Will the Well Run Dry? Non-renewable Water

Ancient groundwater sources are being depleted at fast rates and the impacts of climate change are still unknown

WHO: Richard G. Taylor, Department of Geography, University College London, London, UK
Bridget Scanlon, Bureau of Economic Geology, Jackson School of Geosciences, University of Texas at Austin, Texas, USA
Petra Döll, Institute of Physical Geography, University of Frankfurt, Frankfurt, Germany
Matt Rodell, Hydrological Science Branch, NASA Goddard Space Flight Center, Greenbelt, Maryland, USA
Rens van Beek, Yoshihide Wada, Marc F. P. Bierkens, Department of Physical Geography, University of Utrecht, Utrecht, The Netherlands
Laurent Longuevergne, Géosciences Rennes, Université de Rennes 1, Rennes, France
Marc Leblanc, School of Earth and Environmental Sciences, NCGRT, James Cook University, Cairns QLD, Australia
James S. Famiglietti, UC Center for Hydrologic Modelling, University of California, Irvine, USA
Mike Edmunds, School of Geography and the Environment, Oxford University, Oxford, UK
Leonard Konikow, U.S. Geological Survey, Reston, Virginia, USA
Timothy R. Green, Agricultural Systems Research Unit, USDA-ARS, Fort Collins, Colorado, USA
Jianyao Chen, School of Geography and Planning, Sun Yat-sen University, Guangzhou, China
Makoto Taniguchi, Research Institute for Humanity and Nature, Kyoto, Japan
Alan MacDonald, British Geological Survey, Edinburgh, UK
Ying Fan, Department of Earth and Planetary Sciences, Rutgers University, New Jersey, USA
Reed M. Maxwell, Department of Geology and Geological Engineering, Colorado School of Mines, Golden, Colorado, USA
Yossi Yechieli, Geological Survey of Israel, Jerusalem, Israel
Jason J. Gurdak, Department of Geosciences, San Francisco State University, San Francisco, California, USA
Diana M. Allen, Department of Earth Sciences, Simon Fraser University, Burnaby, British Columbia, Canada
Mohammad Shamsudduha, Institute for Risk and Disaster Reduction, University College London, London, UK
Kevin Hiscock, School of Environmental Sciences, University of East Anglia, Norwich Research Park, Norwich, UK
Pat J.-F. Yeh, International Centre for Water Hazard and Risk Management (ICHARM), UNESCO, Tsukuba, Japan
Ian Holman, Environmental Science and Technology Department, Cranfield University, Milton Keynes, UK
Holger Treidel, Division of Water Sciences, UNESCO-IHP, Paris, France

WHAT: Looking at all the research on groundwater and working out what we know and what we don’t know

WHEN: 25 November, 2012

WHERE: Nature Climate Change, 2012 nclimate1744

TITLE: Ground water and climate change (subs req.)

Last month, 26 scientists all published a paper together on groundwater, which must have required either some massive Skype sessions, or people getting very sick of email chains where everyone hits ‘reply all’. As I’ve said before: science – it’s a collaborative thing.

What these researchers were trying to do was to work out exactly what we know about groundwater and how it will be affected by climate change and where the gaps are that we need to fill. Having worked in water policy, I can tell you that groundwater is normally the big unknown. Governments and organisations generally don’t have the information to know how much there is, who is taking it at what rates and how to monitor and regulate it. Generally, it gets put off until next time, while surface water rights are dealt with.

However, groundwater is estimated to be one third of all freshwater withdrawals worldwide and also the water source for 42% of the world’s agricultural water. So with climate change affecting rain patterns and shifting weather pole-ward, what will happen to groundwater? Will the well run dry in some places?

One of the biggest issues with measuring groundwater is the rate of recharge for the underground aquifers. These underwater storage vaults of water and mostly ancient water in that if you measure the isotopic composition of the water, they were likely filled thousands of years ago and have remained there without changing greatly.

Another interesting thing the isotopic analysis of the water tells us, is that if you look at the oxygen and hydrogen isotope ratios (so that’s the ratio of atoms that have different numbers of neutrons, making some heavier than others), many aquifers were filled in the late Pleistocene and early Holocene eras, around 12,000 years ago when the average temperature of the earth was around 5oC cooler than now.

Isotopic analysis: Hydrogen on the left and it’s isotope Deuterium (with the extra neutron) on the right

Isotopic analysis: Hydrogen on the left and it’s isotope Deuterium (with the extra neutron) on the right

What that means is that if those aquifers were recharging when the world was 5oC cooler than now, it’s unlikely that any recharge is taking place now or going to take place as we continue to heat our world through climate change. As the paper says ‘this non-renewable groundwater exploitation is unsustainable and is mined in a manner similar to oil’. Thousand year old water is just as renewable as million year old oil, and both are longer than a human life span.

So, what do we know about groundwater? There are two ways that groundwater can recharge: rain fed (the rain soaks into the ground) and surface water leakage (from rivers, irrigated agriculture or lakes). Both of these methods will be variable and vulnerable to climate change.

Changes in snow pack and snow distribution also impact recharge. The research currently published is still uncertain as to the extent of the impacts, but early findings are that the early start to spring is reducing the duration of recharge. Glacial retreat also impacts groundwater.

The other affects on groundwater are land use change and sea level rise inundating areas and making them salty. Managed ecosystems are not able to respond to change the way natural ecosystems can. Even if it’s a drought year, a farmer still needs to plant and crop their land. For each degree of climate change, you can roughly estimate that the equivalent climate will move 150km towards the pole. The desert of Salt Lake City will move north into the cropping areas of Idaho, and the slushy snow will move north into the ‘champagne powder’ ski regions.

More importantly, global estimates of groundwater depletion by 2050 range from 70% decreases in the Mediterranean and Brazil to increases in the Middle East and only 10% decreases in the Western US. There’s lots of uncertainty in the models as there’s a lack of data, so researchers need to extrapolate from incomplete data, resulting in large uncertainty margins.

One interesting thing I learned from this paper that I hadn’t considered before is that groundwater depletion increases sea level rise. How, you may ask? It’s the thing of living in a planetary system where everything is connected, so follow me through the water cycle here:

Thousand year old water that has been stored in the ground is pumped up a well and onto your farm. Some of the water will evaporate and the other water will grow plants, but the water has now gone into the atmospheric water cycle, so the evaporated water goes into the clouds, comes down as rain, and since 70% of our planet is ocean, there’s a really high chance the ancient groundwater will get added to the ocean. How much water? This is where it gets scary.

Groundwater water cycles (from paper)

Groundwater water cycles (from paper)

The paper talks about cubic kilometres of water. Yes, kilometres. I was unable to mentally picture that too, so I did a conversion for you. The groundwater depletion for the planet is between 145 – 204km3 of water per year, which is between 145,000 and 204,000 billion litres of water. To visualise this, you’d need to take the island of Manhattan and cover it twice with 1km deep water, which would be a depth of 4.5 Empire State Buildings end to end. This contributes between 0.4-0.5mm of sea level rise each year.

Climate change will have an effect on groundwater resources. Exactly what that is won’t be known until all the data is collected to create detailed models. However, sustainable aquifer management is going to be difficult and grow increasingly difficult as the climate continues to change.

IPCC vs Reality: Who Got it Right?

How did the projections from the IPCC 3rd and 4th reports match up against recorded temps for the last decade?

WHO: Stefan Rahmstorf, Potsdam Institute for Climate Impact Research, Germany
Grant Foster, Tempo Analytics, Garland, Maine, USA
Anny Cazenave, Laboratoire d’Etudes en Géophysique et Océanographie Spatiales, Toulouse, France

WHAT: Comparing the projections from the IPCC 3rd report in 2001 and the IPCC 4th report in 2007 to the observed climate data to 2011

WHEN: November 2012

WHERE: Environmental Research Letters Vol 7, No. 4 (2012)

TITLE: Comparing climate projections to observations up to 2011

The IPCC. It is the favourite punching bag of climate deniers and conspiracy theorists alike, who all like to claim that the reports are faulty or flawed or incorrect. So these researchers decided with the 5th Assessment Report due soon to go back to the 3rd and 4th reports, check what was in the projections and see how accurate they were on temperature rise and sea level rise. Kind of like a mid-term report card!

Five years ago, the CO2 concentration and global temperatures were closely following the projections of the IPCC 3rd report, and sea level rise was tracking along the upper limit of the uncertainty range. So where the sea level rise projections were plus or minus several millimetres a decade, the observed data was only on the plus side. How did the projections look with an extra five years of data?

The IPCC projections didn’t attempt to include the effect of solar variability, volcanic eruptions or El Niño in their temperature models because those things are random and therefore pretty impossible to predict in the future. The observed data was adjusted to remove the random variability from solar, volcanic and El Niño effects so that the researchers were comparing apples to apples when trying to assess the accuracy of the IPCC projections. For those playing at home, they used a multivariate correlation analysis (yeah, I love those too!).

The data adjustment removed the cold anomaly from the 1992/3 Mt Pinatubo eruption, and the ‘exceptionally high’ 1998 temperature maximum from the extreme El Niño event.  The observed data showed warming of 0.3oC from 1990 to 2011. The IPCC 3rd report projected 0.2-0.4oC warming to 2011 and the 4th report projected 0.3-0.5oC warming. So for temperature increases, the IPCC was pretty much spot on.

3rd report projections in blue, 4th report projections in green, observed data in red, shaded areas are the uncertainty range. (from paper)

3rd report projections in blue, 4th report projections in green, observed data in red, shaded areas are the uncertainty range. (from paper)

So what about sea level rise? The IPCC got that one wrong, but not in a way that climate deniers can celebrate – they underestimated it by 60%.

Sea level rise: measured data in red, third assessment in blue, fourth assessment in green (from paper)

Sea level rise: measured data in red, third assessment in blue, fourth assessment in green (from paper)

The IPCC best assessment was 2.0mm per year of sea level rise, and the satellite based recorded data is actually 3.2mm per year (±0.5mm error range). The researchers tried to work out if the huge difference between the projection and the recorded data was because of variability over recent decades, and decided it was unlikely because the IPCC similarly underestimated the sea level rise from 1961-2003. It was even more unlikely because the rate of sea level rise over the past 130 years has a ‘highly significant correlation with global temperature’.

This is scientist for almost identical, because those of you that read the IPCC 3rd report will remember that when the IPCC says ‘very likely’ they mean there’s a 90-99% chance it will happen. Talk about understatement.

What did the IPCC miss for sea level rise? Well firstly, it’s worth mentioning that most of the world’s scientific community didn’t expect humanity to ignore them when they warned of climate change, so their predictions were more conservative as they hoped we wouldn’t keep burning carbon at greater and greater rates as we are currently doing.

The key part though is ‘future rapid dynamical changes in ice flow’ which is scientist for big and unexpected changes, like the Arctic Death Spiral we had this summer where they found the Arctic was melting about 80 years ahead of schedule. The Arctic wasn’t supposed to be ice free in the summer from climate change until 2100, but we might get to see it as early as 2020.

What does that mean for future climate change projections? Well, it’s not pretty. So far the IPCC has been either seriously accurate (yay science!) or their worst case scenario underestimated what we’re actually doing to the planet. Which means that while the picture that the IPCC paints doesn’t look very appealing, it seems that reality could be a whole lot worse. My suggestion once again is that we stop burning carbon.


Brisbane floods 2011 (photo: Eric Veland, flickr)