Hurricane Florence dumped an estimated 18 trillion gallons of water

A graphical breakdown of what the flood waters would look like in Colorado.

October 1, 2018 | By: Cathy Proctor, Jamie Reddig

The devastation left in the wake of Hurricane Florence’s pass over the southeastern United States will mark the lives of millions of people for years to come.

The storm’s winds have faded. But more than two weeks after Florence made landfall in North Carolina on Sept. 14, the stunning amount of rain dumped by the hurricane across the region is still causing damage as swollen rivers swamp towns.

At least 48 people have been killed by the storm and the aftermath. Thousands have fled their homes for shelters. Analysts believe the property damage will top $17 billion.

During its slow churn across the southeast, Florence dumped an estimated 18 trillion gallons of water across seven states in seven days, according to

That’s a huge amount of water.

By contrast, the September 2013 floods that swept across Colorado’s northeastern plains sent an estimated 60 billion gallons of water surging past the South Platte River gauges near Nebraska between Sept. 17-23 of that year, according to water engineers with the Colorado Department of Natural Resources.

Statewide in 2013, more than 18,000 Coloradans were evacuated and 10 people died in the flooding, which destroyed 1,882 structures and damaged another 16,000 buildings.

Yet Colorado’s 2013 floods, the estimated 60 billion gallons, barely register against the 18 trillion gallons produced by Florence on a chart comparing the water produced by the two incidents.

So, we wondered, what might 18 trillion gallons of water look like here?

Hurricane Florence graphic showing the impact of 18 trillion gallons of water, by Jamie Reddig.
By Jamie Reddig


With the help of statisticians at Denver Water, here’s what we learned.

Hurricane Florence’s estimated 18 trillion gallons of water would:

– Be equivalent to 14 years’ worth of average rain and snowfall in the Denver metro area, which gets an average of 16 inches of precipitation a year.

– Bury the seven-county metro area, an area that covers 4,532 square miles, in 19 feet of water, nearly touching the second-floor gutters on a two-story house if all that water came at once.

– Completely fill (from empty to full) the two biggest reservoirs in the U.S., lakes Mead and Powell, which are critical to the Colorado River and water supplies across the Southwest, and still have water left over.

– Completely fill every one of Colorado’s 1,953 water storage reservoirs seven times over, with water left over.

– Supply all the water needs of all of Colorado’s cities and towns, everyone connected to a municipal water supply, for 58 years at the current rate of use.

– Supply every water user in the state of Colorado — the cities, towns, farms, ranches, businesses and those who use wells — for 4.5 years at the state’s current rate of use.

– Cover the entire state of Colorado, 104,185 square miles, with 10 inches of water.

2 thoughts on “Hurricane Florence dumped an estimated 18 trillion gallons of water”

    1. That is a logical question to ask but it is not a simple endeavor. The reservoirs along the east coast were soon filled by Florence so the water would need to be sent to reservoirs in other regions. How would you do that at a rate to make any difference? An example that illustrates this conundrum is the Missouri River flood of 2011. In April of that year the reservoirs in the Missouri River basin were all at levels sufficient to receive and store the runoff projected from the snowpack at that time. Then it snowed and rained an equivalent of 19 inches across Montana and the Dakotas with large late snowfalls also occurring in the Poudre and South Platte River basins of Colorado. Runoff in the Missouri River ramped up tremendously and the reservoirs were all filled quickly. To avoid failure of the dams, the Corps of Engineers had to increase releases from the dams to levels never seen before. At Gavin’s Point Dam, the lowest dam on the river at the border of South Dakota and Nebraska, the previous highest release was 70,000 cubic feet per second. The Corps had to increase releases to 150,000 cubic feet per second from May through August. People asked the same question and have dreamed and schemed about how to get that water to Colorado where we need it. The problem is that to prevent the damage from that flood and save that water, you would have to either have huge empty reservoirs on the Missouri River large enough to capture and hold all that water and then pipelines to distribute that water across the country or you would have to have very large canals or pipelines, bigger than the Missouri River in flood stage, to convey the excess water to arid areas that need it and then you would need reservoirs to receive and store it at the end point. Those pipelines or canals are very expensive to build yet might be rarely used if events like Florence, Katrina, or the winter of 2011 occur only every 15 or 20 years. Also, the public have come to expect reservoirs to be multi-purpose, providing water storage, flood control, recreation, hydropower, wildlife habitat, and aesthetic functions and values to society but these purposes often conflict and decrease the ability of the reservoir to meet any one of those functions. An empty reservoir can best prevent floods and then store water and meet the other purposes but once filled has eliminated it’s potential to prevent floods. Also, in the past we have built and operated reservoirs with little thought about how it affects the ecosystem of the river on which it was built. Sometimes, our water laws don’t even allow us to ensure that that river will continue to flow and function as it should.

      I could go on and on about this subject but the bottom line is that it is a complicated issue that would take a lot of careful evaluation, planning, public support,political will, financial support, and the spirit of compromise to design, permit, build, and operate such a large project in a way that it protects and even restores the aquatic ecosystems. it seems to me that our country is too politically polarized, too self-centered, and too short sighted to ever accomplish such a project.

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