New study suggests fewer resources are depleting than previously estimated, but authors urge caution in unsustainable extraction levels
UNIVERSITY OF SUSSEX
Fewer of the world’s large aquifers are depleting than previously estimated, according to a new study by the University of Sussex and UCL.
Groundwater, the world’s largest distributed store of freshwater, plays a critical role in supplying water for irrigation, drinking and industry, and sustaining vital ecosystems.
Previous global studies of changes in groundwater storage, estimated using data from the GRACE (Gravity Recovery and Climate Experiment) satellite mission and global models, have concluded that intensifying human water withdrawals in the majority of the world’s large aquifer systems are causing a sustained reduction in groundwater storage, depleting groundwater resources.
Yet this new study, published in Earth System Dynamics, reveals that depletion is not as widespread as reported, and that replenishment of groundwater storage depends upon extreme rainfall that is increasing under global climate change.
Lead author, Dr Mohammad Shamsudduha, Lecturer in Physical Geography and a member of the Sussex Sustainability Research Programme at the University of Sussex, said: “The cloud of climate change has a silver lining for groundwater resources as it favours greater replenishment from episodic, extreme rainfalls in some aquifers located around the world mainly in dry environments. This new analysis provides a benchmark alongside conventional, ground-based monitoring of groundwater levels to assess changes in water storage in aquifers over time. This information is essential to inform sustainable management of groundwater resources.”
This new study updates and extends previous analyses, accounting for strong seasonality in groundwater storage in the analysis of trends. It shows that a minority (only 5) of the world’s 37 large aquifers is undergoing depletion that requires further attention for better management.
Co-author, Professor of Hydrogeology, Richard Taylor from UCL Geography, said: “The findings do not deny that groundwater depletion is occurring in many parts of the world but that the scale of this depletion, frequently associated with irrigation in drylands, is more localised than past studies have suggested and often occurs below a large (~100 000 km2) ‘footprint’ of mass changes tracked by a pair of GRACE satellites.”
For the majority, trends are non-linear and irregular, exhibiting considerable variability in volume over time. The study shows further that variability in groundwater storage in drylands is influenced positively and episodically by years of extreme (>90th percentile) precipitation.
For example, in the Great Artesian Basin of Australia, extreme seasonal rainfall over two successive summers in 2010 and 2011 increased groundwater storage there by ~90 km3, more than ten times total annual freshwater withdrawals in the UK. Elsewhere in the Canning Basin of Australia, however, groundwater depletion is occurring at a rate of 4.4 km3 each year that is associated with its use in the extraction of iron ore.
To avoid continued depletion of aquifers, the study promotes sustainable groundwater withdrawals through augmented replenishments from extreme rainfall and ‘managed aquifer recharge’ practices.
Considering that the good Earth has had hundreds of millions of years to charge the global underground aquifer, it would be premature to say we are drastically reducing it. Perhaps in certain locales as the article points out. When we have a surplus of water such as the flooding the last few years in the midwest, that would perhaps be a good time to pumping fresh water back down in into aquifers using fracking if necessary. It would just become a storage medium that we could withdraw from in the future, like a bank. Plus it could arrest ground subsidence in areas where local extraction of groundwater is ongoing and the ground is literally sinking. Takes energy, but we have a lot of energy available, if we want it, either fossil fuels or nuclear. Water, like CO2, is the backbone of life. There is no shortage of water on the planet, only the lack of political will to develop it and use it. The Romans figured that one out and was partially why they were as successful as they were for as long as they were for hundreds of years. Because they developed their water resources.
1) Are these ‘climate change induced’ heavy rainstorms actually occurring?
2) Whenever I’ve seen (UK) TV weathermen talking about such things, they’ve said that sudden short-lived heavy rainfall doesn’t do anything for groundwater – it simply races off the surface and creates floods.
Thus we’re left wondering about this guy – does Climate Change fill aquifers OR create flooding?
3) We see Indian rice growing. I recall from easily 10 years ago, an Indian wheat farmer, on TV He was from the fertile region in the central north of India (India’s bread basket – on the volcanic soils of the Deccan Traps maybe)
In common with most farmers of that region, he used to have a borehole. It was 50 metres deep but dried up.
He sank the well to 300 metres, It was currently pumping but occasionally dried up
He was planning on taking it down to 650 metres in the then near future.
Where next? Should attractive women wearing fur-lined bikinis start watching their backs?
(I give my age away)
Not the Deccan Traps for sure – look it up in WIKI.
In Central India where I grew up, the water table came up to 30′ after each monsoon, and fell to about 60′ by the end of the dry season. The well had 3 pump platforms. This was a long time ago, but it did indicate that the water table is not necessarily a static thing, rather very labile. Don’t know about other aquifers, but all over the ancient world there are wells with 30-100 feet of steps to acomodate changing water levels.
Strange they missed the chance to demand we leave the water in the ground along with the oil, but at least they got the iron ore bad man orange right. Perhaps the authors need to be sent on a mildly corrective eco-rabies course so they get the message 100 per cent right next time.
There are some areas that aquifer depletion isn’t a joke. Like the Ogallala aquifer (spelling?) Ethanol isn’t even a joke. It’s a travesty. The land WILL subside. With no winners except the corn farmers.
Corn farmers don’t win much but the corn processing industry does. Any subsidies to “corn farmers” are actually part of someone’s plan to stabilize the supply to those lucrative job supporting taxable industrial plants. Just check the cost of a box of corn flakes, and then ask a local farmer what he would be paid for the pound of corn that went into it.