Colin (see the comments) has posted a great set of pictures of progress with his new pond.
I’m going to feature a few of them here but just to start with I thought it would be nice to use this classic frog picture because it’s such a great photo.
The picture will load a bit more slowly than usual to get a good resolution.
Click to see the bigger picture
On Sunday we visited a big, famous, house which has a nicely laid-out garden.
But oh dear – those ponds.
If I had to look out on ponds like these every day I think I would shoot myself!
Still it’s probably convenient for the Duke of …………………… that I’m happy with a modest suburban garden that has three really interesting ponds in it, rather than wanting to live in a world famous cultural site where the water is about as interesting as the car park.
But I did like the house, though perhaps it’s a little on the unnecessarily large size for one family.
Getting a good natural edge to a wildlife pond is still one of the most difficult parts of the pond construction process – mainly because we don’t yet have much experience of how to do it.
Stone or slab edging is very much easier.
So it was no surprise to get this cry for help from Janet. I had much the same problems making the ‘New Pond’ last year.
So here’s her mail:
‘Hello,
I am currently constructing a wildlife pond and have been following your advice (on internet and in the RHS magazine etc).
However, I was planning to have flat stones round the edge of the pond, not grass. (This will hold down the liner with some hard core and sand.)
I cannot understand how putting the turves back on top of liner will allow the grass to grow. Am I missing something?
And I also thought that by putting turves at the edge, there was a danger of soil slipping into the pond which causes problems.
The pond is one and a half metres across, is circular, is in the lawn, in a sunny spot, and is not too deep. (About 12 inches plus I think.)
Thank you for all your help on the website and in articles.
Janet’
Putting tuves back on top of a liner sounds like it won’t work and the grass will die.
Actually as long as you leave a little soil and roots the grass will grow on top of the liner – it will probably go yellow for a while, unless the weather is very wet, but it will recover and grow on top of the plastic.
After I cut the turves to edge the New Pond I knocked off most of the soil just leaving the mass of grass roots and a bit of soil – doing this is probably enough to keep too much soil from falling in the pond. The turves end up about 1 ½ to 2 inches thick.
Pond edge design - click to enlarge
Here are before and after photos of the New Pond edge turves. It works pretty well.
Here are the turves cut and ready to lay on the liner once it is in place. You can just about make out the low bank of soil in places that stops the water running back into the pond.
Next you can see the turves laid on top of the liner – the finished job.
Both these pictures were taken in April 2009 when the pond was made.
The ‘after’ picture below is from 4 Jan 2010 – the turves are growing well and holding down the liner.
So for the edge of the pond we’ve worked out a reasonable solution.
But inside the pond is still a bit of a mess – we haven’t rushed to cover it in plants (one way of hiding the liner) but we haven’t quite yet worked out a good way to get sand and gravel to stay in place on the gently sloping smooth butyl. Of course this isn’t a problem when you dig into natural clay, sand or gravel – but it’s a key issue with a synthetic liner: how to get a natural substrate anywhere except where the liner is absolutely level.
Any ideas much appreciated!
Spot the diving beetle (click for a closer view)
Diana has sent me a picture of one of her great diving beetle larvae hanging in its distinctive pose below the water surface of her pond – waiting for passing frogs!
The picture set me to wondering which of our six Great Diving Beetle species Diana had.
The commonest are the, well, Common Great Diving Beetle (Dytiscus marginalis) and the Black-bellied Great Diving Beetle (Dytiscus semisulcatus).
It’s probably less likely to be one of the four other species – the Lapland, Divided, Yellow-bellied and Green Great Diving Beetles, respectively Dytiscus lapponicus, D. dimidiatus, D. circumcinctus and D. circumflexus – as they usually have more specialised habitat requirements – but who knows?. (By the way, I’ve more or less made up those English names just now! – except Black-bellied and Common which are already in use).
There are close ups of several of the six species on the excellent Biopix site:
Black-bellied Great Diving Beetle
Divided Great Diving Beetle
Yellow-bellied Great Diving Beetle
In a very short e-mail Jim has managed to pack in a lot of pertinent questions! I thought the answer might be of more general interest.
Pity I couldn’t make the answer as short and pithy as the questions – must be a lesson in there somewhere.
Anyway….Jim says
‘A colleague at work forwarded on the results of the Big Pond Thaw survey 2010 and I was very interested in your advice to have shallow ponds (<30cm), as they have higher levels of oxygen. I thought that shallow water depths tended to be warmer (and certainly more prone to warming) than deeper water and therefore potentially less oxygenated as colder water retains oxygen much better? This lower oxygenation would therefore be bad for the amphibians. In addition, I’ve been helping out with toad migrations in our local area and I was informed that toads prefer deep water and therefore are less likely to breed in shallow (<60cm deep) ponds? Would a pond with a graded depth be the best compromise?’
Dear Jim
You’re right that cold water has more oxygen than warm water, all other things being equal. Theoretically, 100% saturated oxygen concentrations go from about 15 milligrammes of oxygen in each litre of water at 0 C down to about 8 milligrammes per litre at 30 C.
So, in theory, half as much oxygen in really warm water as in cold.
But lots of other factors can affect this.
If there are a lot of plants and algae producing oxygen you can get significantly more oxygen in the water than ’100% saturation’, and if there’s lots of decaying organic matter, or lots of fish in a small pond, oxygen levels can go down a lot as bacteria and animals use up oxygen. And I expect you’ll be familiar with the idea of summer oxygen swings during algal blooms – the algae produce oxygen like mad in the sun, then use it up during the night.
So to answer your questions specifically:
The first thing to say about shallow ponds is they don’t automatically have more oxygen than deeper ponds. A shallow pond full of leaves will have low oxygen levels because of all the rotting organic matter. But they do have a better chance of generating a lot of oxygen internally if they’ve got plenty of plants (or for that matter algae) because they’re completely in the light.
Plants are a crucial part of the story here because they can completely alter the amount of oxygen in the pond – at least where there aren’t large quantities of organic matter.
Next, you’re right of course that shallow water is warmer and warms up more – but this is natural, not bad.
In fact its one of the plus points of very shallow water – its wonderfully warm. And being well-lit it can also be well-oxygenated.
Also many pond animals – beetles, backswimmers and boatmen, many snails, rat-tailed maggots etc etc – come to the surface to breathe air and others have adaptations to lower oxygen levels. The ‘warm water bad/cold water good’ idea is really something from fish keeping – where warm water does make it more difficult to keep fish, especially ornamental fish, because they will usually be stocked at a very high density and so be under considerable oxygen stress as water warms up.
And finally of course you’re right about toads generally being associated with bigger (and so usually deeper) ponds. But quite why they are is, I think, still a bit of a mystery. The tadpoles do tolerate fish predation so that would make them favour these situations (big ponds are more likely to have fish) but they do also breed in small garden ponds – much less so than frogs of course, but they do, so the pure size of the pond is obviously not a limiting factor.
In our detailed surveys in Abingdon of garden ponds, off the top of my head, 2 out of 30 had breeding toads compared to about 20 out of 30 with breeding frogs. And thinking about it, they’re abundant in one of the most wonderful ponds we know in the New Forest – a famous spot for all sort of extremely endangered freshwater plants and animals – and here you see toad tadpoles swimming about in a few inches of water, and the whole pond barely comes up to your knees.
I think I’ve heard that toad tadpoles also have higher oxygen requirements than common frogs which, given that larger ponds and lakes would often have higher and more stable oxygen levels than smaller ponds, might also be part of the explanation.
More generally, I’m not sure the oxygenation is all that critical for amphibians – of course the tadpoles/newtpoles need oxygen but the ones that live in ponds are probably adapted to the natural levels, and fluctuations, of oxygen that you see in good quality well-vegetated ponds. This is different to rivers and streams where the ‘typical’ animals are those that need oxygen to be constantly high, the natural condition for rivers because of the water movement.
Finally, as you’ll probably have seen for yourself – frog tadpoles love the almost hot water you get at the edge of really shallow ponds and swarm there.
So, to try to wrap all that up – our very shallow ponds at home produce a lot of oxygen, including in cold weather, because they have abundant plant growth (including mosses which are winter green); the small volume means the oxygen can re-charge quickly, and in warm weather there’s so much photosynthesis going on that there’s plenty of oxygen production.
Although we have plenty of leaves in my ‘Old Pond’ we like leaves, and in a shallow pond they don’t seem to use up much oxygen. In deeper (down to 50-60 cm ponds) with lots of leaves there is so much organic material that you’re creating a big oxygen stress – and the lowest oxygen levels in the Abingdon ponds are all very leafy ponds.
Finally our measurements in Abingdon garden ponds showed that there was never more than a degree or so difference in the temperature between the top and bottom of a garden pond – they’re too shallow for the depth to make any difference. The idea that deep water has more oxygen comes from studies of lakes where this, of course, is true and there’s a big enough mass of water for there really to be separate areas of water in the same waterbody – this doesn’t really happen in small ponds.
Last – the 64,000 dollar question – should we have graded depths? I’m not sure that makes all that much difference in small ponds. I think our ponds suggest that shallow works fine; going down to half a metre, or a metre, in a garden-pond-sized pond is going to give steep sides.
In practice, if you can fill a deep steep-sided pond with scrupulously unpolluted water, it’ll be fine – it’ll be great as a habitat but it won’t be quite as good as the pond that also has very gently sloping sides and plenty of shallows. To achieve that in the relatively small space of a garden, usually mean having shallower ponds – although as we’ve still so much to learn about designing small ponds for wildlife people will probably be able to thank up other solutions to the problem.
I think one of the best things about all this is just how much there still is to learn about something apparently so familiar as the garden pond.
Pond 3: Katy's Pond (you can see the 'Old Pond' in the background and the 'New Pond' is to the left, out of view)
What’s the right time to make a new pond?
The simple answer is: anytime!
And that’s what we did last weekend.
It’s called Katy’s pond, and is pond number three in our garden. So now we have a ‘pond complex’.
A pond complex is simply a group of ponds, fairly close together, which provide a wider variety of habitat than a similar area of water in one pond would.
In the countryside we recommend always making groups of ponds rather than single ponds – and there’s no reason why the same thing shouldn’t be true in the garden.
It’s rather what the most natural wetlands are like – with groups of waterbodies close together of different sizes, shapes, depths and degrees of permanence – separated by patches of dry land.
It's a small hole - digging only took a couple of hours - here I am cutting under the turf so we can tuck the liner in
We used some offcuts of liner for an underlay
Katy trimmed the underlay
We laid the liner in place
Then we filled the pond
And in one afternoon the whole thing was finished.
The next day: Katy's not quite as gloomy about it as she looks! Actually on Monday she went straight into the garden when she got home from school to see how the pond was getting on.
Katy’s pond is our smallest (1 m x 2 m) and shallowest so far: with a maximum depth of about 10 cm it’s safe for all but the very youngest children. It’ll be interesting to see how it develops compared to our bigger ponds.
We put it in an afternoon (though we did have the basic outline of the hole dug already).
I’m envious!
Diana (see the comments) was inundated with great diving beetles last year.
So far this is one thing we haven’t seen in our ponds – I’m rather hoping that, with 100,000 tadpoles on the way, we might attract a few beetles to the feast this year!
So far on offer for hungry tadpoles (see the comments) we have:
- boiled lettuce (sounds yuk)
- rabbit food! (urggghh)
- nice water plants (well, at least the algae living on them)
- very thin slices of courgette (very Nigella)
- melon slices (mmmmmm, things are looking up).
Any more suggestions?
-
This site in the Derbyshire Peak Distict experienced one of the worst frog mortalities at the end of the cold winter weather with at least 150 dead animals retrieved. (Photo: Roger Naylor)
We will be announcing the results of the Big Pond Thaw survey today.
We will send a summary of the report to everyone who participated (where we have an e-mail contact address) – if you don’t receive a copy, and would like to know more about the results, check the Pond Conservation website, or look at the blog later.
And thanks especially to everyone who sent us information about their ponds: it’s provided some unique new insights into what makes ponds tick.
UPDATED: Click here to download the summary of the report.
Common Duckweed (Lemna minor) in frogspawn in my old pond today
There’s no duckweed in my old pond – well, until I noticed some yesterday.
Nothing unusual here you might think. Duckweed colonises pond – it’s not exactly news.
But actually there was something unusual about this, as the picture above shows.
It’s associated with the frogspawn – just a few fronds (I counted about 10 altogether) dotted around in the big mat of spawn, and nowhere else.
Why just there? It certainly wasn’t in that part of the pond a few days ago, before the frogs came, or in any other part of the pond (I know: I’ve been watching out for it like a hawk, or perhaps that should be like a duck).
There was definitely none last year.
Although I’ve no way of proving it, it rather looks as though the frogs may have brought it in.
