Pond Boss Forums GENERAL QUESTIONS Property Projects & Construction Pond drawdown

So... planning to do a bunch of work this fall on 17 to 20 acre pond built in 2003 with relatively little maintenance since. The earthen dam on the main sediment pond washed out and lots of silt built up near that area. Was good solid clay; butcouldn't withstand the volume of water going over it. Willows grew along the edges. Sediment ponds filled with sediment.

Drained it down pretty far earlier this year and started taking out some of the trees; but ground at water's edge was soft and needed excavator elsewhere. Spring rains filled it back up. I started 8" siphon and had it draining for three or four days when big storm hit. We received over 5" in about 24 hours on already saturated fields. Water was pouring in and it barely kept from going over the main dam. So... I let the siphon keep running and semi forgot about it for a few days. Went to turn it off. Probably have about 6 acres of water. Probably still over a dozen feet deep in center. Could walk to island with boots on. Can see some picnic table stuff that were blown into it during bad windstorm a couple years ago. Probably not a good situation for fish spawning. It was interesting to see where the bluegill / redear beds were. One was exactly where I thought; but the majority of beds were on a shelf about 80 feet out from bank. Never knew anything about those. Were probably in about 5' of water during normal level.

Nagging concern that sticks from trees around edges could enter and plug siphon pipe. Didn't put guard on intake end back then. Would feel better if had; but would take draining all the way or scuba diver to do now.

Will do some excavator work on island shaping wave eroded banks, taking out undesired trees that grew, and fixing better place to dock pontoon boat.

Will take out as much sediment as can in main body and sediment ponds and remaining trees from edges.

Will add pipes through main sediment pond at different levels so normally about 1.5 acres; but can contain about 2.5 acres without running over. This will slow influx into main body.

Would like to add some overflow pipes to main body into valley away from dam. That valley is currently partially farmed and partially in CRP. CRP expires this fall. One of reasons for waiting on completing. Hoping to dam that valley up and turn it into about a 4.5 acre pond.

Would like to put structure in. Have access to all the fiber optic pipe I could want from 2 to 4" diameter. I may see if can upload Google map photo. Wide open to suggestions on where and how much.

Would also like to put in dock. Wife adamant that it look nice. Have to figure out where to put it and what it'll be.

Been battling some type of blue green algae for last couple years. Stinks badly and have had known fish kills twice in last four years. Already some signs of it this year before drawdown. Will probably look at aeration this summer / fall while down.

I know the drawdown puts fish at risk. Assuming need to take out a bunch.

What all else should I be doing / thinking about?

That is already an impressive "to do" list!

Here are some hare-brained ideas that you can easily improve upon based upon your actual eyeballs on the situation:

1.) I like your sediment pond for preserving the depth in the main portion of your pond. However, if you have tilled farm ground within the watershed of your pond, then you are always going to be filling your sediment pond.

Can you easily build a couple of "dry" peninsulas near the last water flow obstacle of your sediment pond. If you can drive your trackhoe to the end of the peninsula and extend almost to the dam/obstacle and then swing your load of silt back onto dry land, then that would be perfect spacing.

If you excavated an arc of silt around each peninsula every few years, that would keep an active sediment trap available for deposition, rather than having all of it run into your mail pond.

2.) Willows are one of nature's inventions for trapping sediment. Could you allow a narrow band of willows to exist on the dam/obstacle of your sediment pond? If water during the 5" rain was actually moving, then the willows would decrease the velocity and a little more sediment would drop out earlier from the flow of water.

3.) It sounds like you do suffer some bank erosion, probably due to wave action in your large pond. One of the easiest ways to prevent shoreline erosion is to keep your pond as much as possible at the exact same water elevation. When the water is lapping at a massive root system of terrestrial plants it is difficult to cause erosion. However, when your water level drops 18" during a dry spell, then the wave action is usually able to more easily erode the bare sediments of pond slopes. Then as the water elevation goes back up, "headwall erosion" can remove material up to your normal pool elevation and actually undermine your existing erosion barriers.

If you and your wife like the look, you could even rock your banks along some of the windiest areas. Just a 12" band of rock on fabric would greatly reduce wave erosion - if the water level always stays in the rock band.

I mention that option, only because you say you might be building a second large pond a bit further downslope. That second pond could be a supplemental water source for your main pond. Pumping water up only a few feet of elevation change is MUCH cheaper than pumping from a deep well. Further, the dock and any other shoreline amenities would always be at the optimal level to keep your wife happy.

4.) Yes, it would have been nice to put a guard on your drain pipe. However, being blocked by sticks is much more likely for water surface pipes. I believe your bottom siphon pipe is unlikely to be blocked. Yes, the local flow gradient would kill a diver if he stuck his arm in the pipe at full flow. But the rate of flow drops with the cube of the distance from the pipe, so it is unlikely to draw sunken wood into its mouth.

If you are truly worried, then you could add a second shallow automatic siphon system when you work on the dam. I don't recall anyone on Pond Boss ever complaining that they had too much emergency water flow capacity!

5.) On a 20-acre pond, you almost certainly do not have enough structure. Free pipe is a good starting place. There are a lot of creative structure ideas in the archive thread where members figured out the best way to utilize their available materials. I am sure you can do the same with your pipe.

Good luck on your pond improvements! Sounds like you will be creating heaven for both fish AND family members.

Forgot to add. Farmers knifed in anhydrous ammonia to fields draining into pond hours before the 5+" rain.

Well THAT should help your algal bloom this year! (I hope your pond will benefit by that fertility increase.)

I hadn't considered creating a peninsula on the sediment ponds. Probably wouldn't be much benefit on three of the four smaller ones as can reach most with trackhoe as long as draw down some, go from both sides and drive it out a little ways. The second largest one could probably benefit and the largest one could definitely benefit. I'll have to keep that in mind. That could be an alternative to putting a drain pipe in near bottom.

Trying to eliminate willow trees around pond edge and on dams due to concern about roots in dams. I wouldn't mind some cattails, rushes, and such as long as don't get a muskrat problem. I haven't seen many. I don't know if the eagles help with those or not; but we have bald eagles' nesting in tree below the main dam.

We did buy a big 20 foot roll of the fabric and some big rock for the main dam; but don't think we have near enough. It is a little over 700 feet wide.

Cattails will draw the muskrats.

Plan on putting a primary and secondary drain in the main pond when it's drained.

Yes to remove a bunch of fish.

Plan on where the cover will go in the pond. Remember the 20% of surface area in underwater cover rule of thumb.