We Pump Water From Underground. It Flows to the Ocean. The Oceans Are Getting Deeper.

By Sarah Zhang | May 23, 2012 8:30 am

rising sea levels

It’s easy to see how overwatering our crops would deplete the groundwater supply and cause land nearby to sink, but could it cause sea level to rise on a global scale? Yes, according to a model published in Nature Geosciences, that attributes 42% of the sea-level rise over the past half century to groundwater use.

Ninety percent of readily available freshwater is underground, and water used for drinking or crop irrigation must, of course, be brought above ground. That water then evaporates or flows into rivers, entering the water cycle and eventually the oceans, making them deeper.

Sea levels rose by 1.8 millimeters per year in the last half of the century, but calculations of the contribution from melting ice and rising sea temperatures (which causes water to expand) accounted for only 1.1 millimeters of that. This new model found that the remaining sea-level rise could be explained by groundwater depletion. Some more data is needed to prove the link conclusively, but it suggests that the global consequences of groundwater deserve a more serious look.

[via Nature News]

Image via NOAA

CATEGORIZED UNDER: Environment
  • Joe

    Proves global warming isn’t true!

  • Scott
  • Jay29

    @Joe, I hope you’re being sarcastic, because even if the figures here turn out to be true, with sea levels rising at a rate of 1.1 mm per year due just to global warming effects would still equate to a foot of water every ~38 years. That would do some serious damage to a lot of coastal cities — and that’s IF we stop sending groundwater out to sea.

  • Japhia

    Joe, it doesn’t do any such thing. These data merely indicate that *part* of the sea level increase is not due to warming and melting ice, and doesn’t at all address the myriad other data sets that point to global climate change. Way to NOT get the point of an article.

  • DB

    @Jay29, actually that would be about 1.6 inches every 38 years, or 1 foot every 275 years. I’m tempted to say that you appear to have what it takes to be a successful climate scientist ;)
    The important point is that this study further substantiates the preponderance of scientific measurements of sea level rise, indicating that it is not accelerating in recent decades due to climate warming.

  • http://backseatdriving.blogspot.com/ Brian Schmidt

    Rising sea level is a serious issue, but mostly because of future acceleration. Jay’s calculation is wrong by a factor of 10 right now (probably confusing mm with cm), but it’ll get a lot closer as warming accelerates and sea level responds.

  • randy

    One of the biggest driving forces behind most of our problems is world wide
    over population. Is anybody getting serious about this or are we once again going to
    treat just the symptoms and not the source.

  • amphiox

    As AGW continues, drought conditions will increase as surface fresh water evaporates more rapidly. This will result in increase in use of underground reservoirs, which will result in increased sealevel rise.

    So it is really academic to make a distinction about this relative to AGW. Even without such a direct link, it is still anthropogenic sea level rise both ways.

  • mike

    LOL 2012 and people still think global warming isn’t real

  • m

    LMAO – you people are nuts.

    It was ALREADY proven the change in sea levels is a result of continental drift.

    This is just another study with a political agenda. The assumption of this study – and it is a huge one – is that underground water is not replenished.

    Global warming – eeesh

    hey – why roll back the clock of physics only 100 hears? Let’s roll it back even farther to when the earth was flat!!

    Or better yet – let’s start branding people as witches because they can do long division.

    ye haw

  • Tony Mach

    As far as I can tell, all studies show that the sea level rise of the past 100 years was constant until today at range of about 2.5 mm per year to 3.2 mm per year* (there is some uncertainty about the absolute rise) – no study I know of shows an acceleration of sea level rise (be my guest, prove me wrong). I’d imagine that groundwater use has sharply increased in the past 100 years (but have no data to back that up), so if this study is close to reality (of which I am not the least sure), this would mean that the contributions to sea level rise from melting ice and rising sea temperature are declining – food for thought.

    * which would translate to something between 25 cm and 32 cm per century (100 years) – roughly a foot per century.

  • Jiminy

    It seems to me that some of the aquifers would be depleted before the sea level rose too much.

    There is already concern about depletion of large aquifers in the USA because of farming, large human populations and the diversion of ground water, being prevented from going underground and replenishing the aquifers.

    I don’t know about Africa, Asia or Europe, nor Canada.

    I do know that while around here the byword is water conservation, especially during the summer when sources are being used up. We have almost no snow pack or glacier water sources, their all lakes. Some municipalities sink wells and continue to water heavily all summer. But I assume that here, the aquifer can be replenished in the winter because of extremely high rainfall levels, assuming there are ways for the water to get into the aquifer.

  • http://discovermagazine.com Iain

    @10 m
    Groundwater does get replaced, but not nearly as quickly as it’s being used up. For instance 100 years ago in many parts of Kansas wells were only about 25 feet deep. Today those wells are at least 125 feet deep and getting deeper.

  • Brian Too

    Then our course of action is clear. We must tow the land out to sea!

  • m

    Here’s a clue

    Archimedes Principal.

    Still stuck – open a Grade 10 physics book

  • Daniel J. Andrews

    Wow. You’d think rising ocean levels caused by continental drift would feature prominently in science journals and textbooks since it is “proven”. Maybe those articles are located next to the section where the philosophy of science has been switched to proving things, not disproving.

  • Susan Courtnay

    Ground water is being depleted in most of the US at an astounding rate. We farm in southern Idaho where irrigation is king, most irrigation is from ground water pumping. Many of the wells in our area have gone dry. Our own domestic well has dropped about 25 feet in the past 15 years. Part of this is attributable to a change in irrigation practices. Flooding fields to irrigate them also helped to replenish ground water sources, but also caused much run off of water plus topsoil and chemicals. Most of our area farmers have gone to sprinkler irrigation, which saves water, but doesn’t contribute to replenishing ground water. Our winters have gotten drier (hard to tell if this is cyclic drought, which is normal here, or a longer term change) so less snow melt to help recharge aquifers as well. Most large aquifers took millions of years to form, so recharging is probably not a realistic expectation. FYI, western Canada also uses a lot of irrigation for farming and is having the same problem with reduction of ground water.
    Personally, I agree that population control is the overlooked answer to many of the worlds environmental problems. We cannot keep adding population when our resources are so finite. This should be a large part of the plan to reduce materials pollution in air, water and food sources. :)

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