This report on the aftermath of Hurricane Sandy refers to the process of removing water as unwatering. However, I always thought that this process was called dewatering. What, if any, is the difference between these terms?

The dictionary does not give an entry for unwatering. But a quick google search suggests the term seems to be widely used. If unwatering is not a valid term, why is dewatering not used instead?

  • 2
    Related: english.stackexchange.com/questions/89701/…
    – Andrew Leach
    Nov 2, 2012 at 11:38
  • What does the dictionary tell you? Also, note that the MSN article clearly places unwatering within quotes. Nov 2, 2012 at 11:55
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    Congratulations for such interesting question. My reference says: "Water control is lumped into two categories—dewatering and unwatering. Water control is the removal or control of groundwater or seepage from below the surface (dewatering) or the removal or control of ponded or flowing surface water by ditches, surface drains, or sumps (unwatering)."
    – user19148
    Nov 2, 2012 at 12:13
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    @coleopterist The dictionary does not give an entry for "unwatering". But a quick google search suggests the term seems to be widely used. If "unwatering" is not a valid term, why is "dewatering" not used instead?
    – Urbycoz
    Nov 2, 2012 at 12:22
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    @coleopterist Fair enough. I've added that now.
    – Urbycoz
    Nov 2, 2012 at 12:49

4 Answers 4


The Corps of Engineers uses the term unwatering to describe removing water from locations where it is not supposed to be (subway tunnels, house basements). Dewatering describes removing water from locations where it is usually located (inside locks, river beds).

Reference: http://www.capradio.org/news/npr/story?storyid=163988271


Dewater is the usual verb that has the meaning to remove water (from).

By contrast, like many other such words, unwater more often appears in the past tense as an adjective, rather than by itself as a verb. An unwatered plant is one that has not been watered.

Usages such as (to) unwater (something) or unwatering something always sound odd and out of place, though not rare. Some dictionaries have defined unwatering as akin to dewatering.

Referring to the process of removing water as unwatering as you stated the article does, is to focus on the context: dewatering relates closely to the process, unwatering would draw attention to the site ('rendering the site better by removing water'). This is kind of a semantics-pragmatics technique. Journalese is full of such.

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    In the US Navy we used dewatering pumps in flooding emergencies (1st career). In civil engineering we dewatered flooded areas by various means (2nd career). Until today I'd never heard the term "unwater" in reference to any of these. The only example I've ever heard was the reference to an unwatered plant as above. Hopefully I never have to do this again in my third career (software).
    – delliottg
    Jul 23, 2014 at 17:55

The most frequently used term for the process of removing water is dehydration. However, as the linked definition notes, this is used for removing excess water from an object, not removing standing water.

According to this article, the difference is that "dewatering" refers to the removal of any standing water in general, where as "unwatering" is specifically "the removal of standing rainwater in shallow contaminated excavations".

You could also refer to the specific method of removal, such as pumping.


Unwatering means to draw off or remove water from a place by bucket or pump. On the other hand, dewatering is the removal of ground water from open spaces or pores in soil or rocks.

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