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Flood control - is it possible to use electrolysis to remove flood waters by converting water into oxygen and hydrogan gas? Is there a limit to the amount of water that can be converted at a time?

I know that this is a bit crazy and I respect what you are saying, BUT I am not trying to vaporize the entire Mississippi river, only enough to keep flood waters from ebbing into a house.

Maybe a different appreach - how about freezing the water place (in blocks) and then transporting it elsewhere

if only water was compressible....

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  • $\begingroup$ Sorry, but I'm afraid you don't know what you're talking about. That's like a least viable thing. Maybe even trying to drink it could be better. $\endgroup$ – Mithoron Oct 8 '16 at 23:20
  • $\begingroup$ Well, it's rather late for changing ideas. You could write another question, but freezing isn't a good idea. Water is simply pumped out. $\endgroup$ – Mithoron Sep 14 '18 at 21:38
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Floodwaters are immense in quantity. Let's estimate how much energy would be required to convert that quantity of water to $\ce{H2}$ and $\ce{O2}$.

  1. The Mississipi river has a (non-flood) flow rate of about 593,000 cubic feet per second, or 17000 cubic meters per second. That's $1.7 \times 10^7$ liters per second, or $1.7 \times 10^{10}$ grams per second, or roughly $10^9$ moles per second.

  2. Faraday's constant is the conversion factor between moles and Coulombs. It's value is about 96000 ampere-seconds per mol. Let's approximate it as $10^5$ ampere-seconds per mole.

  3. It takes four moles of electrons per mole of water to complete the electrolysis.

  4. Multiply the numbers together, and you get that to electrolyze all the waters of the Mississippi river, you'd need $4 \times 10^{14}$ amperes of current. That's about the amount of current present in a billion bolts of lightning. Yikes!

  5. Exactly how much voltage would be required depends on your design of electrolytic cell you use for this giga-bolt scale. Let's say it's 5 volts. That means the power you need for the electrolysis is $2\times10^{15}$ watts. That's 2000 terawatts. But the world's current total energy consumption is about 12 terawatts...

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