Hurricane Harvey
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Harvey unloaded 33 trillion gallons of water in the U.S.

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September 2, 2017 at 10:44 p.m. EDT

Saturday evening update, Sept. 2: The overwhelming majority of Harvey’s rains are over, and we have a new calculation for the total volume of water it dispensed on U.S. soil: 33 trillion gallons. This number incorporates the rainfall not only in Texas and Louisiana, but also in Tennessee and Kentucky, which also experienced torrents.

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Thanks to meteorologist Ryan Maue, for assisting with the calculation.

Harvey is a 1,000-year flood event unprecedented in scale

Original post from Aug. 30

The latest storm totals are in, and by our estimates, about 24.5 trillion gallons of water has fallen on Southeast Texas and southern Louisiana because of Harvey.

Hurricane Harvey is the most extreme rain event in Texas history. But the city of Houston has some unique geographic and design challenges that have contributed to the flooding disaster. (Video: Daron Taylor/The Washington Post)

Breaking it down, Texas has totaled 19 trillion gallons, and Louisiana has already seen 5.5 trillion gallons. More is on the way for Louisiana, but the rain is expected to taper off Thursday.

Here’s how to help

So much rain has fallen in such a short amount of time, it will take weeks for it to fully drain. In low-lying areas and basements, it will take volunteers to physically pump the water out. Disease, unfortunately, will fester in this water as the sun comes out, and Texas summer heat returns.

It’s probably impossible to truly comprehend how much water has fallen in Texas and Louisiana. But there are comparisons we can make that help paint a picture.

First, there are 18 trillion gallons of water in the Chesapeake Bay. So that’s not even a good comparison. (Ava Marie)

If you piled up 20 trillion gallons of water over the District of Columbia (approximately 68 square miles), the height of the water would be 1,410 feet — or almost the height of the Empire State Building. (Ryan Maue)

The amount of rain that fell in Texas and Louisiana would have ended the historic California drought, twice over. (Paul Deanno)

Over Harris County alone — which is home to Houston — 1 trillion gallons of water fell in the four days from Saturday through Tuesday. That’s as much water as flows over Niagara Falls in 15 days. (Jeff Lindner)

It’s enough to cover the entire state of Arizona in more than a foot of water.

Videos: Flooding and rescues during Hurricane Harvey

Near Mont Belvieu, Tex., 51.88 inches of rain fell. That’s the highest rainfall total in any storm in the history of the United States.

  • It’s approximately how much rain falls in Houston in an entire (average) year.
  • It has taken Death Valley 23 years to accumulate that much rain. (Ian Livingston)
  • It would take Los Angeles four years to hit 52 inches. (New York Times)
  • In the arid climate of Southern California, it would take more than a decade for 52 inches of rain to accumulate
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