No, Harvey didn't drop more water on Houston than flows over Niagara Falls in a year

John Kerry, President Joe Biden's new special envoy on climate, appeared on CNN Jan. 31 to lay out the Biden administration’s whole-of-government approach to addressing climate change.  

The cost of taking no action on climate change will far outweigh the price of preventing its worst-case scenario, Kerry argued, pointing to three recent storms — hurricanes Maria, Harvey and Irma — whose damages cost the U.S. a combined $265 billion.  

And then Kerry threw out a striking detail: "Harvey dropped more water on Houston in five days than goes over Niagara Falls in a year," he said. 

It’s true that Hurricane Harvey produced rainfall levels that have never been experienced in the U.S. in recorded history. According to Texas State Climatologist John Nielson-Gammon, the amount of rainfall that fell during a five-day period across 10,000 square miles of Texas and Louisiana exceeded the previous record set in 1899 by 62%. 

In Harris County alone, which contains the bulk of the city of Houston, the storm dropped an average 33.7 inches of rainfall across the county’s 1,777 square mile area. But is that amount of rainfall more than the volume of water that flows over Niagara Falls in a full year? 

A spokesperson for the U.S. Department of State said that Kerry’s remark was based on a 2017 Washington Post article reporting that Harvey had dumped 24.5 trillion gallons of water on Southeast Texas and southern Louisiana. 

The article also mentions, for comparison sake, that 1 trillion gallons of water flows over Niagara Falls every 15 days, and Kerry’s office used that number to extrapolate the amount of water that flows over the falls in a year. 

"A trillion gallons falls over Niagara Falls every 15 days. So, in the course of 365 days, that is about 24.3 trillion gallons of water," said state department spokesperson James Dewey.

That back-of-the-envelope calculation is correct, and it closely lines up with official estimates. Niagara Falls State Park estimates that 757,500 gallons flow over the falls each second, which is equivalent to 65.4 billion gallons per day, or 23.8 trillion gallons per year.  

In either case — be it Kerry’s estimate of 24.3 trillion gallons flowing over Niagara per year or the state park’s 23.8 billion estimate — both figures are less than the 24.5 trillion gallons of water Harvey unleashed. 

However, there’s a key detail that Kerry gets wrong. 

While it might be true that Hurricane Harvey dropped more water within a week than flows over Niagara Falls in a year, not all of that Harvey water fell on Houston or Harris County alone.  

Harvey made landfall near Rockport on Aug. 25, 2017, then drifted eastward over the next several days, dropping torrential rain on the Houston metro area. Three days later, the storm’s center moved back offshore and restrengthened over Matagorda Bay where it gained its peak intensity. Then on Aug. 30, the storm made landfall again in southwestern Louisiana moving northeastward over the southern United States while continuing to produce heavy rainfall. 

The majority of the storm’s total rainfall fell over Southeast Texas, where 60 counties were under a disaster declaration, and southern Louisiana, where 13 counties were under a disaster declaration. The storm grew weaker as it moved over Tennessee and Kentucky, where it finally dissipated. Counties in both states issued flash flood warnings as areas received up to 7 inches of rain. All told, the storm had unleashed a grand total of 33 trillion gallons of water.  

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Kerry’s statement would have been accurate if he had said Harvey dropped more water on Texas and Louisiana, or the southern U.S., over five days — instead of just Houston — than the amount that flows over Niagara Falls in a year. 

A 2018 report by the Harris County Flood Control District also made a comparison between the amount of Harvey rainfall and the amount of water that flows over Niagara Falls.  

"A total of 1 trillion gallons of water fell across Harris County over the 4 day period which would fill NRG Stadium 1,472 times and cover Harris County’s 1,777 sq. miles with an average of 33.7 inches of water. This volume of water would also run Niagara Falls for 15 days," the report said. 

After PolitiFact reached out to Kerry’s office about the misstatement, a spokesperson said that the issue has been brought up to staff and that Kerry would be more careful with that statistic. 

"In a recent interview with Fareed Zakaria on CNN, Secretary Kerry said Hurricane Harvey 'dropped more water on Houston in five days than goes over Niagara Falls in a year,'" a spokesperson said in a statement. "The statistic Secretary Kerry referenced is for water Hurricane Harvey dropped not just on Houston, but on southeast Texas and southern Louisiana."   

Kerry said on CNN that Hurricane Harvey dropped more water on Houston in five days than the amount of water that flows over Niagara Falls in a year.  

By the time Harvey dissipated it had dropped around 33 trillion gallons of water primarily on Texas, Louisiana and, to a lesser extent, Tennessee and Kentucky. By comparison, about 23.8 trillion gallons of water flows over Niagara Falls per year.  

Kerry’s comment errs in narrowing Harvey rainfall to Houston, and his office acknowledged the misstatement. In fact, 1 trillion gallons were dumped on Harris County, which would be equivalent to the volume of water that spills over Niagara Falls in 15 days.  

We rate this claim False.