small semi-arid basin (Makutapora) in central Tanzania which features a wellfield that supplies the capital city, Dodoma, with safe water. Groundwater withdrawals have risen sharply in recent years and there is considerable uncertainty regarding the sustainability of this supply. Previous research led by members of the GroFutures Team showed that replenishment occurs episodically, on average just 1 year in 5, and usually in association with El Niño events.

In anticipation of the “Godzilla” El Niño event this year, the team is setting up instruments to monitor hourly groundwater levels and river stage (level) to investigate how heavy rains replenish groundwater at the Makutapora Wellfield. These observations will inform not only sustainable management of wellfield itself but also strategies for amplifying replenishment here and in other similar tropical semi-arid locations.

Commentary on UN Sustainable Development Goals

On September 25, 2015, the global development agenda for the next 15 years was set at the United Nations General Assembly following the adoption of the Sustainable Development Goals (SDGs). GroFutures Team members Simon Damkjaer and Richard Taylor comment on the limitations of current metrics used to assess progress toward SDG 6.4 – “to… substantially reducing the number of people living under conditions of water scarcity“. Read their commentary here: the Circle of Blue.

new GroFutures website

Grofutures is one of the five UPGro Consortium Projects, led by Professor Richard Taylor at University College London (UCL).  There is now a comprehensive new website that provides all the latest news and background on the study.

The Objectives of Grofutures are:

Inclusive groundwater governance:

GroFutures will develop an inclusive, participatory framework for groundwater governance in which the views of poor women and men are considered together with the trade-offs associated with groundwater development pathways.

Sustainable groundwater:

GroFutures will apply new geophysical techniques and compile long-term observations of groundwater levels from our Network of African Groundwater Observatories to substantially improve knowledge of the renewability and volume of groundwater in Sub-Saharan Africa.

Find out more at grofutures.org