Math Journal: Predicting lake levels

Lake Monroe water levels have started to drop.

R-OUT-Lake-Monroe-Levels-2019-Highlight July 8 2019

According to U.S. Army Corps of Engineer gauges, on July 9 at 6 a.m. the water level was 550.81 feet above sea level.

A little more than a week ago, on July 1 at 6 a.m., the lake level stood at 552.71 feet.

Why the drop? It’s because USACE is now releasing about 2,140 cubic feet of water per second through the dam into Salt Creek. Through the second half of June, only about 240 cfs was being released. But around June 29, the water levels at three points downstream on the White River had dropped low enough that more water could be released through the dam. [Data sources for Lake Monroe water levels]

The “normal pool” level of the lake is 538 feet. (It’s easy to remember, because that’s the same number of total votes available in the Electoral College.)

How long will it take for Lake Monroe water levels to be “normal”?

Of course that depends on a lot of things. One of those things is how much water the USACE lets through the dam. And that’s related to how much rain falls in the White River basin. It’s impossible to say for sure.

Still, it’s possible to make a ballpark guess. One way to make a guess is by solving a math problem. I’d guess most middle school students could probably solve it. If you’re an adult, you still might have fun working through it.

Feel free to write up your solution as a comment. If The Beacon has set up the commenting system correctly, your answer won’t spoil things for other people, because it will sit unseen, until it gets “approved.” After a month or so,  any comments with correct answers will be approved. (If this website manages to turn a buck or two, maybe correct answers to future real-world math problems will be rewarded with some kind of prize. But it’s not there, yet.)

Lake Level Problem:

On July 1 at 6 a.m. the water level was 552.71 feet.
On July 9 at 6 a.m. the water level was 550.81 feet.

Assuming the water level continues to drop at the same rate as it did between July 1 and July 9, on what date will the water level hit 538 feet? (Show your work!)

2 thoughts on “Math Journal: Predicting lake levels

  1. Sept. 1. (1) 550.81-552.71= -1.9/8 days = -.2375 feet per day. (2) 538-550-81= -12.81 feet / .2375 = 53.94 days to target normal pool level. 54 days from July 9 will be Sept 1. I want my beaches back!!

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