pond depth

[fudge]

hi all,
new to the site, so here's my first question:, Im thinking of building a nature pond and im wondering what is the right depth for a pond of this type so the creatures can survive if we continue to have bad winters and the pond freezes?. Im not to worried if i have to go deeper than needed as my garden has very sandy soil and is easy to dig.
cheers

[Deb London]

I may be stoned for saying this () but recent research suggests you only need 30 cm (but always add a little more as ponds are not always full at the point of freezing). I would go so far as to say as digging deeper may be bad for winter survival rates. Something to do with photosynthesis vs depth possibly. Large but shallow ponds seem to be the best.

I'd redesigned mine so it was about 90 cm deep (70 - 80 cm in reality) just before this research came to light. However, I had no fatalities (I know because I emptied it late spring). I have Water Soldier that drops to the bottom as the temperature drops, and I wonder if it adds oxygen to the depths. I really don't know if this is the case.

[nightshade]

I think that a minimum of 60cm (2feet) is recommended with shallower areas.
If I was digging my pond again I would go for a full metre deepwith shallower areas of 30cm (1 foot) and 60cm (2feet) to accomodate planting.

[Deb London]

I thought I'd better add the reference.

http://www.pondconservation.org.uk/R...%20Summary.pdf

[King Edward]

How large (area) are you planning to make your pond? One of the problems with digging too deep is that it's then difficult to have enough shallow areas, especially really shallow areas less than a few inches deep, without then having really steep drops. Especially if it's a small pond, I can't see the value in having a sort of deep pit in the middle.

If you're going to plant in conventional baskets then obviously you need to dig deeper to accommodate these, which in itself can make the shallow areas too deep. For that reason alone I'd go for planting directly into a sand layer on the bottom.

This is also worth reading: How to make a really good wildlife pond (3): the pictures The Garden Pond Blog (and related articles on the same blog).

Regarding freezing, even a small shallow pond is unlikely to freeze more than an inch or two on top. For example, this advice from Pond Conservation (link):

1. Ponds shouldn’t be too deep for their area. Shallow ponds – less than 30 cm (1 foot) are more likely to have higher oxygen levels in the water which helps amphibians, so a good pond shape is wide and shallow – a saucer rather than a tank.

This is the exact opposite of much of the standard advice, which says that ponds ‘should be deep to protect them from freezing solid’. In fact, we know that most ponds didn’t have more than more than a few centimeters of ice, even during the very coldest days of the 2009-10 winter – so ‘freezing solid’ isn’t the problem.

2. A large build-up of leaves and sediment on the pond bottom is probably not good news – almost certainly because this de-oxygenates water. This is especially a problem in ponds which are small and deep.

I'm currently in the process of constructing this pond at home, which is about 55 sq metres with a max depth of about 14". Most of it's shallower though, with varying depths - I'll try to get a photo showing this better. Planting will be in a thin sand layer, especially in the shallows.


The small pond is currently full of tadpoles, hence the cover to keep off ducks.

[tom00_uk]

mines over 4ft in the deepest, but thats because were on light loam so it took very little effort to dig out.

but the recent addition is no more than 1.5ft, as there were a lot of tree roots in the area so i worked with what i had available. Though it has allowed me to have a pool, riffle and a run mix over the pond

never had any winter die off's of large life like amphibians or fish that i have noticed

[Jackaroo]

They do say that a good depth of pond allied with a good oxygenating plant(A living plant that is) and with a sensible proportion to surface area lessens the likelihood of green water! I'm sceptical myself but that's what they say.

[Kayleigh]

Originally Posted by Jackaroo

They do say that a good depth of pond allied with a good oxygenating plant(A living plant that is) and with a sensible proportion to surface area lessens the likelihood of green water! I'm sceptical myself but that's what they say.

Yes its true as the water dont warm up as much as a shallow pond would so reduces the chance of algae bloom..

[King Edward]

You don't need shallow water to get algal problems. My grandfather's pond is uniformly about 2' deep except for some relatively small shelves about 1' deep, but had large amounts of blanketweed last summer (and starting again now). This is much more of a water quality issue, not to do with the depth.

Besides, warm shallow water is desirable for wildlife and is not something to be avoided.

[dampflippers]

I would (and have) queried the Big Thaw results.
My hypothesis would be that shallower ponds of 30cm depth were not deep enough to be chosen by frogs to hibernate in and therefore did not have as many deaths in them.

I would suggest 18 to 24 inches.
12 inches to me would suffer too much from drought reduction in depth and drying out.
And if you choose to plant waterlilys (not native obviously) this isn't deep enough.