wa·​ter·​shed | \ ˈwȯ-tər-ˌshed How to pronounce watershed (audio) , ˈwä- \
plural watersheds

Definition of watershed

1a : a dividing ridge between drainage areas : divide entry 2 The watershed of the Himalayas does not lie along the line of its highest peaks, as in most mountain ranges, but about a hundred miles farther north.— Frits Staal
b : a region or area bounded peripherally by a divide and draining ultimately to a particular watercourse or body of water the Mississippi River watershed
2 : a crucial dividing point, line, or factor : turning point This year marked a watershed for contemporary classical music in the city.The Chicago Tribune The spring of 1949 was, in general, a watershed in Joe Liebling's life.— Raymond Sokolov The death of Ugandan teacher Gregory Byaruhanga at the hands of the Kenyan police has marked a watershed in the rising tension in the region and in the instability of the Kenyan regime.— Victoria Brittain often used before another noun a watershed momenta watershed eventThe watershed year for science fiction must be 1968, when Stanley Kubrick's 2001: A Space Odyssey appeared, not only dramatically expanding for this kind of motion picture the potentials of film technology, but making science fiction a vehicle for both poetic vision and metaphysical exploration.— Ira Konigsberg
3 British : the time of day after which television programs not appropriate for children may be broadcast the nine o'clock watershed
4 medical : an area of tissue (as of the brain or colon) that is located at the periphery of two separate arterial systems, is dependent on both for blood supply, and may be poorly perfused and vulnerable to ischemia usually used before another noun Brain imaging of patients with vascular dementia typically show small strokes or poor blood supply deep in the brain, at the natural terminal (the so-called watershed area) of the blood vessel.— Renee Meyer… cell death caused by blocked blood flow in the brain's "watershed" region, where two arteries supply blood.— Susan Scutti — see also watershed infarction

Watershed Has Geographic Origins

Opinion on the literal geographic meaning of watershed is divided. On one side of the debate are those who think the word can only refer to a ridge of land separating rivers and streams flowing in one direction from those flowing in the opposite direction. That's the term's original meaning, one probably borrowed in the translation of the German Wasserscheide. On the other side of the argument are those who think watershed can also apply to the area through which such divided water flows. The latter sense is now far more common in America, but most Americans have apparently decided to leave the quarrel to geologists and geographers while they use the term in its figurative sense, "turning point."        

Examples of watershed in a Sentence

The show will not air until after the nine o'clock watershed. a watershed moment in her life came when she inherited a reasonable sum of money and was able to start her own coffee shop
Recent Examples on the Web In all, some 40 tons of slow-release calcium pellets were dropped over a 29-acre watershed in October 1999, and the experiment has been running ever since. James Bruggers, The Courier-Journal, 5 Jan. 2022 Zebryk brought along an increment borer, a specialized extraction tool for making field estimates on the age of a tree based on its rings, and the two tramped along the watershed. Jonny Diamond, Smithsonian Magazine, 5 Jan. 2022 Labor members think the Starbucks union effort marks a watershed for the workers' movement. NBC News, 9 Dec. 2021 In 2019, the Museum Fire burned a little under 2,000 acres on one watershed in Flagstaff. Zayna Syed, The Arizona Republic, 30 Nov. 2021 Without salmon, life along the entire watershed starts to unravel. Los Angeles Times, 20 Dec. 2021 Prairie Mountain, a Coast Range peak to the west, influences the Lower Long Tom watershed’s climate by diverting cooling maritime winds to the north and south. Michael Alberty | For The Oregonian/oregonlive, oregonlive, 18 Dec. 2021 Restoring the property will reduce nitrogen and phosphorous loading in the watershed, which can contribute to harmful algal blooms -- an issue that has plagued Lake Erie in recent years. Mary Jane Brewer, cleveland, 24 Nov. 2021 The state’s principal watershed, the Sierra, has changed substantially. George Skelton, Los Angeles Times, 21 Oct. 2021

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'watershed.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

See More

First Known Use of watershed

1764, in the meaning defined at sense 1a

Learn More About watershed

Time Traveler for watershed

Time Traveler

The first known use of watershed was in 1764

See more words from the same year

Listen to Our Podcast About watershed

Dictionary Entries Near watershed

water shamrock


watershed infarction

See More Nearby Entries 

Statistics for watershed

Last Updated

12 Jan 2022

Cite this Entry

“Watershed.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/watershed. Accessed 20 Jan. 2022.

Style: MLA
MLACheck Mark Icon ChicagoCheck Mark Icon APACheck Mark Icon Merriam-WebsterCheck Mark Icon

More Definitions for watershed



English Language Learners Definition of watershed

: a time when an important change happens
: a line of hills or mountains from which rivers drain : a ridge between two rivers
: the area of land that includes a particular river or lake and all the rivers, streams, etc., that flow into it


wa·​ter·​shed | \ ˈwȯ-tər-ˌshed How to pronounce watershed (audio) , ˈwä- \

Kids Definition of watershed

1 : a dividing ridge (as a mountain range) separating one drainage area from others
2 : the whole area that drains into a lake or river

More from Merriam-Webster on watershed

Nglish: Translation of watershed for Spanish Speakers

Britannica English: Translation of watershed for Arabic Speakers

Britannica.com: Encyclopedia article about watershed


Test Your Vocabulary

Farm Idioms Quiz

  • cow coming home
  • What does 'poke' refer to in the expression 'pig in a poke'?
True or False

Test your knowledge - and maybe learn something along the way.

Universal Daily Crossword

A daily challenge for crossword fanatics.

Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!