pond ideas ?

Hello Permies,

I'm planning to dig a small pond (area of about 15 square meters), and I'm pondering different design options. I'd be grateful for advice on a couple of issues.

I'd like to make the pond without an artificial liner, but I have yet to dig a test hole to see what the soil looks like deeper down. I expect it to be a mix of sand and clay - hopefully more clay as I dig deeper down.

The pond has to be small because (a) available space is limited; (b) I'd like the pond water to have proportionately more depth than surface area; (c) the pond will be fed by rainwater from the house roof and rains will be infrequent in summer so an oversized pond will be difficult to keep filled in some parts of the year.

The pond will be situated on a gentle slope, downhill from the house, but quite close to it (about 6-8 metres, or 18-24 feet, from the house).

My questions at the moment are:

- any issues due to the proximity to the house?
- what depth (at the deepest point) would be recommended for a pond of this size (surface) ? Maximum? Minimum?
- should i build ledges into the sides? Or leave them smoothly sloping? And what would be the ideal angle of the sides ?
- some sources recommend compactiing the clay that lines the pond, without mentioning "puddling". Other sources talk about puddling as a means for increasing water retention, and say nothing about compaction. What's the right approach?

I'll look forward to your replies !

Levente

Unless you've got really good clay content....like water stands by itself overnight in your test hole, sealing your pond without a liner is going to be a huge, iffy project. Even with good clay content you've got to compact the clay, something ordinarily done with the weight of heavy machinery on larger ponds. Look up bentonite and gley.
You can make the pond deeper, relative to the size, if you use a liner, since the water will push against the liner and hold the banks at a steeper angle. Without a liner you will have to figure out the angle of repose for the material...usually no steeper than 2:1 (run:rise). The carpet-sandwich technique would enable you to line a pond of this size pretty cheaply, and probably more quickly than any non-liner technique, especially without heavy machinery....

Levente,

In the design of a pond down slope from my house that was to be deeper than it is wide -- there came up a number of issues similar to what Alder brings up.

For instance, as he mentioned with slope of banks. If you have a deep pond with near vertical sides, then use a liner, being down hill you can have issue with runoff getting behind the liner. Depending on the type of soil you may need to step pond down to depth, or reinforce walls.

Water just can't run down a hill into the pond. It will need to be collected then drained from a higher elevation via pipe to prevent seepage near structure. Using it to hold rainwater from roof you'll want to run drains all the way to pond area (or collect into a sump then via larger pipe to pond.)

You may want to have someone who builds koi ponds, or does in-ground vinyl swimming pools to come out with some estimates. You could end up with a nasty mess, or larger erosion issues if you just dig a hole. It may have too much water some seasons, very little water in others.

If you're going to use the pond for fish you may not want roof runoff in your pond without first going through a marsh or retention pond. Be more specific about what you want this pond to do, look at existing designs. Pond usage has huge impact on design.

For my project I'm going to need to revisit a lot of things and have moved it down my priority list because of some serious safety issues you can face with a deep pond.

Sincerely,

Justin

any pond needs a gentle slope on one side for critters that fall in ..to be able to climb out...but anything shallower than a few feet deep will fill up quickly with cattails and weeds if there is seed in your area..so deeper better..

i agree with the mentions above..smaller ponds tend to not really hold much water..unless they have been compacted or lined..due to evaporation and leakage.

you can visit my blog (below) and check out the pond I have..it is much larger than you are describing, and the shallow areas are all filled with plants..all brought in by nature except the water lilies.

ledges are great for planting plants..and do help give a foothold to critters.

Alder Burns wrote:Unless you've got really good clay content....like water stands by itself overnight in your test hole, sealing your pond without a liner is going to be a huge, iffy project. Even with good clay content you've got to compact the clay, something ordinarily done with the weight of heavy machinery on larger ponds. Look up bentonite and gley.
You can make the pond deeper, relative to the size, if you use a liner, since the water will push against the liner and hold the banks at a steeper angle. Without a liner you will have to figure out the angle of repose for the material...usually no steeper than 2:1 (run:rise). The carpet-sandwich technique would enable you to line a pond of this size pretty cheaply, and probably more quickly than any non-liner technique, especially without heavy machinery....

Hi Alder,

Many thanks for the advice.

The idea is to make a pond that's as "natural" as possible, I wouldn't mind if it allowed just a tiny bit of seepage.

This pond http://www.forestgardentransylvania.org/PHOTO-ALBUMS.html is not very far from my place (=similar soil type), and smallish, though probably about 3 times larger than what I'm planning. It's made without a liner, but then it was excavated & compacted with heavy machinery... If I recall correctly, it's about 2m (6ft) deep. I visited the place in September after a severe 4-month drought, and the pond was still more than half full.

On the other hand, in this example that I found recently the small pond is also hand dug and apparently without a synthetic liner. Of course the video doesn't show how long the pond will hold the water or what problems (if any) it will cause in the long term...

I've made a note of your advice regarding the angle of the banks.

I'll keep researching and pondering various options. My intention was to design some type of water feature that makes use of runoff, melting snow, and the overflow from the rainwater cisterns.

It may be that I'll end up with a (rather shallow) vernal / seasonal pond...

Best wishes
Levente

Justin Hitt wrote:Levente,

In the design of a pond down slope from my house that was to be deeper than it is wide -- there came up a number of issues similar to what Alder brings up.

For instance, as he mentioned with slope of banks. If you have a deep pond with near vertical sides, then use a liner, being down hill you can have issue with runoff getting behind the liner. Depending on the type of soil you may need to step pond down to depth, or reinforce walls.

Water just can't run down a hill into the pond. It will need to be collected then drained from a higher elevation via pipe to prevent seepage near structure. Using it to hold rainwater from roof you'll want to run drains all the way to pond area (or collect into a sump then via larger pipe to pond.)

You may want to have someone who builds koi ponds, or does in-ground vinyl swimming pools to come out with some estimates. You could end up with a nasty mess, or larger erosion issues if you just dig a hole. It may have too much water some seasons, very little water in others.

If you're going to use the pond for fish you may not want roof runoff in your pond without first going through a marsh or retention pond. Be more specific about what you want this pond to do, look at existing designs. Pond usage has huge impact on design.

For my project I'm going to need to revisit a lot of things and have moved it down my priority list because of some serious safety issues you can face with a deep pond.

Sincerely,

Justin

Hi Justin,

Thank you for your contribution, much appreciated !

I don't intend to grow fish in the pond, or at least not until I've learned its "habits" and can be sure it's behaving well. As I wrote in my reply to Alder, I'd just like a water feature - possible even a seasonal pond / wetland, which may fill up every winter / spring, and be almost dry by say August. I guess I could live with that - although of course a "real" permanent pond would be even nicer

And yes indeed, the rain water would arrive into the pond via pipes from a sump - that's been the plan.

You mention reinforced walls - can you suggest any specific techniques? I'm strongly in favour of methods that don't involve synthetic materials

Best
Levente

Brenda Groth wrote:any pond needs a gentle slope on one side for critters that fall in ..to be able to climb out...but anything shallower than a few feet deep will fill up quickly with cattails and weeds if there is seed in your area..so deeper better..

i agree with the mentions above..smaller ponds tend to not really hold much water..unless they have been compacted or lined..due to evaporation and leakage.

you can visit my blog (below) and check out the pond I have..it is much larger than you are describing, and the shallow areas are all filled with plants..all brought in by nature except the water lilies.

ledges are great for planting plants..and do help give a foothold to critters.

Thank you, Brenda

I'll keep your advice in mind

Levente

Levente,

Levente Andras wrote:You mention reinforced walls - can you suggest any specific techniques? I'm strongly in favour of methods that don't involve synthetic materials

My original design had six foot retaining walls of stone or cinder (those blocks that stack on each other leaning slightly back into the hill.) However, if someone ever fell into that pond they wouldn't be able to get out easily. Some will reinforce small ponds by building a frame of treated wood or railroad ties. I primarily was looking to do a rectangular reflecting pond that held a lot of volume for fish.

Best way is to do like is being shown in pictures you reference where they step down into the pond. This is easier with a larger pond because you can have larger steps. Last two ponds I help dig were ornamental (only 8' long, about 6' wide kidney) with several steps down to deep center, used a liner and placed rocks around inside of steps.

Without a liner those steps in larger ponds will wear down like they have in a detention pond I help manage -- the retaining walls help maintain structure around critical points. Steps also keep sides from washing down in deeper ponds, gives you a place to plant, and offers different habitats. Of course, if you're just looking for a seasonal pond, you just dig a low swale that turns back around on itself.

At 15 square meters (mentioned in your original post) you may not be able to get more than a meter deep in the middle without some kind of support for the walls, unless you line the pond. A formula I see for larger ponds is 2n for every n in depth, where n is step height. There are burlap bags designed for rebuilding retention ponds that might work until your pond is established.

In proofing my plans I also found that ponds near a house need to be sealed -- i.e. won't create a water table high enough to change soil structure, leak into basement, or run under the foundation. It's likely that I'll end up with a pond further from the house damning off a low area with a liner. You face a lot of risks having a larger body of water near your house.

Even if you just dig an earthworks or catchment swale, take some pictures. Sounds like an interesting project.

Best,

Justin

Thanks Justin,

Some really good ideas.

Perhaps ledges and retaining walls are the way to go in this case

I still wonder how far from the house would be safe to site a small pond... I would have thought 8...10 m downhill to be ok, but some may think that's too close

Best
L_

That would depend greatly on your soil characteristics. Very well-drained soil and a low/distant water table make the issue almost moot; clay and a high water table would mean that you must be very careful. I would certainly not have a pond higher than the basement floor, and several feet lower would be better.