Pondless stream max depth??

[Dregae]

I am in need of some advice about the maximum depth for pondless streams. We are planning to put a waterfall and stream into our duck aviary(mandarins) and would like a section of it to be fairly deep. Ideally 12-18 inches deep with a shallow beach area opposite it to allow the babies to get in and out easily. Then another section of it be about 9 inches deep. The stream we are planning is approx. 25 feet long but at its widest it's only 3.5 feet wide the rest of it averages 1 foot. I searched all over but couldn't really find an answer on the do's and donts for the depths of pondless waterfalls. While I'm here asking questions (and no doubt sounding very silly) what size reservoir would I need. The area we have for the reservoir is not large but the ground is good and we can dig down further very easily. Thank you all for any advice!!!!

Grace

i have included a rough layout of the stream we have in mind. Each square is one foot. The area of the stream with the hash marks is where it would be the deepest. Hopefully it's clear as mud.

 

[Lisak1]

You want a reservoir big enough to hold the entire volume of your water feature. That way if the pump stops for any reason the water can all drain into the reservoir without flooding you out. If you have areas that will hold water in your stream, you can subtract that from your total volume.

If you fill your reservoir with matrix blocks (look up Aquablox for one example) you can hold a greater volume of water in a smaller space than if up I filled he'd tire basin with rock or gravel.

Ask any questions you might have - we have a small pondless waterfall in our yard and love it!

 

[Meyer Jordan]

You don't indicate what you would like in stream velocity. You also don't mention the elevation changes within the streams course. Will there be cascades along the course of the stream?

 

[Dregae]

The waterfall starts in the upper right hand corner of the drawing. The initial height is around 3.5-4 feet and in the space to the first line drawn across the stream it will drop 2 feet. Each line drawn across the stream is an elevation change and then the last long narrow section is just a series of Rapids or short elevation changes to the reservoir. I wasn't sure how to draw that in more clearly so I hope I explained it ok?!?!

 

[Meyer Jordan]

What will be the total elevation change from the waterfall plunge pool to the reservoir?

 

[Dregae]

Approx four feet.

 

[Meyer Jordan]

One last question. How large is the area available for the reservoir?

 

[Dregae]

We have around 3x4 feet. If the matrix boxes need more space we can extend it to 3x5 and we could go very deep. The ground is very good and there aren't any tree roots to worry about.

 

[Dregae]

Another question I forgot to ask is what kind of pump is needed?

 

[Dregae]

The other option with the reservoir area is to extend it up under the stream. I've heard of people doing that but I don't know much about it

 

[Meyer Jordan]

Given the stream specs that you listed in your opening post, you will have an estimated (liberally) 350 gallons of transit water. Allowing for an appropriate reserve, the reservoir should ideally be able to accommodate 500 gallons. This means that with a surface area of 3 x 5 (15 sq/ft) the reservoir will need to be 4.5 feet deep.
You have not mentioned including any biofiltration for this project. Some level of filtration will certainly be needed given the presence of ducks otherwise the reservoir will soon turn into a very smelly cistern.
Yes the reservoir can easily be located under the lower section of stream.
Most pondless projects utilize a submerged solids-handling pump.

 

[Dregae]

I defiantly want filtration!! I was looking at aquascape and the helix bio falls I just hasn't decided yet. I like the helix a lot but it's more pricy.

So it's okay if part of the stream is 18" deep?

Thank you for helping figure out the reservoir as well!!

 

[Dregae]

When figuring out the size of the reservoir could you subtract the water that would stay in sections of the stream if the pump was shut off. I figure I would have roughly 100 gallons give or take that would not flow back into the reservoir when the pump was shut off.

Also has anyone used milk crates in the place of matrix cubes in such a large reservoir. There is a site that sells milk crates cheap and figuring that each crate would hold 10 gallons I would need about 40-50 they would be half the cost of matrix blocks.

 

[Meyer Jordan]

Easy Pro also manufactures biofalls. They may be more reasonably priced.
The question is- How many ducks are in your aviary?

An 18" depth is really OK for the section of stream that it will be in. This will actually be the plunge pool for the waterfall and needs to have some depth to minimize splashing.
One other thing that needs to be considered is the walls of the reservoir. Soil wall of that depth will require stabilizing to avert collapse. The only way to do this is with poured concrete or reinforced concrete block construction. Either way will reduce the capacity of the reservoir so extending the reservoir underneath a portion of the stream may be the best route to take. That way you may be able to reduce the depth to only a couple of feet which should not require any reinforcing.

 

[Meyer Jordan]

When figuring out the size of the reservoir could you subtract the water that would stay in sections of the stream if the pump was shut off. I figure I would have roughly 100 gallons give or take that would not flow back into the reservoir when the pump was shut off.

Also has anyone used milk crates in the place of matrix cubes in such a large reservoir. There is a site that sells milk crates cheap and figuring that each crate would hold 10 gallons I would need about 40-50 they would be half the cost of matrix blocks.

Milk crates will serve the purpose. I have used them before.

I would recommend keeping the reservoir capacity at 500 gallons, just for the added cushion.
You also need to plan on some form of pump vault either manufactured or DIY. You need access to the pump.