5 ms·

Doesn't that increase the lake's overall temp though?

• mabbo 5y ago
  Probably not, because there's a second interesting fact about the system (which I just learned): the water isn't returned to the lake directly. Instead it's used as an input to the filtration plants, cleaned, and used as municipal water. I'm not sure what the overall effect of getting slightly warmer water in the municipal system is, but I bet it's a win overall since we spend so much energy heating up water (as per the article!). Edit: also the lake is 1600 cubic km of water, so I dunno if we could ever noticeably change the lake temperature this way.
  • kragen 5y ago
    1600 km³ × .1 kcal/ℓ is 670 petajoules, so that's the energy input you'd need to heat the lake up by 0.1°. World marketed energy consumption is about 20 TW, so the entire world economy could heat the lake up at about 0.23° per day if you covered it in a blanket first. So it's not completely out of the question, but only 2.7 million people live in Toronto, so Toronto probably only uses about 20 GW. By comparison, the lake's surface area is 19000 km², so when the sun is shining on it (at a slanting angle, as it always does that far north), it's receiving about 10 TW of solar energy, half the amount used by the entire human economy. It reflects about 10% of that into space and converts the rest into heat, then re-emits it as longwave infrared light, half at night.