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  • Results 1 to 15 of 15

    Thread: Evaporation rate?

    1. #1
      KoiFan84 is offline Senior Member
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      Evaporation rate?

      Curious as to how much water is lost each day/week due to evaporation. Is there an existing formula that takes into account maybe temperature and surface area? Does a waterfall have much effect on the amount of evaporation?

    2. #2
      simplechamp is online now Junior Member
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      I think you'd have to factor in relative humidity of the air and air movement (wind) as those will both affect evaporation rate. I was noticing this in action this past week. We had a heat wave, highs in the 90-100F range for a few days. Figured it would be a lot of evaporation. But because it was very calm and such high humidity it wasn't nearly as much as I expected. After that it cooled down to low-mid 70s. But the humidity was down and it was very windy, evaporation was actually a lot more.

      Might be able to get in the ballpark for a simple pond, but when you start getting into waterfalls, streams, etc that is really going to complicate things. Would probably have to be on a case by case basis and would get very complex.
      Last edited by simplechamp; 06-19-2022 at 11:26 PM.

    3. #3
      KoiFan84 is offline Senior Member
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      Yeah. I’m in GA. Mid to high 90s from now till September. Pretty humid though. Mine is 7.5 by 10 rectangle with a 2 ft wide sheet waterfall about 2 feet above water level. I think you’re right that it would be complicated. I have a leak due to a poor sealant so I’m trying to figure out the rate at which it’s leaking.

    4. #4
      icu2's Avatar
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    5. #5
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      Wow thats awesome, just wondering where to put the bucket with a pond with straight sides. Maybe finangle a marked stick in the water.

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      coolwon is offline Senior Member
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      My pond waters down!

      You don't notice it till you do, and then you wonder do I have leak?

      You then start wondering where it could be?
      Find more about Weather in Durban, ZA

    7. #7
      simplechamp is online now Junior Member
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      So clever and simple. Will store that one away in my memory bank, but hopefully not have to use it for a long time!

    8. #8
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      Quote Originally Posted by Craigger7 View Post
      Wow thats awesome, just wondering where to put the bucket with a pond with straight sides. Maybe finangle a marked stick in the water.
      If the pond has no shelf or step, I guess you could lay a 2x4 across one of the corners of the pond and hang the bucket from it. (Perhaps a short chain would be needed for extension depending on pond design.)

      I have not tried the bucket test, but I may need to at some point.

    9. #9
      HoschtonSawyer is offline Member
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      I too am in GA. I lose more water on hot-dry days like we've had of late for sure. 1/4" per day is not unusual, but it can be more when the weather is like it is currently.
      Good luck,

      David

    10. #10
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      Quote Originally Posted by Matt24 View Post
      If the pond has no shelf or step, I guess you could lay a 2x4 across one of the corners of the pond and hang the bucket from it. (Perhaps a short chain would be needed for extension depending on pond design.)

      I have not tried the bucket test, but I may need to at some point.


      Or I've used the post my auto feeder hangs from...

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      --Steve


    11. #11
      coolwon is offline Senior Member
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      Wind /breeze.

      Winter time.

      Lowest humidity to absorb the rising vapor?
      Find more about Weather in Durban, ZA

    12. #12
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      I loose about 200 gallons/day off a 4tier waterfall on a 4000gallon pond. Never noticed any pooling adjacent to pond or obvious leaks. I attribute such to cross wind, evaporation, etc and possibly a small non-evident leak. When I turn off waterfall in winter water loss is very minimal if at all. With that being said- my pond is autofilled by a distinct sprinkler line/zone (well water) which I have set to run 15 min every 12 hrs (ie thus roughly 200 gal/day). I don't mind this as it allows for a percentage of fresh water turnover on a daily basis and perhaps if leak small is actually there, may be feeding my surrounding landscape? Name:  IMG_1845.jpg
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      Last edited by NYkoiman; 06-24-2022 at 11:04 PM.

    13. #13
      coolwon is offline Senior Member
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      Quote Originally Posted by NYkoiman View Post
      I loose about 200 gallons/day off a 4tier waterfall on a 4000gallon pond. Never noticed any pooling adjacent to pond or obvious leaks. I attribute such to cross wind, evaporation, etc and possibly a small non-evident leak. When I turn off waterfall in winter water loss is very minimal if at all. With that being said- my pond is autofilled by a distinct sprinkler line/zone (well water) which I have set to run 15 min every 12 hrs (ie thus roughly 200 gal/day). I don't mind this as it allows for a percentage of fresh water turnover on a daily basis and perhaps if leak small is actually there, may be feeding my surrounding landscape? Name:  IMG_1845.jpg
Views: 81
Size:  210.2 KB
      Your pond appears to be very sheltered from crosswinds.

      The cascading water crashing down from tier to tier down the water fall must be responsible for a certain amount of loss.

      The multi teared waterfall must be very effective absorbing oxygen crashing down the length of it.

      Air pump,air bubbles, popping on the surface being blown away by cross winds must be responsible for the loss of water on the

      surface,for majority of ponds.
      Last edited by coolwon; 06-25-2022 at 02:44 AM.
      Find more about Weather in Durban, ZA

    14. #14
      KingstonKoi is offline Senior Member
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      I remembered seeing a formula for finding evaporation rates, so I googled that expression just now.

      The first one that comes up at https://willowridgegardencenter.com/...o-evaporation/ provides a pretty detailed formula and information. Might be worth working through.

      I always thought 100% of my daily water loss was evaporation as I have a 35 foot water stream in full sun all day that drops down to 15 feet over multiple edges. But today I found a spot where water shooting off the ledge of the waterfall is bouncing up off a rock and dampening some dirt just beyond the edge of the pond liner. Have redirected it. Will be interesting to see if it makes a difference.

    15. #15
      BWG is online now Senior Member
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      Too many variables in a water feature and weather conditions to predict evaporation through a formula. On a hot breezy low humidity day it can be significant. Showers, water falls, fountains etc. greatly increase it. Plants also contribute to evaporation loss.

      For the surface evaporation component the bucket test or a floated tub is a good predictor.
      Last edited by BWG; 06-27-2022 at 07:24 AM.

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