Anthropogenic climate change and ground water—we’re doing it wrong

Introduction:

Yes, climate change and global warming are happening.  Yes, this is largely the fault of us humans (it’s anthropogenic).  Unfortunately, these changes are already resulting in detrimental consequences.  Our ground water reserves, which are supremely important, are one of the adversely-impacted elements of the global climate system.  Climate change does several horrible things to ground water.

Ground water background:

The Earth with three spheres representing its fresh water
Figure 1: A graphic that represents Earth’s water as three spheres. The largest sphere is 860 miles in diameter, holds about 332,500,000 cubic miles, and represents all of Earth’s water. The middle sphere is 169.5 miles in diameter, holds 2,551,100 cubic miles, and represents all of Earth’s liquid fresh water. The smallest sphere, hovering over Atlanta, Georgia, is just 34.9 miles across, holds 22,339 cubic miles of water, and represents all of Earth’s fresh, liquid water that is not ground water. Source/Credit: USGS (Howard Perlman).

Earth is the beautiful, blue, watery princess-planet of the Sol System.  However, the vast majority of that water (99.7%) is unusable (Figure 1).  So, we should be careful with the 0.3% that we have!

Ground water supplies (held in aquifers) are the largest available source of fresh water of that all-important 0.3% (Figure 1).  I know that I get grumpy, and sometimes super-dried-up-dead when I don’t have access to water.  So, if you’re anything like me, I’ll assume that you also think ground water is important.

We all use ground water.  A lot.  Therefore, it’s important that it gets replenished.  Ground water recharge can be fed by precipitation, melt, or sometimes lakes and streams.  (Conversely, many streams, called effluent streams, are fed by the ground water, not the other way around).

As you might imagine, ground water flow is quite slow—after all, the ground is always in the way!  Thus, recharge takes a long time.  In some cases, aquifers recharge extremely slowly.  This recharge can be as low as 2mm/year (McMahon et al., 2011).  So, if we don’t monitor how much we take out of these aquifers, we won’t have them anymore.

However, we, as a society, don’t tend to worry about those pesky future-type things.  After all, as Stanislaw Jerzy Lec said: “No snowflake in an avalanche ever feels responsible.”

So, unfortunately, many aquifers are being drained and/or replaced with deeper, unusable salt water (Konikow and Kendy, 2005).  This draining can be so severe that it causes significant subsidence at the land surface (Figure 2).  This is no longer a future-problem.  We already spend a lot of time and money—and kill people—to maintain our water supplies in the face of aquifer overdraft.  The Las Vegas Associated Press reported in 2015:

“It took $817 million, two starts, more than six years and one worker’s life to drill a so-called ‘Third Straw’ to make sure glittery casinos and sprawling suburbs of Las Vegas can keep getting drinking water from near the bottom of drought-stricken Lake Mead.”

Photo of land surface subsidence from aquifer draw-down in San Joaquin Valley southwest of Mendota, California.
Figure 2: Photograph of land surface subsidence from aquifer draw-down in San Joaquin Valley southwest of Mendota, California. Source/credit: USGS.

Climate change effects on ground water recharge and vice versa:

Climate change causes direct changes in the supply of water to the land surface.  This usually means aquifer recharge rates are reduced and evaporation rates are increased.  These are both bad for ground water recharge (Treidel et al., 2011).

Recent model-based studies predict climate-change driven declines in aquifer recharge rates.  These declines are estimated at 10-20% in the southern United States (Meixner et al., 2016).  So, reduced recharge is what we are seeing in many places and what is expected to continue.  This all means less ground water.

Furthermore, reductions in ground water, which are intensified by climate change, can also exacerbate climate change!  New research has even found that anthropogenic ground-water overuse directly affects the atmosphere and weather (Zeng et al., 2017).

Climate change induced ground-water flooding:

Anthropogenic climate change also forces the global sea level to rise.  This eustatic change (i.e. changes in volume) happens for two reasons: (1) the addition of water from ice melt, and (2) the thermal expansion of the ocean water itself.

This rising sea level forces the groundwater in coastal areas to rise as well.  (Aquifers can also become salty, but that’s an issue for another post.)  In areas of low elevation this is a serious problem.  Researchers in Hawaii explain that ground water flooding from sea-level rise will be both complicated and costly:

“This flooding [just in Hawaii] will threaten $5 billion of taxable real estate; flood nearly 30 miles of roadway; and impact pedestrians, commercial and recreation activities, tourism, transportation, and infrastructure. The flooding will occur regardless of seawall construction, and thus will require innovative planning and intensive engineering efforts to accommodate standing water in the streets.”

Conclusion:

Us humans, who desperately depend on ground water reserves, are simultaneously mining aquifers much faster than they can recharge and warming the planet.  The warming exacerbates the aquifer overuse threefold by: (1) increasing drought conditions; (2) increasing evapotranspiration rates; and (3) increasing our rates of ground water use.  All the while our careless warming raises the sea level, which ironically forces our dwindling aquifers to flood us on the surface.

We should all take a moment to stare at space in disbelief or slap out a brief series of facepalms at our misuse of such an obviously important resource.  If you need help generating some disgust, consider these quick facts:

  • American golf courses are irrigated by ground water or the collection of surface water that would have become ground water. It is estimated that in 2012 US golf courses used 2.08 billion gallons of water per day.  Furthermore, golf courses in a single drought-stricken desert county near Phoenix, AZ, use 80 million gallons daily.
  • 11% of the world’s irreplaceable ground water is being mined to irrigate crops that are exported to other countries. From 2000 to 2010, exports of ground-water-exhaustive crops increased by 57% in the US, and by 70% in Pakistan.  So, increasing incentive is being applied to farmers by disassociated foreign interests to permanently mine water.

Does any of this seem like a scenario that will fix itself if we just carry on doing what we’re doing?

References:

Konikow, L. F., & Kendy, E. (2005). Groundwater depletion: A global problem. Hydrogeology Journal, 13(1), 317-320. https://link.springer.com/article/10.1007/s10040-004-0411-8/fulltext.html

McMahon, P. B., Plummer, L. N., Böhlke, J. K., Shapiro, S. D., & Hinkle, S. R. (2011). A comparison of recharge rates in aquifers of the United States based on groundwater-age data. Hydrogeology Journal, 19(4), 779. https://water.usgs.gov/nrp/proj.bib/Publications/2011/mcmahon_plummer_etal_2011.pdf

Meixner, T., Manning, A. H., Stonestrom, D. A., Allen, D. M., Ajami, H., Blasch, K. W., … & Flint, A. L. (2016). Implications of projected climate change for groundwater recharge in the western United States. Journal of Hydrology, 534, 124-138. http://www.sciencedirect.com/science/article/pii/S0022169415009750

Treidel, H., Martin-Bordes, J. L., & Gurdak, J. J. (Eds.). (2011). Climate change effects on groundwater resources: a global synthesis of findings and recommendations. CRC Press.

Zeng, Y., Xie, Z., & Zou, J. (2017). Hydrologic and Climatic Responses to Global Anthropogenic Groundwater Extraction. Journal of Climate, 30(1), 71-90. http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-16-0209.1

Jared Peters

Jared Peters

Jared Peters, PhD, is a geoscientist who specialises in marine sedimentology, marine palaeoglaciology and climate change.
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Jared Peters, PhD, is a geoscientist who specialises in marine sedimentology, marine palaeoglaciology and climate change.