Pond water exit

overflow-pipeFrom the last blog post we saw water flow over a dam, yep it still stands. When we got home from shopping that morning I went straight to the pond to see how full it had gotten. The video is at the end of the post.

Here’s the deal if the rain fall is 1″ inch the pond will receive a 2″ raise. This only happens when the grounds around the pond are already saturated with water. If the ground is dry the results are 1 for 1 and sometimes less, again depending on how dry the ground is.

This particular storm dumped 3-4″ of rain and the ground was saturated double that and that is what the pond received and had to get rid of in case another storm hit.

In the picture you’ll see the normal level of the pond. In the video you’ll see the pipe under water. There is a point at which the size of pipe will no longer be able to handle the influx of water disposal. If the rain continued the spillway would be the next place for the water to exit the pond in a safe manner.

Do you have to use an overflow pipe? Not all the time but the spillway will need to be large enough to handle the overflow-pipe-1biggest rain storm you ever heard of. Remember the spillway should be wide and the fall, taper or slope away from the pond should be gradual so the water can flow out slowly. Water running too fast could start erosion.  Spillway can be seeded with grass, anti erosion screen or stoned to keep erosion from happening.

The height from the overflow pipe to the spill way and from the spillway to the top of the dam is also very important.

I am happy to say that the emergency spillway has never had water flowing across it. And have never had water over the dam. Part of the four 4″  pipes was to have an additional exit and to have a waterfall at the end so when coming home you could see the water fall and a tell tale sign if it had rained hard that day.

About the Author: Darrell Rhoades is the founder of Whatpond.com and has great expertise in building ponds. It all started when he built his own pond for the family. He writes about pond management and sell pond management products at Whatpond.com.

5 comments… add one
  • Mom Aug 15, 2009 @ 13:49

    Hey,
    Just going through some of your updates and love the pictures. They are so peaceful, calm and serene, the ones at the pond. The other ones bring back memories while you were building your pond.

  • Jim McCall Aug 17, 2009 @ 8:46

    Question regarding heavy rains and fish. Do you have any information posted regarding what happens with decorative fish (Koi) when heavy rains and spring thaws come? Just wondering if a pond will lose fish down stream due to heavy overflow or do the fish tend to stay at the bottom and avoid washing out during these times.

    Thanks,
    Jim

  • whatpond Aug 20, 2009 @ 1:21

    Hey Jim great question.
    The Koi go into a type of hibernation once the water reaches 45-50 degrees, so yes they will be towards the bottom. Spring time thaw and on rush of water is usually not a problem as they are very groggy depending on the water temp.

    As for loosing fish from the on rush of water is a possibility. The spillway is built to allow excess water to get out and never be screened to save a few fish. It is better to lose a few fish than lose the dam. The larger fish should not be lost through the overflow pipe as there should be a trash screen over the pipe. The small fry of any fish species could be lost from the rushing water, not being strong enough to handle the fast moving water.

  • Randy Klinger Feb 23, 2020 @ 7:59

    Hi Darrell,
    Just wanted to let you know we saw a River Otter in our pond 2 days in a row now. Have trailcam set up now to see if it is staying there or just passing through. Very exciting! I think it says something about the water quality in the pond. Especially if it stays. Thanks again for your help in pond management.
    Randy Klinger

  • Darrell Rhoades Feb 24, 2020 @ 4:01

    HI Randy, That does sound like a good nature event but they do eat a lot of fish so keep an eye on what transpires. Did a quick internet search and they like pretty much anything from fish to snails to fish eggs, turtles and frogs. Good lick and hope the otter works out in the best way for you.

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