Pond Boss Forums POND CONSTRUCTION Selecting a site New pond: auxiliary water source

I am having a new pond constructed. It will be partially excavated, but with a small dam. It will have a maximum depth of 8 or 9 feet. It is probably about one acre. The main water source will be rain over about a ten acre area supplemented by a small wet-weather stream that flows during heavy rains. I am concerned that the water source may be marginal. I also have a drainage ditch about 250 feet from the pond site. Two ditches enter the main ditch in a catch basin, which empties through a corrugated pipe. I thought it would be a good idea to divert some of that water to the pond. The top of the drainage ditch is about one foot above the full-water level of the pond. My idea is to install a 6" or 8" pipe from the existing catch basin to the pond. I would install a slide gate or stop gate to block the corrugated pipe outlet. The layout of the catch basin is here:
http://www5.vetmed.auburn.edu/~branch/images/pond/HS_P8300021Labelled1.jpg . Finally my question: If I run the pipe from the ditch to the pond, should I stop the pipe at the pond's full-water level or go a little farther and stop it at about two feet below the full-water level? If I do that, then I would have about three feet of head when the ditch is full and the pond is empty. My rough calculations give a flow rate of about 300 or 800 gallons/min for 6" and 8" pipes respectively. The contractor wasn't sure it would do much good to extend the pipe's outlet below the full-water level. But it seems to me that it would--until the pond gets close to full.
Question: Is this general idea worth doing? And if so, am I correct that extending the pipe two feet below the full-water mark is going to increase the head and the flow?

Some other images of the pond construction are here: http://www5.vetmed.auburn.edu/~branch/images/pond
One image at http://www5.vetmed.auburn.edu/~branch/images/pond/HS_P8270018.jpg shows the view across the pond; the dam is to the left. The excavation is not completed on the far side. A distant view of the whole site is at http://www5.vetmed.auburn.edu/~branch/images/pond/HS_P8280009.jpg . The dam on the far side, and has been partially covered with top soil. The tree behind the tailgate of the truck is the same tree that was behind my wife and my dog in one of the other images.
Any suggestions would be appreciated.
Thanks,
Charlie

First off, Welcome to the forum!!!

To answer the ditch pipe question, the water level will balance between the pond and the ditch level....If the water in the ditch is higher than your pond, it will flow into the pond, otherwise the water will flow out of your pond into the ditch. The pipe being undewater has nothing to do with it. One thing to consider when having the pipe under water in your pond is that fish can swim out of it as the levels balance and the flow slows.

I suspect with normal rain amounts in your area, a 10 acre watershed is adequate, but your local NRCS agent should be happy to let you know for sure. Having an extra,controlable water supply could never be a bad thing!

The pond ought to look great! What species of birds are the nesting houses for?

Another thing to look into is the silt issue. It might be better to build a small little pond where the drain water collects and then flows into the main pond.

Hello FarmerCharlie and welcome to Pond Boss!

I probably didn't describe the plan accurately. Here is a sketch:

The two piping options are in brown and red. The ditch is shown full, and the pond is almost empty. From what little I remember from physics, until the level of the pond reaches the outlet of the pipe, the flow would be proportional to the head, which would be 1 foot for the brown pipe or 3 feet for the red one. Once the pond reaches the outlet of the pipe, then the head would be just the difference in levels for the ditch and the pond.

Good points. I would have the pipe entrance slightly above the pond full-water line, so there should not be any back flow when the ditch is empty. Maybe I should put a screen over the outlet to keep critters from trying to swim into the pipe.

We had a pretty severe drought here until recently, and a lot of the nearby ponds dropped severely. But even during the drought, we would get an occasional rain that would fill the ditch for a few hours. I thought that backup water source would help during dry periods.

The bird house is for purple martins. During nesting season I have WEB cameras in one of the gourds and overlooking the house. Right now the cameras are just pointing towards the pond, in case anyone wants to monitor the progress.
http://www.purplemartin.tv/charles_branch_combined/default.htm

Good point. The water in the catch basin is usually pretty clear (except during some recent road construction at the top of the hill). There is another corrugated pipe down stream a couple hundred feet. Maybe I should put my gate down there, which would create a small temporary pond during heavy rains, and would give the silt some time to settle out a little.

I think you should absolutely do it.
I would use the red pipe diagram and extend the pipe further into the pond, close to the bottom, if you can. I have two reasons to make this suggestion. First, fish will not be as likely to swim out through the pipe if it sits two or three feet off the bottom of the pond. Plus, if fresh water enters the pond into the bottom, it will likely mix with the bottom water (depending on the time of the year) and/or possibly force some of the older water upward to mix with the healthiest water of the pond. Fresh water into the top runs across the top.
I would install an AgriDrain in the ditch.

Welcome aboard farmer Charlie.

They pretty much finished the pond yesterday--just before the rains came. All that is left is the ditch project. The contractor wanted to have the entrance at the bottom of the ditch, and I wanted it at the top (so water would never flow backwards from the pond). I came up with a compromise that will let him put it at the bottom, but do it so that I could come along later and add an elbow at the entrance to raise its level. The project is going to be about $1000 for the digging and about $1000 for the 270 feet of 10" pipe he wants to use. We'll put some rip rap to deflect the flow at the outlet. With a three foot head and a 10" pipe, I expect the flow to be in the range of 1300 gal/min when the ditch is full. That's a lot of water, and it would raise the level of the pond by about 3 inches per hour. I'll post pictures when we start. Thanks to all for the suggestions.

I wish I could figure a good way to measure the actual flow. Any ideas? I thought about burying an old horse water trough at the exit of the pipe, but that seems like too much trouble.

Charles

If you are going to see the rise in pond level anywhere near where you estimate, you can use that height gain x surface area for a rough estimate of the amount of water that went in and divide it by the time consumed to make it happen.
Don't forget to carry the bum.

We got the pipe finished today. We wound up using 10" PVC pipe. The contractor was a lot more careful than I would have been. He does a lot of sewer installations, and I guess getting the slope just right is important in those jobs. Installing pipe has come a long ways since the last time I looked into it. He had a neat laser light that he setup to create a beam that went through the pipe all the way from one end to the other (270 feet) as he dug the trench. Here he is setting up the slope at the outlet point.


This shows the red laser beam shinning through the pipe at the black mark on the shovel. He aligned each section as he installed it, so the slope is very even.


Here is the view looking from the catch basin back towards the pond. I'll install an elbow at the inlet of the green pipe, so I can rotate it to control the flow and block possible backwards flow from the pond. .


Finally, here is the outlet. We'll put in some rip rap to break the flow. With a maximum 3 feet of head, the flow will probably be substantial. I am debating whether to add another section or two to carry it farther towards the bottom.



That will be the next step. I had thought about some sort of slide valve, but the flap valve looks like a better solution to me. I can hardly wait for the next gullywasher.

Looks like the workers did a god job

I thought so. I was blown away that he was able to set his laser bean at the beginning of a 270 foot run and have it still shining through the pipe when he reached the end.

And it worked to boot. We got a brief 1 inch rain the night he finished, and the pond level increased by 6 inches. We have added some rip rap at both ends since I took the pictures.

That is what we wound up doing, except the contractor talked me into putting the inlet at the bottom of the catch basin, which is below the pond's full-pool level. That means I will need to install an elbow to prevent back-flow from the pond. In the meantime I just stuck a pot into the inlet as a temporary plug to reduce the pond filling while I finished the pier/gazebo. With all the rain we have had this fall, the pond has filled a lot quicker than expected. Today it is about six inches above full pool. This shows the level almost over the top of the overflow pipe.


This morning I took a look at the catch basin, and it is also almost full. That means the pond is about a foot above the catch basin, and water is flowing backwards from the pond to the catch basin. It doesn't show up well in the image, but there is a definite eddy over what is supposed to be the inlet on the right side of the catch basin. I also have not installed the planned flap valve on the outlet of the catch basin; the catch basin is full even without the flap valve, because the drainage ditch is partially obstructed down stream on my neighbor's property.

If the rain ever ends, maybe I can get the elbow installed to eliminate the reverse flow. Although I didn't need the auxiliary filling this year, I'm sure it will help during the dry season of the more normal years.