Clearing the curly leaf weed

This is a close up of potamogeton crispus, the curly leaf pondweed. The tiny bud-like protuberances are flowers, which just stick up above the surface and produce a surprising amount of pollen when rubbed.

And below is a large pile of it, produced by cutting low down with a sickle, letting it float to the surface and then using a large grass rake to pull great masses of it to the side, where it can be thrown by hand on to the bank. Waders were worn, of course.

It had taken over a third of the area of the pond and in this phase I cleared about one third of it in two hours. It reproduces mainly by something called a turion which is bud-like and distinct from a tuber. The turions lie dormant on the bottom through the winter and are more important in its reproduction and spread than seeds. (Apparently asparagus grows from turions as well). So next winter I’ll try raking out the most affected places in the pond to reduce next year’s growth.

I read on the web that it grows early in the season and very fast, so tends to dominate the pond early and restrict other plants. But in July it dies back, and if there is a lot of it then the rotting vegetation can deoxygenate the pond. The Royal Horticultural Society advises cutting with a scythe in the summer and composting. I’m now looking for an old scythe because Christine’s is far too good to use under water.

The good news is that so far there is very little blanket weed so maybe the curly leaf pondweed is squeezing it out. Let’s hope so. It is a lot easier to clear.

Curly pondweed

After 5 years of dealing successfully with blanket and duck weed, a new challenge, potamogeton crispus, otherwise known as curly pondweed. A few plants appeared last year and the year before. This spring there are very large growths.

It is listed by the Royal Horticultural Society as troublesome and the advice us simply to pull it out to reduce the growth, though once in a pond it won’t disappear altogether. So when the water is a bit warmer, it will be waders on and into the pond to do some weeding. It is noticeable that the areas where I raked the bottom last November to clear debris there is almost none of the new weed, so that is another longer-term option.

The good news is that it’s quite easy to pull up and it also seems to blanket out blanket weed. Curly pondweed is sold as an oxygenator for small ponds and aquariums and only becomes a real nuisance in large ponds and lakes. Oxygenation is a plus, too.

How it got into the pond is unknown.  Our neighbours did have carp in a tank which they transferred to their pond, which connects with ours, so that is a possibility.

Five year clear out

It has been 5 years since we cleaned out the pond, and silt from autumn leaves is building up. Time for a clear out, and these are the tools:

 A wide plastic toothed rake for the pond bottom and a grass rake for shovelling out the debris.

They say the mud in a pond deepens by half an inch a year or thereabouts, which is why round here farm ponds are cleared every 50 years or so. As I’ve mentioned before, there’s a school of thought that ponds should be left to mature untouched for the sake of  the wildlife, but I don’t agree. It was astonishing how quickly the flora and fauna returned after completely emptying and desilting in 2011.

I sketched the pond in my notebook, dividing it into 4 sections. I waited till November, well after the  last amphibians have left the pond, put on my waders, and systematically raked the bottom of two of the sections with the big yellow rake shown above, and then made a note on my sketch of which bits I had done. Next year I will rake the remaining two sections. Not having done this exercise before, I thought  I’d wait a season to see what impact the raking was having. I’m not concerned about the invertebrates and amphibians, but I do want to check the effect on blanket weed growth, because I will be stirring up the nutrients that seem to encourage them.

Raking was aimed at pulling large piles of debris to the edge where I then scooped it out with the smaller grass rake onto an old plastic tarpaulin on the bank – important because the slurry otherwise makes such a mess of the grass and plantings. I then used a wheelbarrow – about 20 loads – to distribute the muddy piles of rotten leaves and twigs in the garden.

 As this picture sort of shows, it does dry out into something very like compost. Meanwhile, the bottom of the pond is visible again, rather than a layer of rotting leaves.

Fishy menace

We’ve got a fish problem: our pond is the main part of an old moat, one arm of which is in a neighbour’s garden. The neighbours keep fish, and have put a fine wire mesh across the narrow connecting part at the boundary to keep them on their side. Unfortunately, very young fish got through it and we are now infested with small grey carp of some kind, including goldfish, which appear to be breeding. The amount of insect life in the water seems to have dropped sharply, and suspicion falls on the fish.

There are also three big grass carp which arrived in an earlier escape three years ago, but we rather welcomed them. They are entirely vegetarian and seem to be keeping down invasive weeds including duckweed.

Tackling duckweed menace – again 

After a year with hardly any duckweed (don’t ask me why) it’s back with a vengeance.

 There are 8 ducks apparently hoovering it up for hours every day, but neither they nor the grass carp, which also feed on duckweed, make much difference when there’s this much on the pond. In the right conditions, according to the books, duckweed can double in 3 days.

We clear it by the very simple method of putting on waders, getting into the pond, and pushing a long 6 inch plank held on edge through the water, so the weed piles up in front of it.

image
Enough of the plank is submerged to trap the weed in large quantities.

imageWe push it to the bank and then scoop the thick accumulation of duckweed out with a grass rake, onto a large plastic sheet, allowing the water to drain back into the pond along with lots of tiny creatures. Without the sheet, the grass verge turns into a bog.

imageThe duckweed doesn’t rot easily into compost so rather than put it on our heap we use it as a mulch or put it on poor, clayey ground so that in the long term it will work into the soil.

imageIt takes three or so hours to clear the pond completely by repeating the process.

The work is best done on a day with a gentle breeze that moves the duckweed towards you. Working on the downwind side of the pond, a cleared area appears after each sweep of the plank.

imageThis quickly fills again with wind-blown duckweed.image

The other end of the pond clears as the weed moves downwind.
image

Without wind, the duckweed tends to spread back over the pond again but in a much thinner layer – because there is less of it – which makes sweeping less productive. So if the wind drops, best to take a break till it comes back again. It’s much easier to rest and let the wind bring the weed to you than to chase it round the pond.

Below, the ducks come back to feed on some of what’s left – as a name, duckweed is exactly right.image

This method does of course depend on having a pond you can walk in but many ponds have thick layers of mud that make that very difficult. Ours was like that till we desilted it. So early attempts to clear duckweed used three planks tied loosely together with a rope at the end of each of the two outer planks. With a person each side of the pond holding one of the ropes, the whole apparatus could be pulled  down the pond, sweeping the duckweed along. It worked up to a point, though not nearly as efficiently as getting in with waders.

Either way, the objective is to remove as much as possible of the duckweed so that fish and ducks will control what’s left for the rest of the summer. It is impossible to get rid of all of it. There seems to be a critical area of coverage below which the duckweed grows no faster than than it is consumed by the pond’s inhabitants.

Duckweed survives the winter by changing to a dormant form that sinks to the bottom, rising again the following year. So by removing as much as possible this year, next year’s growth gets off to a slow start.

And below is the pond this week with most of the duckweed cleared. That splash of green near the centre  of the photo is a reflection of a bush in the clear water! Now we just have to keep our fingers crossed that the ducks and the fish eat what’s left around the edges faster than it grows. (PS 20 August: duckweed completely gone).

image

 

Pond safety – fences and small children 

IMG_4377 We’ve been a bit cavalier over pond safety, given that for the last ten years or so we’ve been having visits from families with toddlers. Two sides of the pond are protected by a hedge and our neighbour’s fence, but the other side is open to the garden, apart from two short stretches of dense copse and closely growing trees. Until now, we’ve been reluctant to cut off the pond from the garden because most of the time only adults are here, and we like the free movement.

We have relied on a ramshackle fence made from 3 foot high chicken wire fixed every 6 feet to small round pointed posts. When children come, we unroll the wire and posts, which are stored rolled up behind the compost heap. The posts are permanently stapled to the wire, and we hammer them into the ground round the pond. There’s about 120 feet of it, divided into sections for portability, but it was getting more and more of a hassle to rig it up, especially at short notice.IMG_4382

Now we’ve made a permanent fence round the pond near the house from 4 inch half round sharpened posts beaten into the ground using a club hammer, protecting the tops from splintering with a piece of scrap wood. There is a single 3 inch half round rail running near the top of each and the gaps between posts are filled with one inch square mesh galvanised welded netting, which is much neater than chicken wire. We bought a 30 metre roll. It is fine wire, almost invisible from a distance, and does not detract much from the view.

A four inch square oak post is set in concrete to make one end of the fence, and this seems to give quite a bit of extra strength and stability to the line of posts.

At the other end of the pond, there’s a short section of the half round 4 inch posts and wire netting plus a heavy gate made of solid one inch plywood, which only an adult can open or close. The gate is crude but effective, pulling in and out of a gap between a tool shed and a wood store and at its other end sliding between 2 stakes. We may replace it with a proper hinged gate, but it seems very hard for a child to open as it is.IMG_4374

The short fence runs up to a small, dense copse, into which we have piled large quantities of impenetrable brushwood.

The other end of the copse is an open gap of 15 feet, then a line of 4 trees, and another gap of 20 feet up to the new permanent fence.

We’ve tackled the two gaps with the old method, using two sections of posts and chicken wire which can be rolled up between visits. One end of each is fixed permanently to trees. IMG_4376When there are no children around, the posts and chicken wire roll into neat bundles which are tied to the trees ready to unroll again. This is far more manageable than the old system, because only a quarter as much netting has to be unrolled each time.

As for the trees, we’ve stapled chicken wire between them and then piled up our stocks of kindling plus some brushwood to hide it, so it makes an impenetrable barrier.

This week we let a three year old loose in the garden, and the fence passed the test, though even so we won’t let children that age out in the garden unsupervised, just in case. Even when they can swim, a pond is not safe without supervision. Nevertheless, the overall result of the work is a secure fence with removable sections which allow us to move freely round the garden when only adults are present.IMG_4383

 

PS on blanket and duckweed as a mulch

Lots of people say blanket and duck weed should be put on the compost heap. Just turned over a year old, well looked after heap, which has been banked up with earth and has plenty of soft material in it, so ideal composting conditions. We discovered none of the pond weeds had rotted. Not such a good idea after all.

However, we’ve increasingly used the pond weeds as mulches to keep the roots of plants damp and to wipe out weeds, and especially the reeds that are trying to conquer the edges of the pond again. So the pond is producing a useful product after all.

Blanket and duck weed again, and other matters

Last year’s big effort to clear blanket weed by physically removing it has paid off, so far. It has been surfacing again in clumps this spring but not nearly as much, so an hour’s work in waders was enough to clear it. Every bit that comes out removes nutrient from the pond, because – looking on the bright side – you could regard blanketweed growth and removal as a way of sucking up excess nitrates and phosphates and putting the pond in better balance.

There is still plenty of it close to the bottom but I suspect that the combined effect of the clouds of daphnaea and the three grass carp – all algae eaters – may be keeping it under control.

Since this is the breeding season for many creatures we pulled the weed out in small clumps and then laid it by the water’s edge so they could escape. We seem to have large numbers of common newts, more than we have seen before, and we made sure they didn’t get trapped. They obviously like it here.

Only very small quantities of duckweed so far. Spoke to a gardener in the neighbouring village of Mellis about his duckweed problem on a pond with perhaps a third more area than ours. He has hauled out tons of it over the years, he says, using similar method to mine, but it covers the surface again within days and even stays there through the winter, so he has given up for the moment and is concentrating on his lovely garden. The whole pond is an unsightly green.

Why is it so intractable? My guess is that it is  partly because the pond has not been cleaned for a long time so it has a couple of feet of mud on the bottom which makes working in it difficult. That also discourages repeat cleanings, which are needed if the exercise is to be effective in any given year. Duckweed survives by sinking to the bottom and lying in a dormant state over winter so old mud may be riddled with the stuff, just waiting to surface if there is any light to prompt it, which would be the case after partial cleaning. Furthermore, the excess nutrients that stimulated the duckweed in the first place stay in the pond and continue to accumulate as the leaves rot, if they are not thoroughly removed. As with blanket weed, disposing of duckweed gets the nitrates and phosphates they have fed on out of the pond.

With a thoroughly contaminated pond perhaps cleaning is the only way to conquer the menace, and of course that’s not something to be undertaken lightly.

Otherwise, our pond revetments have been stable over the winter and no replacement stakes or timbers are needed. Having used softwood instead of oak stakes to hold up the timber boarding for cost reasons, we are expecting to have to replace them every five to seven years but so far there are no signs of deterioration after nearly four years. The softwood boarding, which was double treated under pressure, was claimed by the supplier to be good for 15 years under water.  By then the banks should be well and truly consolidated.

The future

The pond rescue is complete! Two and a half years after we started, we have a stable and attractive pond, which means we’ve come to the end of  the intensive campaign to get it back into health.

Even so, a good pond needs constant, but not intrusive, maintenance. There’ll be the occasional post here about maintenance, but from now on we will report detail of our experience of managing the pond in another more garden-focused blog. Here is a link to  the garden at The Old Brewhouse.

Follow the pond’s progress there.

We’ve printed a limited edition, colourfully illustrated book on the pond reclamation project, which is also available in PDF form for £3 by email from jamesharte36@yahoo.co.uk.

Wildlife, plants, maintenance – 2013

 This post is an update on the recovery of wildlife in and around the pond in 2013, together with an account of the year’s  maintenance issues.

To recap, it was striking how quickly the wildlife in the pond recovered in 2012, the first full year after the mud was removed. The two maintenance issues this year were stopping the blanket weed takeover and stabilising the pond level using the old farm well nearby.

006

A windless morning, late August 2013.

October 2013

Several enormous dragonflies around the pond in the warm spell of the first week of October – same species as the photo below in August. Pond exceptionally clear, with bottom visible even at the deep end. Very few ducks, often not around at all, so there is little to disturb the water. Too much blanket weed across much of the pond, though growth restrained (creatures eating it?) and only breaking surface in one place.

Pump off at the end of September. After a fortnight the water is down 9 cms, to a level about 25 cms below spring maximum.  Weather very warm for time of year.

September 2013

A water vole swimming across the pond. Exciting. After all we’ve heard about their diminishing numbers, we must research the best ways to protect and encourage them. The previous find was of a dead one, which did at least allow time to positively identify it. Doesn’t seem to have been discouraged by Georgia swimming in the pond in the 85 degree Fahrenheit mini-heatwave of early September.

Pond level on 12 September had fallen 16 cms from the spring peak, even with the pump from the well, but in the next three days it rose 5 cms – the weather has cooled dramatically, and it has been raining. I put a notch on a post to measure changes in the water level.

August 2013

Water pumps, water voles and refugee fish

The pond water level is staying constant this month, held there by 2 to 3 cubic metres of water a day pumped in from our garden well from June onwards. The pump is automatic, operated by a float switch, and comes on for short bursts once the well water reaches a certain level.

The pump has a dual function: for much of the year it keeps the water table by the house down, because the well is by the back door and its water reaches near the level of the kitchen floor by mid-winter, which seems a bit of a risk. In June we dropped the automatic pump down a couple more metres than usual which much increases the flow rate. The result is that instead of a pond level fluctuating by a foot or more as evaporation increases in the summer (and willow roots draw more water) we have a near constant depth. Instead of a rapidly changing habitat from deep to shallow as the summer progresses, we have created different permanent habitats round the pond – there are two deep areas, two large shallow areas, and three boggy areas.This makes planting much easier.

Stabilisation of the water level is also much helped by the larger volume since we cleared the mud, which keeps the water cooler, thus reducing evaporation.

Found a dead water vole near the pond. That at least allowed us to identify it carefully from photographs. Great news in one way, in that they are back, but sad in another. Hope it was not the only one. There’s plenty of cover in the reeds now if others are around. Could that rat seen in the spring have been a water vole?

049

A dragonfly that strayed into the house

Lots of dragonflies around the pond this month, not quite so many damselflies. Getting to grips with identifying them now.

Pond has cleared and the blanket weed is mostly confined to a layer on the bottom, looking like underwater grass. Just the occasional cloud of harvest dust descending on the surface, soon to sink. Near the end of the month, some blanket weed breaking surface again in a shallow, warm area. How interventionist should we be? To think about in the next few months. Still thinking about doing an aggressive clean up of the blanket weed in the late autumn.

Ducks are relatively rare this year – only three or four compared with the peak of more than twenty last year. Only two seemed to survive from the brood, whereas last year there were two broods and more survivors. Moorhens are still busy.

Fishy business

Found another three fish escaped from next door, grey and about 15 – 20 cm long. (The smaller arm of the pond goes into next door’s garden through a reed bed). They have been identified as grass carp which, among other food, munch blanket weed. They can grow enormous – pictures on the web of 35 pounders – and eat three times their weight of vegetation daily when mature.

A grass carp

A rather more mature grass carp

This is why they are used for weed control in rivers and lakes in Europe, including the UK, and the US. However, they are classified as invasive in the UK, and controlled. Licences are not needed to keep them as long as the pond is less than 1 acre, not connected to any other watercourse, entirely surrounded by a private garden, and not used for fishing.

It seems they can only breed in running water, but one website specialising in selling them says they can be very determined to find it if the pond has an outlet (which ours does, though only in winter and spring.)  If they are stocked anywhere other than garden ponds, it seems only infertile triploid fish are allowed. Triploids are produced by treating the eggs and then testing the young to ensure the treatment has worked. Amazing what you can find out by typing ‘grass carp’ in a search engine.

I don’t buy the idea that they are good for blanket weed control, because the bulk of the nutrients in the weed will be excreted back into the pond by the fish, raising nutrient levels and encouraging more blanket weed – we’d be farming it. I think mechanical removal of excess blanket weed once a year is better, because the nutrients are taken out of the pond and disposed of away from it.

The neighbours will try to retrieve their fish soon, with our help. If they don’t catch them, and they grow too big, then we may have to start looking up carp recipes!

July 2013

A grass snake swimming in the pond. At least four carp have escaped from the neighbour’s pond across the reed bed that separates the two. He has put out a fish trap to get them back! The neighbour did put up a small mesh wire net across the reed bed, but it seems it was after the fish had bolted.

Also found a couple of leeches in the blanket weed when that was being removed. No sign of the weed regrowing, but there is now some duckweed. Lots of bright blue damselflies and some brown dragonflies.

June 2013

The blanket weed still spreading early June, and blocking light and clogging the pond. Decided on more vigorous action: have been clearing the pond about 30 or 40 sq metres at a time with a grass rake, partly from the edge and partly using waders. Six wheelbarrows heavily loaded after clearing about half of it. Even though this is a very active time of year for pond life, the thought is that each section will have time to recover and animals can also migrate from the disturbed area, when work is being done, into cleared areas.

Checked after clearing the first couple of areas and teeming again with underwater creatures. Have actually been raking the bottom to get up as much as possible, including last year’s dead leaves. It is clear that a large part of the rotting debris on the bottom is last year’s blanket weed.

In the autumn, I plan to rake out all the debris after leaf fall in the hope of reducing next year’s nutrient content, because it is high nutrients that encourage blanket weed. Not too worried about damaging wildlife given that the pond was full of it within months of digging it out and refilling in 2012. But best done thoroughly in the late autumn.

Where are the nutrients coming from? The likeliest source is the cleared pond mud. The banks are of pond mud held back by planks, so nutrients in the mud are likely to be leached into the pond through the gaps in the timbers, especially after the heavy rain of the autumn and winter. The more we can grow on the banks the better because plants will use up the nutrients.

Other possible sources are next door’s chicken run, from which runoff may reach the pond in heavy rain, and the well water which we are pumping in to the pond to maintain the level in dry periods. The well is shallow, only 20 feet deep, so it is possible it may be contaminated by fertiliser. We will buy a testing kit and see. But the volume is only a small proportion of what is in the pond so it does not seem the likeliest suspect.

There are also rotting leaves on the bottom but since there has only been one season since the pond was cleared this seems unlikely to be the cause of a large excess of nutrients.

Plants round the pond thriving.

April and May 2013

No shortage of frogspawn and tadpoles.

Newts not yet seen. Vast clouds of daphnaea on a sunny day.

Blanket weed is a much bigger problem than last year, in some areas blocking the sunlight very thoroughly, so we are gradually clearing it, a patch at a time. This risks some damage to pond life, because of the time of year, but on balance the blocking of sunlight and the effect of the dense mass of underwater vegetation could be more damaging if there is no control – that’s our theory, anyway.

Some sources say clearing releases spores and makes blanket weed grow faster, but it is hard to imagine it growing faster than it does already. The Royal Horticultural Society website does not in fact mention the release of spores as a threat and its first suggestion (in a long list which we may have to work through) is to twirl the weed filaments on a stick and pull out. A grass rake proved to be much more effective.

In late May, we saw a large brown rat : disappointing, because we were hoping for the return of the water vole. The rat jumped out of the pond at lightning speed when ducks landed nearby and ran straight across Peter’s foot in a panic. Later it was seen slinking into next door’s chicken run. The rat could explain the number of freshly eaten duck eggs in the grass.

First swim – 2012

The pond depth was swimmable from April onwards, but the incentive to take a dip lessened as the cold, wet summer dragged on.  At least the rain kept the pond full and the water mostly clear, though for a few hours each day it was crowded with ducks – we counted 19 one day – that seemed to prefer us to the other nearby ponds.

Peter swimming the first length, after first tending the water lilies.

Finally, Peter, Cai and Georgia went swimming in August 2012 . The first time, the water was surprisingly cool, especially at the deep end, but no worse than any unheated swimming pool . The chill disappeared completely by the end of  August.

Cai Pritchard gets ready for some wild swimming….

Swimming was a good opportunity to move some of the water lilies which had been planted in tubs on the bottom, three of which seemed not to like the deepest water.

The first swim was just in time, because a few days later a sudden bloom of green algae, probably encouraged by the hot weather, made the pond uninviting for the week that it lasted.

… and takes the plunge into the cool water.

The bloom then disappeared almost overnight, and the water was inviting again.

Georgia in the pond

And here’s Georgia, who swims regularly in the open air in Highgate Ponds, doing some Suffolk wild swimming, after diving in at the deep end and scaring away all 19 ducks, not to mention the 6 moorhens, who scuttled off in all directions. We’ve been wondering how to limit the bird population, so maybe this is the way to encourage them to spend more time in the neighbours’ ponds.

Georgia dives in (the camera wasn’t fast enough!)…

…and does a few lengths.

By late August, the  pond was nearly a foot lower than its mid-summer height, but it was still possible to swim almost the full  length.

Filling – 2012

Early February

Frozen in early February

A skating rink – if we dared. Most of the bottom covered, but still about 60cm lower than previous winter level, mainly because the water has first had to fill the volume left by removing the mud. Frozen and smooth, and can just about walk on it.

Equinox 

The water is now exactly back to the level of the mud before it was removed, so there’s still quite a way to go – but it has been a very dry winter.

6 weeks later – more water

At least 30cm more water needed to reach the top of the revetement.

Mid April

The rains begin, making up for the drought.

April 2012, nearly full and most of the posts cut back

Still filling – 12 cm in 3 weeks. About 30 cm below old springtime level.

Mid-May

A very wet spring, though still officially a drought.  The pond is back within a few centimetres of  its old spring level, before the mud was cleared, and almost all the timber revetements are under water.

Early June

The last of the meadow mud pile is cleared by barrow, and used to landscape the far end of the pond with a gentle new slope up to the hedge.

In late May the pond water level dropped 6 or 7 cm from the peak, but it has started to rain again this month and the level is stabilising.

Question – at what level will the pond water stabilise in the summer and autumn?

We’ve been measuring the ground water level as indicated by the 5 metre deep well nearby, and the indications are very positive for the health of the pond. As the well water rises to its normal spring level of about a metre below ground, the pond seems to be taking in groundwater from the bank near the well, together with rainwater. We think the groundwater is seeping through a layer of sand near the bottom on  the north side, which is about 25 feet from the well. When building the revetement on that side, we protected the sand layer – and any possible water flow through it – by putting gravel and geotextile behind the timbers.

The pond level certainly seemed to track the filling of the well after the drought ended. So the pond seems to be receiving direct rainwater, rainwater from the gutters via the drains, and ground water as soon as the water table rises.

But during the drought the water in the well – and so probably the water table – fell to about the level of the bottom of the pond, so groundwater seepage would not be much help in times of shortage.

There are several positives:

We hope that now the pond is so much deeper it will stay cooler and evaporate more slowly than in the past,  so there will be enough cool water to act as a reservoir during dry periods.

We’ve also removed some of the trees round the pond, so the take up from roots should be less.

Finally, the well and its pump can be used if the pond does fall too far.  The well did not run dry even in the worst of the local drought. There was never less than 2.4 metres of water, and the pump – even after several almost rainless months – managed to produce two or more cubic metres of water a day in a test run, without the output slowing. We have been told that the farmer who used to own the property maintained that if he filled his irrigation tanker with water, the level in  the well would recover by the time he got back from the field to fill the tanker again.

We will monitor the pond level all summer.

July

No need, after all, to worry about the pond level this year –  rain, rain and rain again through July, and the pond has stayed at its spring peak. We were away for several weeks and came back to find the garden growing like a rainforest.
August

The weather looked up and we had our first swim – see separate post. The pond remains full, but has retreated about 10 cm from its spring level, measured against a notch cut into a post, which is still a good summer level.

Pond full and clear

We  also did some tests on the nearby well to see how much it could supply in these conditions. At a rough estimate, it seems to be able to produce 4- 5 cubic  metres of water a day, compared with about 2 cu metres at the height of the recent drought, when the well level was about 2 metres lower. Our pond is about 250 sq metres, and next door’s, to which it is connected through a reed bed, is around 100 sq metres, so on that basis the well could increase the pond level about 1cm a day, excluding evaporation and extraction of water by roots. A separate very rough test (over too short a period to be definitive) suggested that on a hot day the pond level might be falling about half a centimetre, so the well seems capable not only of offsetting a fall of that size but raising the level in summer. But, tests aside, it is probably best to let the pond level drop naturally in the summer, so that it will have more capacity to absorb winter rains.

September

Measured water level, which by 7 September was 21 cms below its late spring maximum, though there was still a reasonable depth of water throughout the area of the pond.

September, when the level was at its lowest

When the pond was full of silt it warmed up to almost  bath temperature on a hot summer day, but with a much larger volume of water the temperature has stayed down and the evaporation rate must surely be lower. Even on the warmest days, it was rather chilly to swim in.

October

Heavy rain, so pond level starts rising again mid month, helped by lower temperatures and probably less extraction of water by tree roots as the leaves begin to die and fall. (The low was in mid-September, 25 cm down from the spring level). This is excellent news, because we can now be pretty confident that cleaning the pond has not only ended the cycle of summer and autumn drying and spring flood, but has kept the level much more stable than in the past, confirming that it does not leak. The water has also been pretty clear and quite sweet smelling, without that unpleasant stagnant stink that it produced in the summers when it was full of mud.  It is of course an odd year, with record rainfall, so it may perform differently next year, but it now seems very unlikely to dry out again.

We have a secret weapon if the level does fall uncomfortably low in some future drought: we tested the well, which is 25 feet from the pond, and it produced more than 2 cubic metres a day at the worst point of the drought last year when the water table had gone very deep, and far more, of course, in this year’s rain. So an electric pump has been rigged with a conduit into the pond. We will not try to keep the pond at a constant level, and will let it fluctuate naturally, but within boundaries.

In October it was filling again

If we have another drought and the pond level falls more than 25 or 30 centimetres from the spring height, then we will use the pump to stop the water falling further. Water extraction licences are only needed for farm wells producing more than 20 cubic metres a day, and hosepipe bans don’t affect private wells. We can also divert the water to the garden in a drought.

November

018

A calm day in late November

Rain and more rain. The pond was back to its maximum spring level by the end of the month. It looks as if it will reach the overflow shortly, which in the past hasn’t usually happened until the spring. The overflow leads to a depression in a neighbour’s garden  which we think may have been a part of the pond. In very heavy flooding it should flow through from the depression into a ditch which passes through a pipe under the road into a pond in another neighbour’s garden. That pond in turn has an overflow into a stream which flows into the River Dove and then the Waveney, ten miles away. That is the plan – hope it works, or the road will be flooded.

Autumn reeds

Autumn reeds

Because we removed two large ash trees which were leaning over the pond, and threatening to topple into it, there has been much less leaf fall this autumn than in previous years.

The owl failed to deter ducks from eating new leaves on the water lilies

The owl – a failed duck deterrent

We are debating whether to disturb the pond by raking out some of the leaves that have fallen in and sunk. Is it best left undisturbed or should we try to reduce the amount of organic matter? What would be the effect on wildlife? Would it release algae spores and encourage them next year?

There is also a duck problem: half a dozen on the pond are lovely, but the two dozen we regularly have are messy, trample new plantings by the edge and eat the buds and young leaves of water lilies and bog bean. Nobody has the grit to kill and pluck them for freezer, and it is hard to think of a compromise way of deterring some but not all of them. We’ve made the pond too attractive!

December

011

Ice and frost

017

…and sun

Started dryer, brighter and colder, but the grass was still growing, just. Then a heavy frost and the pond froze, another thaw, and day after day of heavy rain, so that for the first time we had a stream flowing out of the pond, through a pipe under the road and into the next pond, which in turn overflows into a bigger stream. With the overflow working, the pond has now reached its highest possible level, a year after it started filling. On a rough estimate, the flow is enough to change the water in the pond every 10 days or so, which will help keep it clean and fresh.

A stream flows out of the pond

A tiny stream flows out of the pond

The ponds are connected, which helps explain why some of the wildlife came back so quickly.

January 2013

A quiet and very wet month.

February 2013

A brief spell of snow

A brief spell of snow

The pond froze, but not for long. Getting the overflow through to the next pond down the slope (across the road) has prevented floods, so the maximum height of water is now set. This completes four seasons since the pond was cleaned at the end of 2011.

How we did it in detail

We had five summers in our house before we tackled the pond properly, including a trial dig in the third summer and autumn when we desilted a section of it. There was time for serious trialling and surveying, which are described in a separate post. It was important to estimate the amount of mud, so we could decide where it could be dumped.

April before the big dig – looks OK, but only a foot of water

We worked out that we could just about dispose of all the silt in the garden, most of it by shrinking the pond and using the silt to build out the banks, reducing the pond area of about 350 square metres by perhaps 100 square metres. The rest could be piled up to rot for a year and then spread over flower beds, the vegetable patch and parts of the garden. In shrinking the pond we decided that the new edge would go along a contour where the mud was about one spade, or 25 cm, deep. This line was marked out with sticks. The result of doing this was to narrow the pond in a way that made it look more like a moat.

Having estimated the scale of the job, we decided to do as much as possible of the work by hand, for several reasons: we wanted the exercise (seriously); the slow pace would make it much easier to determine the new outline of the pond and build up a wall to contain the mud as we went along, rather than have the silt dumped by an excavator in great slippery piles over a couple of days; we were concerned that the clay bottom might be fragile under the weight of a big machine, and that it would be difficult to repair; we wanted to examine the silt and the clay bottom as we went along, to check for interesting artefacts (sadly, there were hardly any); and if there was any other evidence of the pond’s history, we wanted to preserve it.

Our resolve was shaken when one of the contractors told us that to clear the pond with shovels and barrows would take 10 men 2 weeks, or 100 man days. This proved to be an exaggeration. When we got down to it, about two thirds of the mud volume and three quarters of the area was cleared by one person in about 80 hours of actual shovelling time. Pro rata, hand digging proved to be far faster than had been claimed. Our job was speeded up by the decision to dump most of the waste around the edge of the pond. Well over half could be thrown or walked a short distance and dumped, rather than loaded into wheelbarrows, which slows progress considerably.

Timber in place, waiting for machine – hand digging nearly finished

We did eventually hire some mechanical help. This was after we had decided to drop an earlier plan to spread the digging over two years, which would have involved building a temporary sandbag barrier at the point where the first season’s dig ended, to prevent the remaining mud slipping back into the excavated areas (see planning, trialling and surveying). But by mid-October it appeared that hand digging the whole of the rest of the pond would not be finished until end November at the earliest, and winter rains were approaching – or so we thought at the time, though it turned out to be the dryest autumn anyone locally could remember.

We had bought a submersible electric pump with a long lead and hose from Screwfix to clear the water that accumulated where we had dug. (We emptied it onto a grassy area, which was by then so dry that it could absorb hundreds of gallons an hour without forming a pool). Our trial dig two years earlier had shown that once the rain started the mud quickly softened again and became difficult to handle, and especially hard to control when it was piled up, so a pump probably would not be enough to keep the mud firm enough to handle easily. There was also a lot of finishing work to do after the basic digging, and it seemed important to have the pond ready to fill again rather sooner than Christmas. We were also concerned at the effect of deep-freeze weather, like December 2010, because solidly frozen clay seems to become friable when it thaws, which might damage the water retaining properties.

So we called in a mechanical digger and expert driver from a neighbouring village for half a day.

Tackling the last few tons of mud – grey bottom clay visible.

The pond has good access, a feature of its central role in the farm. The contractor suggested he bring his biggest machine, a 13 ton monster, which has an arm long enough to dump silt in precise positions over a wide area without moving its tracks much. We asked that the digger’s tracks should stay on the hard area of the bottom that had been used by farm carts.

The result: the rest of the mud was shifted by an expert operator in 3 straight hours, with the rest of the hire time spent getting the digger in and out of the pond and cleaning it.

A lot of the mechanically-dug silt was put around the edge, but we did not wish to shrink the pond further. So we also accumulated a pile of silt about a metre deep in an area about 8 metres by 8 metres on a patch of rough grass in the garden. This is being left to rot down over the winter and it will then be shifted round the garden and distributed in thin layers. There will probably be a couple of hundred wheelbarrow loads to move.

Left-over mud, piled in the garden

The number of man hours we worked to finish the project totalled 165, which is 28 man days if you assume 6 hours hard graft during an 8 hour day (and the other two hours for meals, tea breaks and leaning on the shovel to contemplate the excavations or the moorhens, or to talk to the neighbours).

The overall cost of DIY in labour and materials, spread over three months, was £1,967. All but £400, for hire of the digger and driver, was for materials: timber, cement, gravel, hessian sandbags, geotextiles and tools (see the post on materials and costs). The finishing work, including the construction of containments to stop the mud slipping back into the pond, took about as long as the hand digging.

If we had a garden big enough to dump the silt out away from the pond instead of putting most of it along the perimeter, we could have relied on the existing banks and avoided purchasing timber, sand, cement and hessian bags. The total cost would then have been less than £800. Digging would have taken longer, because there would have been further to move the material.

Some might say we were mad to dig so much of it by hand (though there were good reasons for doing it, explained above.) It seems likely that the whole pond could have been cleared by the digger in 2 or 3 working days at £500 a day. This was a very large excavator, and with more restricted access a smaller machine would be needed, which would take longer. We estimate that if the whole pond had been dug mechanically with the big machine it would have taken the cost to £2,600 – £3,000. Again, if we had somewhere to put the silt in the garden away from the pond, we could have saved £1,200 on materials.

If you want to do it all mechanically, don’t go to an expensive specialist pond contractor but find a skilled local builder who can excavate under your supervision at a fraction of the cost. One caveat is that it may not be the right solution if your silt is very liquid or if you can’t fully pump out the pond.

There are a number of differentways to contain silt once it has been dug out, explained in the planning, trialling and surveying post. When under the water in the spring, our pond mud was almost liquid, so a bamboo pole dropped vertically (as an experiment) went well over a metre down at the deep end under its own weight alone, which was why we were so scared of falling in there. Once dug out, mud of this consistency needs to be contained in extensive ditches or held back by geotextile barriers to drain. This is time consuming and potentially expensive.

But the key to our job was that in 2011 the pond dried early, helped by some pumping in the early stages. From August, the ooze consolidated rapidly, and within two or three weeks much of it began to behave like damp garden soil, and could be stacked more than a metre deep without running quickly away.

Sketch diagram of the pond before and after

The stacked mud still needed a timber containment to stop it creeping along slowly over the days. First, we used scrap timber we had saved from building work on the house to build a rough and ready revetement, or timber retaining wall, pinned back by softwood stakes driven into the bottom, to hold each section as the mud was put behind it while the dig progressed. The fresh mud, while moving slowly, exerted tremendous force. This first defence collapsed in one 5 metre long section of the 80 metre perimeter, and had to be remade, and the mud shovelled back again. But a month later that mud pile had dried to the point where it was stiff enough to walk on.

The biggest materials cost was new treated timber to build the main revetement in front of the scrap timber barrier, using treated softwood planks laid three, four and five high on top of each other (depending how deep the pond was at each point). This was the timber which would be visible around the edge when the pond was finished. The timbers were to be supported by round softwood posts driven into the pond bottom.

We knew the maximum depth of the water above the mud (assumed to be flat) in the spring, which was about 40 cm. So the timber needed to be 40+25 cm high, ie 65 cm. We settled for 60cm of timber, which is four 15 cm wide planks on edge. The shape of the pond meant that in one short stretch five planks were needed, and in several other short stretches only three were needed. We could then estimate the length of planking to order from the length of the sides of the pond.

Timber to reinforce the bank

We included two concrete sections, one 4.5 metres long and the other 6 metres. They were built from hessian sandbags filled with a dry mix of 5 sand, 1 gravel, 1 cement. The bags will biodegrade, and waterside plants will be used to camouflage the concrete. The walls were in two places where the bottom went down sharply. This structure followed the contour better. We placed the bags in position as soon as they had been filled, because they hardened overnight. We did not bother with foundations, but did level the hard clay bottom before placing the bags. We used a single line of sandbags laid lengthwise.

Sandbags filled with concrete

One of the concrete sandbag walls was built to hold back the mud and roots of a reed bed which we wanted to preserve at one end of the pond. We also used gravel and permeable geotextiles behind the timbers along the short section of the edge where groundwater enters the pond, to help that flow.

In the shallowest part of the pond where the new work would be most visible, we used felled timber and rough sawn pine sleepers as edging. The felled timber we had available was willow, which is far from ideal, and tends to sprout, but it was that or ash, which was more useful as firewood.

Work at the shallow end

More concrete in sandbags and a short timber revetement. The smallest of the old clay diggings is visible.

Finally, we used 3 tons of gravel to firm up the bottom of the pond by making paths, which will be used for maintenance, wearing waders of course. This was essentially what the farmers had done, by dumping tons of gravel and stone in the middle to prevent their water carts sinking into the bottom clay.

The pond from the south end showing the concrete-filled sandbags

The pond from the south end showing one of the two sections of concrete-filled sandbags, positioned where there seemed to be a risk of slippage of the piled up mud.

In mid-November, three months after we started, the pond had been completely cleared and the timber and sandbag work finished, together with a gravel path all the way round the edge and across the middle. The path is to be underwater when the pond fills, to make maintenance easier.

Finishing work

There was much finishing work to do.

In March, the posts were tapped with a sledgehammer to check that ice, rising water and a softening bottom had not loosened them. The tops were trimmed off at the same time.

Some of the top planks loosened as the water rose, and two or three floated loose. They were put back and nailed. But nails proved unnecessary, because it was easier to secure loose planks simply by ramming down the mud immediately behind them and raking mud from higher up into any voids. The friction of the rammed mud was enough to keep the planks down. To be sure, we rammed the mud down behind all the planks, not just the loose ones.

We also moved many hundreds of barrow loads of mud from the large pile of left-over spoil which had had to be stacked in the garden (see picture above). This pile proved very useful for adjusting the profile of the pond banks, because in some places the new mud settled further than in others, mainly – we think – because of varying amounts of clay in the mud itself. Mud into which a lot of clay had fallen from the pond sides consolidated very quickly, while soft mud from the deep water continued to shrink for longer, a process that is likely to go on for several years, judging by the results of the 2009 trial.

Even after this fine tuning there were still tens of tons of spoil left. This was taken to the far end of the garden and deposited to form a low terrace, which will be ready for planting next year.

These landscaping jobs were spread out over six months, so we could judge how the spoil was settling. So the final barrowload of pond mud was not shifted from the pile until early June 2012.

Wildlife and plants – before and after

This post starts by describing the wildlife and plants we found before the pond was cleaned, and then goes on to a monthly diary for 2012, setting out how the pond and its surroundings are evolving in their new form, including our new plantings.

What we found

All the printed and web authorities on the subject say that before restoring a pond it is important to know what plant and animal life is being disturbed and to plan strategies to minimise the damage, if possible phasing the work over more than one season. Some also suggested we should commission a proper study by a professional ecologist. But we already knew something about the costs of doing that: we spent £400 on a survey of the orchids in the garden, which proved to harbour species together with a rare viper’s tongue fern. The orchid survey was a condition of our planning and listed building permissions for repairs to the house.

Instead of hiring the ecologist again, we kept our eyes open and also consulted the previous owners on what they had found over the years. We quickly came to the view that the wildlife in the pond was in decline and that as the silt deepened it was somehow throttling plant life and discouraging insects.

Ducks in early summer – contributors to the deterioration of the pond

The previous owners reported that the pond had once contained crayfish and that a water vole had lived in the bank. We saw no evidence of crayfish. The only animal swimming looked like a rat from a distance, but on reflection may well have been a water vole. There was no sign of Great Crested Newts, but each spring there was a large quantity of frog spawn. The eggs hatched well before the pond dried. Almost every day in the summer we came across frogs, small and large, that had fled the pond and were living throughout the garden in every patch of long grass or pile of twigs. We very much hope that when the pond settles down again it will attract back all these creatures apart, perhaps, from the rat.

In the first couple of summers, there was also much insect activity on the surface of the pond, with water boatmen and other surface skimming creatures, and crowds of midges later in the season. But within a couple of years only the dragon flies and the midges persisted. We now suspect that the diminishing of insect life after the third year may have been caused by our first trial attempt at clearing part of the pond, when we removed mud at one end. Disturbance of the silt released bubbles of foul smelling gas. Who knows what noxious substances our spadework stirred up from 80 years of deposits in a farm pond. Repeated examination of the black silt showed no evidence of any creatures visible to the naked eye. It seemed to be inert.

There was a pair of moorhens, which nested in an ivy covered tree stump next to the pond and stayed with us each summer until the last drop of water had gone, as did the two or three pairs of ducks which were regular visitors. They hatched and trained broods of up to a dozen ducklings before the water disappeared in August, scouring the mud for food until the surface began to dry hard. Since we could find no evidence of animal life in the mud, we wondered what the ducks were eating. Perhaps fallen seeds? While the pond was being desilted, the ducks deserted us, but the moorhens and their half grown chicks returned to their home each evening, and bathed in the puddles that were left.

Ducks are a problem, but also a delight. The Suffolk Wildlife Trust and a charity called Pond Conservation both advise against encouraging them. They stir the water into a muddy soup, enrich it too much with their waste and are ravenous feeders, so that ponds with large duck populations tend to be bleak and muddy and afflicted by algae, which blocks light and slows other plant life. The wildlife trust advises against feeding ducks, which encourages more to come.

We made a duck island – but it attracted too many ducks. It has been taken away.

Our pond was certainly popular with them in the spring. One day we counted 20, including 7 chicks. They were an endless amusement, fighting, feeding, taking off and landing; but the water was so shallow that it looked like suspended mud when they fed, which was by shoving their bills through it. Stirring of the sediment may have been one of the main reasons for the lifelessness of the pond. When the pond is desilted the water will be much deeper and there will be large areas where the ducks will not be able to bottom feed. We hope this will deter them. A couple would be perfect, but 20 are a real nuisance. The drawback of a deeper pond, according to the Wildlife Trust, is that it encourages fewer species of plants and animals. But our view is that the advantages of a cleaner pond make it much the best option.

The plant life in the margins of the pond was dominated by Reed Mace, yellow Flag Iris and some unidentified smaller reeds, all of which are useful for water purification, water mint and clumps of Kingcups (Marsh Marigolds).

Iris thrived

Wild roses and brambles tumbled over the edges.The only plant life actually in the water was blanket weed choking the bottom and floating to the surface in the late spring and a bloom of duckweed that smothered everything in the summer. The duck weed has disappeared since the first dig into the silt.

Duckweed taking over in early summer, reeds encroaching

There was a riot of pussy willows at one end, and a line of enormous ash trees down one bank, two of which were leaning over the pond and on the point of collapse , so were removed. Hazels, hawthorn, blackthorn and field maples also shaded the pond.

We cut back most of the small willows, and trimmed a giant willow, which was leaning and at risk of collapse under its own weight. One reason for pruning and removing trees (mostly done by a professional tree surgeon) was to increase the amount of light and reduce the leaf fall, both of which will help keep the water healthier.

Pruning the ash trees by the pond

We will update later on how quickly the animal and plant life returns. To speed the process, we intend to plant soon Glyceria Fluitans (Floating Sweet-grass), which we have seen described as a water vole”s favourite food. We are also thinking of planting – in addition to the existing yellow Iris, reed mace – bogbean, water mint, flowering rush, water forget-me-not (in the shallows), and one or two water lilies. We have yet to decide on the oxygenators, such as rigid hornwort.

Month by month

February 2012

The ducks have returned, sometimes six or seven, but the water is already too deep for them to feed in the middle. Even so, whenever they feed round the edges the whole body of water goes muddy. Moorhens back.

What looks like blanket weed is visible, growing close to the bottom at this stage.

Some watercress-like plants, yet to be firmly identified after consulting several reference books and the web, are thriving round the edge on the new banks, and some seem to have found their way into the water and are growing on the bottom. This is a plant that spread rapidly on top of the mud each year as soon as the pond had dried. We must find out what it is and whether it is invasive. It is also growing in the roadside ditches nearby.

March 2012

Pond filling, though still about 30-40 centimetres lower than its normal spring level. (Headlines in the papers about the worst drought in East Anglia for a hundred years.) A start made on planting: three buckets with water lilies – planted in loamy soil with gravel over – placed on the bottom in 60-90 cm of water.

Just planted a water lily – slippery bottom, so carrying a stick for balance.

The first bog garden has been created at one end of the pond, behind a 15 cm high brick and stone barrier, which will eventually be under water. The barrier is to stop the mud and compost mixture in the bog garden sliding back into the pond. Planted bog bean, yellow Iris and Primula Florindae.

Floated three pieces of Water Soldier in the pond, having checked that it is easy to control.

Frogs mating in the overflow pipe. Not much doubt that amphibians will like the pond. They are so hardy. This month we discovered a large toad living at the bottom of our well, nearly 5 metres down. At first we thought it must have just fallen down through a crack in the cover. But then a day later we spotted a small, young companion. Is there a complete ecosystem (of food and mating toads) down there? To investigate further. The big one looked fat and healthy from a distance. Could this be the first line of a new Grimm tale: once upon a time, a toad lived at the bottom of a deep, deep well…..?

Kingcups reappearing at the pond edge. And then the frogs came back….

Frogspawn appears

April

Tadpoles hatched. Thousands of tiny black insects, too small to tell whether beetles or flies, are jumping about above the surface of the water – like fleas? What looks like a mosquito larva floating just under the surface. Two broken duck eggs on the grass, away from the pond.

Very large amount of floating blanket weed appearing on the surface, removed with a grass rake and left on bank edge for trapped creatures to get back to the water.

Burrows that may be water voles have appeared near water level. Water boatman. Daphnaea in large numbers, a freshwater shrimp.

Kingcups in flower and flourishing again. Water lilies showing stems and leaves but haven’t broken surface.

Barn owl a regular – swoops around the little field across from the end of the garden.

Planted reeds (growing in pile of pond mud) around edge in some places to speed consolidation of mud, in the hope that they won’t spread into the pond now the water is so deep. If they do, the new clean bottom will allow us to get at them and cut them back. Also planted watercress-like plant around the edges (still not identified) because it spreads rapidly but is easy to pull out if it becomes invasive.

Gunnera Manicata seem to have been a victim of the winter, or maybe the earlier drought.

May

No sign of the blanket weed reappearing. Book says daphnaea are voracious eaters of algae, so maybe they are helping.

Kingcups still flowering. Astilbe growing in pots by the pond while we think of where to put them. Rheum Palmatum ditto.

Kingcups

One of the Gunnera showing signs of reviving. Planted several more.

A birch sapling planted a couple of metres back from the pond. Also planted water mint.

Water lilies seem to be fighting a losing battle against the ducks, which seem to break the leaves as soon as they reach the surface (or is the moorhen the guilty one?) Only the water lily in shallow water is thriving. The others send up shoots regularly, but then the leaves are attacked.

June

Gunnera now starting to establish itself, and this year’s planting doing better than last year’s. Moved Primula Florindae from a boggy area to a slope just above the pond.

Gunnera manicata


Pond warming up.

Watercress-like planted identified as Water Forget-me-not, which is spreading, and beginning to form rafts stretching out from the pond side. Rushes and reeds growing vigorously.

July

Very wet month. Large numbers of frogs in the garden. Irises flowered.

Planted water mint close to but not in the water. Bog bean beginning to grow after nearly disappearing. One of the water soldier plants is now enormous, having reproduced the original spray of leaves many times. A second one is much smaller. Can’t see the third at the moment. They were not planted but just put into the water. Put Carex Riparia, a grass-like plant, next to the water. (Can also be planted in the water.) Only the water lily in shallow water (about 50 cm) is thriving. The three in deeper water are struggling and one is not visible.

Two families of ducks have appeared, one with eight large ducklings and one with two small ones. The large ones must have hatched elsewhere. They have been diving deep and coming up with beaks full of what appears to be blanket weed. From time to time they disappear, to one of the three ponds within a couple of hundred yards. There are also two moorhen families, each with two chicks.

August

Warm weather, and a bloom appears on the surface. Concerned that it might be blue-green algae brought in by the ducks, but couldn’t positively identify it from web pictures and descriptions. Greeny brown rather than blue green. No structure visible to the naked eye – more like dust, but thickens up rapidly. However, after a week, it disappeared – in two days – leaving the water clear. Started pumping in much colder well water when the algae appeared, to see if lowering the temperature of the pond would make any difference. But no way of knowing whether this had any effect, because the bloom might have vanished anyway.

Dug over and cleaned up the large area covered by the mud pile in the winter, which was already being conquered by aggressive plants such as hogweed. Also cleared the ground right down to the pond on that side, and sowed the lot with grass seed, including some mixed wild grasses bought from theseedstore.co.uk. The plan is to keep it as rough grass rather than make a lawn. It will complement the even rougher grass in the meadow area which it adjoins, where we have orchids and fritillaries.

Planted the chocolate smelling Cosmos Dentata on a bank above the pond and Ligularia, with large burgundy leaves, right by the water, though not in it.

Cosmos dentata (chocolate)

Ligularia Britt Marie Crawford

Primula Florindae doing very well in its new position, a foot above the water rather than with its feet wet.

Prepared another small boggy are for future planting.

Far larger number of frogs around in the grass than in previous summers, presumably due to the wet weather.

Cleaned up the massive new growth of weeds and brambles on the west side side of the pond to expose the Rodgersia and Acanthus planted last year, which have survived the encroachment.

The coppiced hazel is growing back strongly right by the pond, and a sapling nearby seems to be trying to catch it up. We will keep both. There is also a field maple sapling by the pond which we will try to grow into a bush (because as a tree it would add too much shadow to the pond).

Water lilies, not yet flowering

Moved the three water lily tubs in deep water close to the one successful plant in shallow water. Needed a swimming costume to do it, because the water is far too deep for waders. The tubs have handles on them which makes it much easier to lift them. Two plants had some shoots and leaves but the third showed no evidence of either. All three were repositioned close together. If depth was the problem, then four feet of water is too much for this variety. Another explanation is that because they were placed deep, and sent up very long thin shoots to the surface, they were more vulnerable to accidental or deliberate damage by the large number of ducks on the pond.

September

Most of the new grass by the pond growing fast. It was given cut in the first week of the month, helped by the ducks and moorhens, which are grazing it (too energetically, in some places.) Planted two Eupatorium purpurea from Beth Chatto, where we saw it 2 metres high, near a pond. Water soldier seems to have broken up and sunk, after some of the 19 ducks were seen diving energetically around it, feeding on something close by or on it.

A moorhen struggled back into the pond with a broken leg, and hid in the reeds and hid in the reeds, calling in distress. Curiously, we saw none of the 6 moorhens on the pond the next day, and wondered whether the by now fully grown ducks had turned on them, breaking the poor bird’s legs. It has been war between ducks and moorhens all summer; the latter have a reputation for killing ducklings by grabbing them by the feet and dragging them under water, and they regularly chased away the ducklings when they got too near the reeds, so this could be the ducks fighting back. Later, we saw one of the ducks eat a quite large frog that had got too near, so their beaks seem powerful enough to break a moorhen’s legs.

October

Plenty of planting to do, after a visit to Crown Nursery at Ufford. Five Cornus sibrica alba were planted close to the edge of the pond, after clearing a patch of reeds to make way for them; we dug down about a foot to get out the vigorous roots, and refilled with clean garden soil. The Cornus have been planted for their red stems. We also planted two red-stemmed willows, a gift from a neighbour who found that they had seeded themselves in his path.

The new grass has thickened well and the bare patches have filled in.

November

Another visit to Crown nursery at the beginning of the month to buy Taxodium distichum, a swamp cypress which, as its name suggests, is perfect for the edge of a pond, and has a beautiful brick red autumn colour that can compete with any maple. The new tree is 6 foot tall.

The reeds are dying back, after growing vigorously well into the autumn. There will have to be a campaign to hold them back next year. They are very attractive, and good at consolidating the soft banks, but they are extremely invasive, wherever there is damp ground. The plan is to build the reed equivalent of rabbit fence. Rabbits of course need a fence that goes below ground as well as above. For the reeds, geotextile will be inserted along a trench about a foot deep that will then be filled in. This underground barrier should corral the reeds where we want them.

The ash disease is big news, especially in Suffolk and Norfolk. Diseased trees have been identified only a few miles away. and we have been looking out for signs of it in the garden. We have been helped by Ashtag, a new iPhone app designed for reporting diseased trees. It has an identification guide on it.

Two neighbouring gardens as well as ours are dominated by individual large specimens, and it is hard to imagine what the hamlet would look like if they had to be felled. So far there has been no obvious sign of the disease. But we have decided to plant potential replacements preemptively in case the disease does reach us, so that whatever we put in has a head start of a few years.

006

Corkscrew willow

T

Ash trees after pruning

The big question is what to plant. Disease resistant ash? But reports suggest it could take some time to identify and propagate them. Black Poplar, perhaps, because it grows fast and has an attractive shape? Weeping willow? Another corkscrew willow, like the one we have already planted? Or we could go for slower growing trees. We have already planted a Holm Oak not too far from the ash, and two English oak have seeded themselves nearby and are now the right size to be moved. But we can’t wait for an oak to grow…

We are working on ash at the moment for a different reason. The trees we felled a year ago are a superb source of firewood that will last several years. Even very large sections of the main trunk split easily into logs that burn clean and hot. We have five or 10 tons of it to use up over the next couple of winters.

Ash logs waiting to be split

Ash logs waiting to be split

We also thinned our big specimen tree on the advice of a specialist. It only has a root system on one side because it is on the edge of the pond; he thought that, because of this asymmetry, its weight distribution high up could have dragged it over in a gale. As well as this pruning, we removed two medium ash trees that were leaning out over the pond at a crazy angle and looked about to topple into it and four smaller ones growing in the hedge.

December

001

Rescuing old vines from Ickworth

013

Frost on the reeds

Frozen ground round the pond, which had risen almost to the newly planted Cornus as the wet weather continued. No more pond-side plantings, but we did buy two 16-year-old vines from the walled garden vineyard at Ickworth, which is being dug up on the orders of the National Trust, which for reasons that nobody understands wants to turn it back into a pastiche of an Edwardian kitchen garden. (Shame – even the red wine is good.) The vines have been replanted 50 feet back from the pond. Fingers crossed that they thrive as well as they did at Ickworth. Meanwhile, the frost is decorating the dead brown autumn foliage of perennials and reeds with artificial flowers.

The vineyard at Ickworth

The vineyard at Ickworth

The pond begins to overflow, as a little stream starts. It runs through part of the next door garden to a pipe under the road and into the next pond down the slope, which in turn flows into a bigger stream. This shows how the local ponds are connected and helps explain why the wildlife returned so quickly.

Geology and history

The structure of the pond, which is in a hamlet near Gislingham in Suffolk, told us quite a lot about the history. The likeliest origin is as a series of clay pits, which may well have been dug into an old stream bed. Once dug out, the farmer probably adapted the excavations to use as a moat and reservoir.

The pond bottom, we discovered as soon as we started the work, is a thick, hard layer of bluish-white clay mixed with chalk particles. Accounts of the geology of Suffolk confirm that this matches the description of a type of boulder clay, deposited by ice sheets, which is very common in East Anglia. A local construction engineer said the boulder clay stratum is at least 25 metres deep in our part of Suffolk, and is under most of the land between here and Ipswich, where it comes up against the London clay.

The pond is next to a farm cottage (ours) and a farmhouse, both of which are 16th century at the latest and may well be 15thcentury. There are also two listed barns in the old farmyard, both of which have been converted to houses in recent years, so the farm and its yard have now become four separate homes. Some archaeological research has been done on our cottage, and we are waiting for a detailed report that we hope will date the building.

The cottage unmodernised – no water, electricity or drains

During work on the cottage we went to great lengths to conserve and repair all the wattle and daub we found in the walls. The clay that made up most of the ancient daub was strikingly like that at the bottom of the pond. It seems clear from the composition that it must have been dug out of the pond at the time the houses were built, especially since the difficulty of transporting bulk material led people to use whatever was found on site. So that would date the pond to the 15th  or 16th century at the latest.

When the pond was eventually emptied and desilted, we found four distinct pits of varying sizes within the clay bottom: a small one in a shallow area, two rather larger ones in a slightly deeper place, and then a large excavation with steep clay sides which made up the narrowest and deepest part of the pond. For some reason, two of them were circled by low rings of clay, perhaps to keep rainwater back  while digging them out.

The exposed clay back wall of the cottage – attacked by woodpeckers looking for insects

Ours is the main pond, but it has arms at each end going at right angles into a neighbour’s garden, forming three sides of a square. One arm is just a shallow depression in the ground, no more than a ditch, which takes the overflow when the pond floods, but the other is deep and is still a proper pond. The previous owner of our property is convinced that this configuration shows that the pond was originally a moat, though the surface evidence of a fourth side, if there was one, has disappeared.

Two of the clay pits found during hand digging, filled now by rainwater.

There are said to be at least 2,000 moats in Suffolk and Norfolk. In his book Waterlog,  Roger Deakin says that there are more than 30 moats within a four mile radius of the church in the nearby village of Cotton. We are half way between Cotton and his village of Mellis. In Waterlog he writes:

Moats are now considered by historians like Oliver Rackham to have functioned as much as status symbols as anything else for the yeoman farmers who dug them. Mine was probably excavated when the house was built in the sixteenth century, and runs along the front and back of the house but not the sides. It had no defensive function except as a stock barrier. It would have yielded useful clay for building and formed a substantial reservoir.

The farmhouse near our pond is large and well built, and the family that lived there were probably yeoman farmers, well above the bottom of the social scale, according to a student of architectural history who included a note on the buildings in his dissertation.  So it seems plausible that the clay pits were dug to build the houses and then developed to become a status-symbol moat and reservoir.

A difficulty with the case for a moat is that neither of the present two timber and clay houses are within its boundaries. On the other hand, there are what look like old foundations of a building or a road on the side away from the present houses, and at one point these cross the pond.  The two ancient buildings now standing are on slightly higher and dryer ground, next to a still-prolific 5 metre deep well, so it is possible that the early inhabitants of the site moved their homes across the pond to a better site.

As Roger Deakin makes clear, some ancient moats were used to confine animals.  One practical configuration for an animal stockade would have been a three sided moat, perhaps with a fence at one end. So another possibility is a moat forming an enclosure without a building.

A plausible view, held by another neighbour, is that the U-shaped pond began as a bend in a stream that has since disappeared.  A ditch – now filled in by building work – seems to have run in from a field and, together with the pond, may have formed a meander in a stream. The presence of the clay pits is proof that the main part of the pond was artificially constructed, but there is no reason why the starting point should not have been an old stream bed. Stream or not, the deep and impermeable layer of boulder clay would have trapped water and would have been an obvious place for early inhabitants to look for springs and to dig for building clay, leaving rain, ground or stream water to fill the excavations, just like a worked-out modern gravel pit. It would not have taken much further effort to turn it into a status-symbol moat, whose configuration may have been dictated by an earlier stream bed.

It seems at least possible, if this has been a boggy site for millennia, that our pond dates to before the construction of the houses, perhaps to a much earlier settlement. Suffolk’s county archaeology department told us that a Saxon burial site was thought to be in the vicinity, which is one of the reasons why we were obliged as a condition of planning permission to hire a team of archaeologists (at our expense) to explore the ground around and under our cottage.

We found that the central area of the pond was relatively shallow and the bottom in that part was hard and lined with pounded gravel, sand and flint. It looked, when the silt had been cleared, like a road; an acquaintance who has worked on a number of farm ponds said that its purpose was to allow water wagons to be driven into the pond to be filled. It was also a hard bottom for cattle to stand on.

The owner of the farm, the cottage and the pond until the 1980s (who died some years ago) told a neighbour that it was last cleared in the 1930s, using shovels to load a horse and cart.  It took a whole summer. This explains why our desilting produced only a disappointing haul of objects:  mostly broken 20th century pottery, pieces of old motors, a bicycle seat, two well preserved leather boots of different sizes and the occasional small timber that could have come from a cart. It was the usual practice, our neighbour was told by the late farmer, to clear a farm pond twice a century, so the work on ours has been overdue since the ‘80s. References we found on the web suggested a typical large pond would silt up by more one centimetre a year. The depths of mud we found are not far out of line with that estimate.

Materials and costs

We used 50mmx150 mm   treated softwood in 1.5 metre lengths (which is short enough to give the impression of curvature from a distance when arranged along a bend. Straight sides would be unsightly).

We ordered it from a yard, Nelson Potter near Ipswich, which was able to re-treat it under pressure after cutting to length from their 3 metre stock, so there was no need for extra protection for the cut ends.

The treated timber was claimed to last for many years in water and to be non-toxic to wildlife.

Oak posts (recommended by a contractor) were too expensive. We used:

  • two 1.2 mx50 mm round pointed softwood stakes for each 1.5 m section
  • larger 1.8mx75 mm stakes for the deeper sides, driven in with a heavy fencing sledgehammer (a maul), after tapping in with a club hammer.
  • The treated stakes were so cheap that if they proved not strong enough they could easily be doubled up or have larger ones driven in alongside.

The hessian sandbags for the concrete were bought on Amazon. We used a dry mix of 5 sand and 1 gravel to one standard cement.

The following were the main costs, totalling £1,967:

Pumping £124                 Submersible pump from Screwfix £56, 22 metres of pipe £40, heavy duty extension cable £28).

Timber £825                     128 planks 1.5m x 50mmx150mm; 80x 1.2m x50 mm pointed round posts; 6 x 1.8m x 75mm ditto;  4 peeled    pine sleepers  2.4 mx50mmx100mm

 Digger £400                     One day’s hire with operator, after £100 discount because job was finished early.

 Concrete and gravel £470                Sand (3×1 ton bags), gravel (1x1ton bag for concrete, 3×1 ton bags for gravel path), 12 bags cement, 140 hessian sandbags

 Tools £45                            Lightweight aluminium shovel, fencing maul.

 Sundries £103                Including geotextile (14mx1m), plastic pipes and joints for repairing drains from gutters to pond, cuprinol.

Planning, trialling and surveying the pond

Dealing with wet silt

At the planning stage we discussed the following alternatives with contractors:

(1) Using a pump which would take silt directly to a disposal site, which would have to be a nearby field. This could be up to 250 metres away.   It would need the permission of the farmer. It would also destroy any remaining wildlife (though in fact there was very little in the pond by this stage.) It would have the advantage of keeping the existing size of the pond.   Along two sides of the pond the mud contained a lot of clay and we were dubious about whether this area could be pumped.  In fact, once our pond had dried and the mud consolidated, it was clear that pumping any of it would have been impossible.

(2) Excavating the whole pond with machinery and dumping the silt round the edges to shrink it, and building a timber revetement to hold the spoil back (which was also what we did ourselves). Oak was suggested for the posts, but this proved too expensive when we costed the job ourselves.

(3) Excavating with machinery and shrinking the pond in the same way as (2), while placing the spoil behind an artificial bank of geotextile, held under tension by wooden stakes inserted through pockets in the textile. The brand name of the textile proposed was Nicospan.  This method was due to be trialled on the Norfolk Broads for reinforcing river banks, and the Broads authority’s engineering department, which we contacted, gave us some positive views on it.

(4) In combination with any of the above, excavating a trench in the garden and using the earth dug out to build a bund round the trench, then filling the resulting it with some of the silt, covering with earth and leaving for a year to settle and drain before spreading it round the garden. This would be useful for very liquid silt.

(5) Using geotextiles to build a bund instead of a trench to contain liquid silt. The water would drain out through the textile. The silt would later be spread round the garden.

(6) Shrinking the pond by dumping the excavated silt around the shallow edges of the pond, then using logs from felled trees from the garden to contain the silt. This seemed ecologically very sound. However, the trees we needed to take down were ash, which rots very quickly in water and would disintegrate within a very few years. We weren’t convinced that this would really do a good enough job of containing the silt, and the contractor who proposed it could not show experience of work on ponds of this size.

(7) Shrinking the pond and building a wall entirely of sandbags filled with concrete to contain the silt.  When we costed sandbags, the saving in material costs was modest if there was a saving at all, and the labour involved much greater than building a timber containment. But we did use this method for two short sections where the bottom had a pronounced curve. It is also useful if the containment has to be high – with timber above 75 cm we would have needed to use much bigger stakes to hold it back. In general, we preferred the look of timber.

Trialling

There was a patch of ground at one end of the pond that flooded in winter, so we decided to use that as a trial area when the pond dried out in September 2009.

Late summer, no water, a metre of mud, 2009 trial dig in the distance

  • We dug out about a fifth of the pond’s area by hand and wheelbarrow, and dumped it on the wet land.
  •  Since the digging was not at the deep end of the pond, we removed no more than a tenth of the volume of mud it contained.
  • We used scrap timber to shore up the edge of the mud so that it did not slide back into the pond when it refilled, and waited to see how the spoil settled over the winter.
  • The operation raised the level of the patch of land by about a metre, but after two years of compaction and drying, the composted silt was down to perhaps a third of a metre deep and supported a thriving growth of grass and weeds, so it was a successful reclamation.

The test gave us a sharp lesson in what not to do:

  • When the pond dried out again two years later – a very wet summer intervened – we found our entire excavation of several hundred wheelbarrow loads of silt had filled in again.
  • The mud had flowed back from the rest of the pond, and this new deposit was much more liquid, and so harder to handle.
  • The lesson was that you cannot half clear a pond. You either have to finish the job in one season or build a barrier to protect the cleared area from the rest of the pond until the next season
  • Furthermore, partially clearing the pond seems to have released toxins that wiped out much of the remaining life in the pond. The smell of the gas rising from the silt was very unpleasant.
  • With perhaps 10 times as much mud again to take out, the experiment convinced us that we could not dump the rest of the spoil in the garden because of the sheer volume.
  •  With local farmers ruled out, that left only one place – round the edge of the pond. But we were reluctant at first to do that, because it meant a significant shrinkage of its area. We changed our minds when we realised that the old pond had been smaller, and that it had gradually expanded and shallowed as the banks crumbled under the assault of cows, ducks and frost over the years. Evidence for this was that the silt near the edges had a lot of yellow garden clay mixed into it.
  • The  main drawback of stacking silt round the margins of the pond is that if the mud is full of nutrients then they will gradually leach back into the water. Too much nutrient in a pond can cause algal blooms and retard other plant life. Experts such as the Suffolk Wildlife Trust advise against this. However, the expense of moving the mud elsewhere and the impossibility of finding space  for all of  it in the rest of the garden left the margins of the pond as the only practical disposal site.

Looking towards the deep end – 1.3 metres of mud

We needed to be sure that there was nothing too unpleasant in the mud:

  • The black surface went brown in an hour after it had been removed from the pond, as the oxygen got to it for the first time since it had accumulated at the bottom.
  • By the following spring, it looked and smelled like good garden soil and some of the surplus was distributed on the vegetable patch, which thrived. That was a good enough test for us.

Surveying

We quantified the job, to see whether we could manage it ourselves:

  •  The length of the edges was measured with a cord calibrated with knots at 2 metre intervals. This produced an approximate plan, and an area of about 350 square metres.
  • Surveying the depth of mud was easy round the edges, using a 2 metre stick with notches at 10 cm intervals. In the middle, because it was impossible to get close, we used a very crude measure that gave a usable estimate of depth. So:
  1. We cut a 6 metre straight ash pole from a hedge, we calibrated the pole with notches, and then we probed for the bottom from the side while keeping the pole at as near a constant angle to the surface as we could.
  2.  We reproduced the angle of the pole to the surface on flat ground and measured the vertical distance to the point on the pole that the mud had reached. 
  3. We then cleaned the mud from the pole and did it again in another spot. 
  4. It sounds horribly unreliable. But after the pond was completely cleared of mud we could see that this crude method had been accurate to about 10 cms, which was good enough. The result: maximum mud depth 1.2 metres (it actually proved to be 1.3 metres), average depth 50- 60 cms and total volume of mud around 175 cubic metres.

The decision to reduce the size of the pond allowed 100 sq metres of mud to be left in place, with new spoil dumped on top.  Since the mud was much shallower round the edges, this reduced the total volume to be shifted by only 20 to 30 cubic metres, to around 150 cubic metres (these numbers are all rough estimates).

Trials showed that it was feasible to shift 1 to cubic 2 metres an hour by shovel (depending whether a wheelbarrow was needed).

 

Pond management and conservation policy and advice – sources

 There is plenty of information available on line about pond conservation and management. But you have to sift through much material about building small garden fish ponds to find advice relevant to an old farm pond and moat . This is what we found most useful:

Pond Conservation, at Oxford Brookes University

The best single source is a charity, Pond Conservation,  based at Oxford Brookes University, which is entirely dedicated to ponds. Their website is http://www.pondconservation.org.uk/

Among other projects Pond Conservation is encouraging the creation of brand new wildlife ponds under a scheme called the Million Ponds Project. Its advice on wildlife, management, surveying and constructing ponds is comprehensive, and it also has material on historic ponds and how to look after them. The focus is very much on the wildlife in ponds and how to preserve it.

They disapprove of dredging ponds just to deepen them or prevent them drying out in the summer, on the grounds that a pond that dries seasonally remains an excellent habitat and may contain creatures specially adapted to these conditions, and that deeper ponds may actually be a less diverse habitat.

This ignores one important issue for pond owners, which is that the amenity value of  drying ponds with deep mud is very low. They are unsightly and smelly for months on end in the summer and autumn, and certain sorts of deep mud are dangerous. Yet for many people, the pond is the main feature of  the garden.  We do not think that managing for minimum disturbance to promote the wildlife should always be the top priority.

As explained in another post, our pond had a long history of intensive  management as a farm pond, and probably before that as a moat. We had good word of mouth reasons to think that it had been cleared twice a century in the past, and it was no doubt repopulated by wildlife after each clearance, perhaps going through several phases as different creatures moved in while it gradually silted again.    There are many other ponds in the neighbourhood from which creatures could migrate, the nearest less than 100 metres way,  and each is at a different stage of  its life so that, taking our hamlet as a whole, there  is a wide spread of pond habitat and creatures. We suspect the wildlife will fight its way back in, whatever we do, and that that has been true for generations of pond clearance.  Frankly, the alternative to clearing the pond would have been to fill it in to remove a summer and autumn eyesore (which one of the contractors advised was much the cheapest solution.) So we decided to  do what the farmers had always done, clean it completely, and wait for the wildlife to come back.

Suffolk Wildlife Trust

This organisation covers a wide range of issues, and does not ignore ponds . The website is http://www.suffolkwildlifetrust.org

It has useful detail about managing and restoring ponds.  The trust advises against encouraging ducks because they can deter other wildlife by muddying the water, constantly stirring silt, and depositing too many nutrients with their own waste. The trust is similarly negative about fish in ponds.

These documents have useful advice:

Pond creation
Ponds -New Zealand Pygmyweed
Ponds and ducks
Ponds and fish
Ponds and algae
Pond restoration & management

British Trust for Conservation Volunteers (BTCV)

Publishes an excellent manual, Waterways and Wetlands, a practical handbook, by Alan Brooks and Elizabeth Agate, which covers much more than ponds but contains very useful technical advice that applies to large ponds. Available from the BTCV or on Amazon. One bit of advice we ignored: it says don’t drive wooden stakes into clay bottoms. However, we assumed this meant puddled clay in canals and artificial ponds. Our clay bottom is a natural deposit and appears to be several feet thick in places, if not more. The BTCV website is:

http://www2.btcv.org.uk/

 The Wildlife Trusts

Umbrella body for 47wildlife trusts. Website:

http://www.wildlifetrusts.org/

The Wildlife Pond Handbook,  by Louise Bardsley with a foreword by Charlie Dimmock, published under the Wildlife Trusts logo by Connaught. Very useful for for learning about pond wildlife and plants, less so  for practical information about how to reclaim  an old pond.

Norfolk Broads Authority

We contacted the engineering department who gave helpful advice on using geotextiles in revetements built to support banks. We didn’t use textiles as the main barrier, in the end, but not because of their advice. Website:

http://www.broads-authority.gov.uk