How Much Water Is Falling On Southeast Texas Right Now?
I’m a meteorologist and a professor of geography at the University of Georgia. I teach for a living, and when weather is bad I post information for my friends and the public on my Facebook page. I was asked to share the information below for a larger audience. Here goes:
Draw a triangle from downtown Houston, TX to Lufkin, TX to Port Arthur, TX and then back to Houston. This is a kind of tall isosceles triangle with a base (Houston to Port Arthur) of about 90 miles, and sides (Houston to Lufkin, and Port Arthur to Lufkin) of 120 miles. The height of this skinny triangle is about 110 miles. By simple geometry, the area of this triangle is 1/2 x base x height = about 5000 square miles.
How big is 5000 square miles? It’s double the size of Delaware. It’s almost the size of Connecticut.
How many people live in this triangle? Houston has a metro population of almost 7 million. Beaumont-Port Arthur has a metro population of 400,000. The county Lufkin’s in has a population of about 90,000 people. There are at least 7.5 million people in this triangle. Probably more. The Houston area’s been growing at a 2–2.5%/year clip. 7.5 million people is more than double the population of the state of Connecticut.
This entire area, this whole 120 x 120 x 90 square mile triangle, is predicted to have received between 32"-42" of rain, total, from Harvey by Wednesday afternoon. All of it. The whole area.
And this is just part of the overall huge precipitation area from Harvey. And the rain doesn’t stop on Wednesday, in all probability.
Let that sink in for a minute — the idea, not the water. The water isn’t sinking in anywhere in southeast Texas; it’s all running off and drowning interstates (photo above).
How much water is this? Let’s go lower-midrange and say that the average rainfall throughout this huge triangle is 36" through Wednesday at 1 pm Central time. That’s 36 inches of rain across a 120 x 120 x 90 mile triangle.
Using http://sciencing.com/do-inches-rain-gallons-water-6868160.h…:
“The total gallons of water produced by Y inches of rainfall over Z square miles is equal to 17,378,743 x Y inches x Z square miles.”
17,378,743 x 36" x 5000 square miles = 3 trillion gallons of water.
How much water is 3 trillion gallons of water? It is, in the arcane units of hydrology, almost exactly 10 million acre-feet of water (enough water to cover 10 million acres with a foot of water).
How much water is 10 million acre-feet of water? By volume, it is equivalent to 2 Lake Pontchartrains, for Louisianans. Or about 2.5 Lake Okeechobees, for Floridians. Or 4 Lake Hartwells, for Georgians and South Carolinians. Or 5 Lake Laniers, for Georgians. Or 6 Lake Martins, for Alabamians. Or 2/3 of the Great Salt Lake, or 2/3 of Lake Powell, or 1/2 of Lake Champlain. If you ranked it on the size of U.S. lakes, this volume of water would come in #25 among lakes in the United States, behind Yellowstone Lake in Wyoming, but ahead of Lake Roosevelt on the Columbia River in Washington, and well ahead of the Salton Sea in California.
Imagine pouring the volume of the 25th largest lake in the United States down onto an area about the size of the state of Connecticut with double the population of Connecticut. That’s what Harvey is doing to extreme southeast Texas. As I type.
And, again, I have for simplicity picked out just a portion of the rain area of Harvey — the part that will apparently be hit the hardest, from Houston to Port Arthur and up to about Lufkin. The total amount of water being dumped on Texas and Louisiana is more than just this.
But maybe these statistics will help you start to grasp the enormity of this situation.
However bad you think it is, it’s probably worse than that.
