Pond Boss Forums INTRO Questions & Observations Considerations for a dual level pond

It's getting near to the point where trees will be cleared from the site for Cindy's pond. The contract with the pond builder specifies 2 siphon spillways at 2 different levels. At full pool the pond will be 6-7 acres and I'm planning on making the other pool level 3 feet lower.

To make it easier to design I've been thinking in terms of a pond within a pond. It's possible that the lower level could become the permanent level depending on rainfall amounts, how well the pond seals, and what the watershed ultimately provides. For this reason I want to design so that the pond will look good and function well at the lower level. It's also possible that the high pool level will become the permanent depth. If the weather returns to our usual 50+ inches of rain/year and the ponds holds water sufficiently, it would be likely that we could keep it full. The best result would be to have the option of choosing either level.

My vision of the smaller (lower siphon level) pond is a traditional one with no living trees submerged and rimmed banks. Moving up the banks from the shoreline would be a slope of around 4 to 1.

The vision for the larger pond footprint has the (4 to 1) banks flooded. Also flooded would be an area of 1/2 to 3/4 acres that would not have been cleared. There are several large trees in that area including Swamp Tupelo, Sweetbay Magnolia, Sweet Gum and Water Oaks.


I understand that most of the trees in the swamp area would not survive more than brief flooding. It's possible that the Tupelos could survive if the flooding was gradual and in fact many of the larger ones are growing in the creek that feeds the ponds. I know that even periodic flooding may kill all of the trees and that no one knows for sure.

If we end up maintaining the pond at the lower level we will have a tradition design with the usual considerations.

If we have the ability to maintain the high water level and choose to do that, what might be some of the issues created by the flooded area? I already know that the gradual banks will encourage aquatic weeds, but I'm curious about what to expect from the standing timber in the swamp. I've seen ponds with extensive areas of flooded trees, but I haven't seen it discussed much here. I'm curious whether there are positive aspects to the flooded timber that might offset the high levels of decaying material it represents. The average depth of the swamp area would be about 2 feet.

Finally, I'm trying to imagine what the possibilities are for this design if we have the ability to change the level, at least seasonally. Can I manage some weed problems by changing depth? Can I improve or limit spawning beneficially? What influence could we have on the balance of animal life in general?

The goals for this pond include fishing, but that isn't the primary one. The best way I can think to describe our main goal is a combination of wildlife habit and aesthetics. To clarify this somewhat I'll mention that Cindy almost bought a property with a significant area of Tupelo swamp. Aesthetics to her is an environment that looks like it was naturally occurring as much as possible, and where wildlife in general is balanced and abundant. In other words, this pond doesn't need to produce trophy fish or attract game specifically for hunting to be successful in the owner's eyes.

Any ideas or comments would be appreciated.

GW,
Most of the ponds in my neighborhood are designed that way, mine being one of the few exceptions. I didn't understand what the digger was trying to tell me so I just said no. Not the best decision. My water level varies up to 40 inches from the wet season to the dry. If I ever get around to another pond it will be as you describe. I have a a legume ground cover that grows fast enough to keep up with the receding water and the fish eat it as the water rises.

I would go with bald cypress trees. I have 15+ on my property and everyone thinks they are beautiful. They grow extremely well in several feet of water.

In the fall the needles turn a golden brown and then drop off. Great if you like the changes of color.

That's interesting Rad. Do your neighbor's all use the two levels at the same time with the same goals?

Are they able to manage aquatic weeds by manipulating the pool level?

Do they effect fish spawning (limit or increase) with pool level?

I'm curious what someone who is used to having two drains might say they're giving up by having only one.

GW, If the slope is 4:1 ratio (or lower) - you can more easliy mow down to the lower level to control vegitation around the edges of the pond.

My dam was 3:1 and I couldnt safely mow it, too steep.

edited to fix my numbers.

I was trying to get close to a 3:1 slope in my diagram. I had started out with a more gradual slope, but I thought it might make fishing difficult when the banks were flooded. On the other hand I would like Cindy to feel comfortable mowing...

I would really appreciate it if other people would comment about the slope of the bank as well. When the pond man starts shaping the bottom I would like to give him a specific ratio to shoot for.

Thanks.

GW, oops. yes numbers were switched. I fixed them.

I was thinking how easy it would be to run around and mow the pond while at the lower level...nice design.

GW, I will add one comment about slopes of 4:1 or greater (which I have on my big pond). Some sections of my pond are so gradual that I end up up with lots of uncontrolable vegitation. Now that is and advantage in some ways but it makes it more difficult to get a nice clean cut water line.

The sections of my pond that are really shallow, say 1 - 2 feet deep with very little to no slope, hold the greatest numbers of fish for most of the year. Thats where a majority of spawing beds are at too.

Can you hear me talking out of both sides of my mouth?

I will say that there is something magical about reeling a lure across a 1 foot deep section of water and seeing the swirl then the explosion of a LMB hooking up.

I like your idea of flooded areas - maybe that where you will get the shallows.

GeeDub,
Rocky-T and I were discussing this some time ago right after my excavator finished our project. The subject focus was the front perimeter of the building site pad we built up. My contractor put the slope at 3:1 from where the pad ends, continuing at the same grade below the water line, all the way to the bottom. I told him I wanted the 3:1; my instruction, right or wrong. Rockytopper suggested that I seriously consider re-grading the slope above the waterline, knocking it down to ease maintenance. His words are wise. When I confronted my contractor on the phone with the idea, he waved me off. This page of the Bottomscaping Thread picks up my post with my contractor's explanation.
Your diagram of High/Low pool made me think of it.

If I understand correctly Brettski, the problem would occur if our pond was maintained at the lower level. It seems this could be dealt with by moving the rimmed bank up a little so that it isn't completely hidden by the water.

On the other hand, Alligator's comment made me consider scrapping the rimmed profile altogether and just going with a straight 4:1 all the way. I'm aware of the problems that are eliminated by rimming, but I don't hear people addressing the problems created by it. Brettski, your comment refers to one problem with rimming (safety), and your contractor basically solved the problem by extending the rim all the way up the bank. Is that accurate? Like every solution that strategy has it's own issue which seems to be the maintenance of a steep bank. In addition I doubt that I would enjoy fishing from such a steep bank.

Something I've noticed on traditionally rimmed ponds is that when the water level drops you end up with a very steep bank (the rim) that gets overrun with land weeds. IT seems like it helps prevent (aquatic) weeds when the pond is full, but promotes other weed growth when exposed during low pool situations.

I accept the idea that a gradual slope into the water promotes aquatic weed growth, but it sure does simplify land weed maintenance. Is there any design that eliminates problems with both types of weeds? I'm guessing the answer is no.

What I'm trying to do is avoid a design that is aesthetically pleasing at full pool, but looks stressed in times when full pool can't be maintained due to weather, or even due to design issues. This seems like a common problem with rimmed ponds.

This is where I would really appreciate comments from people who have experience dealing with aquatic plants. I have a notion that by manipulating the water level that I might be able to effect some control over aquatic weeds. If that's true then I will strongly consider a gradual slope into the water so that this pond will look good at any level.

GW,
Both of the two ponds nearest me, stock catfish and tilapia, neither have aquatic weed problems. The difference in levels is about 1 meter, about the distance of water level drop during the hot season.
These ponds are dug from fairly flat ground and the top of the lower level is usually the existing ground level, the higher level is created with the dug out material, set back from the top of the lower level about a meter and about a meter high. No keyway is dug. Many times the inside and top surface of the upper level are covered with a clay/rock mixture which, while ugly, inhibits weed growth and deters erosion. It is easy to walk on and wicks the water to the underlying clay, eliminating almost all of the mud that would be encountered without the clay/rock.
There is only one overflow and that is in the top level.
Of the hundreds of ponds near me, almost none are attractive, looks is not an objective here. There is one pond, about an acre when full, where the owner has taken pains to see the that the ground cover follows the water level. It is some type of low growing grass that requires cutting only once or twice a year. It looks nice and greatly reduces erosion. The water level drops about twice the distance of most ponds and without the grass would look terrible.

The most attractive ponds are usually the naturally occurring ones that have few if any fish. The weeds/plants grow along the banks and follow the water level, few of these ponds become overgrown, since we get quite a bit of rain the weeds/plants are almost always green.

An aside, one of my neighbors has ducks and geese and no herons.

GW, following photos illustrates the way we handled a �pond within a pond.

Not conceived nor planned on an engineering basis, but by necessity to control massive cattail invasion created by leaving a �shelf� on the upper end, perhaps similar to your design.

When pond was at full level, the �shelf� area was 3 ft deep.
As the water receded, cattails spread with the lowering water level
I�m sure with an aggressive and expensive approach for control of weeds and cattails with liners/ rimed banks, etc, the problem could have been solved.

We decided to bring in a dozer to remove the cattails and a track hoe create a �dugout� pond that would be a part of main pond at high water, and a separate 5 ft deep pond in drought conditions.

It has worked well in spite of steep eroded banks due to numerous spring �flash flooding�, and so far cattails are well controlled.
Banks are too steep to mow � will fence within goat pasture for weed control
We could have installed a siphon but elected go with berm/levee instead.

Before.. Cattails on �shelf �area.

Thanks George.

I take that to mean you would always rim a pond.

I would still like to quantify how effective rimming is at discouraging weeds like cattails.

It sounds like you're not completely happy with the maintenance of the terrestrial weeds. I like goats, but I don't think it's practical to fence this entire pond.

Has anyone in the South had un-rimmed ponds and no problems with cattails?

Has anyone with rimmed banks had problems with cattails?

edit: Getting back to my original contour design; If I hold water at the high level and I develop cattail problems on the gradual slopes, will the cattails survive a rapid 3 foot drop in water level? Do they begin in water less than 2 feet deep, and if so, how would they do if they were suddenly 1 foot or more above the adjusted water level?

After a long delay construction starts on Cindy's 7 acre pond tomorrow. Previously I had been thinking of using 2 siphons for the 2 levels, but now I'm not sure. One factor is that the builder will have to install a simple drain through the bottom of the dam due to a constant (and welcome) trickle of water. Of course he'll have to leave the drain and cap it off so I was wondering about using that drain for the lower water level.

Does this make any sense?

Diagram looks workable. Are you going to put in a valve (or a cap that could be removed) at the lowest level of the through pipe that could be used to drain the whole pond if ever needed?

Thanks Theo.

I was picturing a tee fitting were I drew a 90 on the lower drain, with a cap (threaded?) on the upright pipe and a valve on the horizontal pipe.

As a side note, does anyone else worry about having an unguarded valve that could totally drain your pond? I know it would take many days to drain a 7 acre pond, but still, water is precious. It's not that I have any enemies that I know of but I can't help imagining some kids finding the valve and "playing" with it. For as often as you would drain a pond would it be wiser to put a permanent cap and cut it off if you need to drain?

edit: I modified the drawing.

Here's what I'm thinking for the lower drain. Any suggestions for cheaper/better?

Hi GW,
At the risk of killing your thread I'm going to post.
The guy that dug my pond (before I bought the property), basically did what you are considering. My pond was dug to be 15 ft at the deepest point, at full pool. It's not reached this due to watershed etc.. but holds at 6-7 feet with normal rains. In the beginning I cursed the guy, but now I see his reasoning. The average area is surrounded by a shelf that is at a grade that is comfortable to maintain. My wife is able to mow it with our riding mower and can get right to the waterline. The shelf runs on average a foot or two into the normal waterline, after that the slope is probably 3:1. We don't really have any issues with weeds at the waterline as long as we do normal care. We get a few cattails on a small island that will appear at lower water levels but they seem to disappear as the level goes back up. I believe some of this has to do with the Koi my wife put in; we had more cattails before them. The only pain is the dam itself. The face is pretty much a vertical and a bear to keep up. The backside isn't much better, but I've managed to establish a ground cover on it.

I'm not sure if any of this is a help, or if I'm correct in my understanding of your plan. Below is an aerial shot of our pond at a very low point. The blue line is normal pool, and the red one is what I hope we can get to eventually.


-Tim

Good post, thanks Tim. Cindy's pond builder wants to put the lower level at 5 ft. below full pool. He's a conservative type and I think he's concerned about maintaining enough water. Similar to your situation I think. I was thinking 3 ft below full so maybe we'll settle on 4 ft. Or maybe I'll just be smart and listen to him.

One difference is that we're going to go for the most gradual slope we can on the face of the dam. It will depend on how much material we have because the dam is very long. I designed the dam opposite of most people I think, with the back side having a very steep slope that I'll let go wild except for any trees that sprout up.