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.
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.
At least 30cm more water needed to reach the top of the revetement.
The rains begin, making up for the drought.
Still filling – 12 cm in 3 weeks. About 30 cm below old springtime level.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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!
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.
The ponds are connected, which helps explain why some of the wildlife came back so quickly.
A quiet and very wet month.
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.