Existing Condition of the Pond

Only 28.87 acres of open water remain in the pond as the incessant deposition leads to the succession towards dry land. The deposited material becomes progressively older and drier towards the northern end of the former pond. The older deposits are sufficiently stable to withstand the weight of machinery and have been planted over with trees. The younger deposits are more boggy and marsh like in character. These have become overgrown with alder and more especially willow. Great swathes of reed mace at the mouth of the feeder stream slow down the waters entering the pond and promote further accumulation and deposition of silt resulting in further loss of open water and reduction in the overall length.

The fringe of reed mace extends almost the whole way along the banks, in some places reaching up to several meters wide. The close-packed stems create the still conditions to allow deposition, with the result that the pond is becoming steadily narrower as its banks are extending inwards towards the centre - as further deposition occurs, so the depth of the water decreases and the swathes of reeds grows wider. There is a periodic programme of cutting back the rushes in order to control the loss of open water, but the sheer scale of the pond means that this operation has little impact.

There is a similar picture in the south-eastern arm of the pond, where large areas of alder and willow carr have developed on pond deposits. Leaf mould and further deposits continue to build up and so the area of the pond continues its progression towards dry land. In this area the problem is compounded by the vast areas of water-lilies that exist, which further slow the water allowing deposition and whose leaves annually contribute to the build up of sediment.

As silt has been deposited over the centuries, so the depth of the water has also been diminishing. Much of the remaining area of open water is covered by only a thin veneer of water, no more than a few inches deep. This becomes startlingly apparent when the water is drained down as the photographs in figure 19 demonstrate. The pond is so congested with silt that from some viewpoints it is not instantly obvious that the water has been removed. 

In addition to the effect upon the appearance of the lake, the siltation has other impacts. For instance, in mid-summer there is a massive algal bloom across most of the open water, which creates a dense covering across the surface. This is likely to be caused by a combination of high nitrate levels and insufficient water depth. The shallow water warms up quickly creating ideal conditions for the development of filamentous algae on the pond bed, which floats to the surface to form a dense blanket preventing light from penetrating to the lower levels. Over the long term this has a considerable impact upon water quality and is damaging to the overall ecology of the lake.

The siltation of the pond is a major concern. Some dredging work was carried out in the summer of 1939, as shown on the photographs below. But there are no records to indicate the amount of silt that was removed. Some recent attempts have been made, including a sudden drain-down in the hope that some of the silt would be dislodged in the rush of escaping water. This experiment resulted in a substantial build up of silt around the outflow but little silt actually left the pond. A seemingly more drastic measure carried out by the current owner’s father employed the use of explosives in an attempt to dislodge the more solidified areas of silt at the northern end. This, however, also resulted in failure, as the silt was blown vertically into the air - landing in the same hole that had been created by the explosion!

A trial excavation carried out in 1996 revealed that the silt was up to 2.2m deep at the southern end of the lake, close to the dam (see picture below) . The excavated material, which was found to be quite firm, was spread in an area of the adjoining Filleys Platt. In the intervening 4 years, the deposits have dried out and shrunk back a certain amount (20%) and become grown over by grass with considerable areas of willow and birch scrub also becoming established.

Silt is up to 2.2m deep at the southern end of the lake

Ecological Value

The lake is the premier habitat in the locality. Its importance derives from the extensive body of open water and the progression of habitats found around its margins. It attracts a wide variety of wildfowl, both to over-winter and to breed, though few of these are diving species, and supports a notably large Heronry comprising some 15 breeding pairs. Its margins are also host to a large number of dragonfly species, reptiles and amphibians. Its wildlife value is recognised by its being designated as a Site of Nature Conservation Importance in the Local Plan.

The Threat to the Pond

The unique value of the pond must surely be the sheer scale of the expanse of open water, which was at one time reputed to be the largest artificial water-body in southern England. But, as the silt deposits continue to accumulate, so more and more of the open water is being lost. Furthermore, because so much of the surviving area of the pond is now only covered by a limited depth of water, little further build up is needed before large areas of the deposits break the surface of the water and form a pattern of small islands in the pond. This effect can already be seen in certain areas, especially close to the edges.

If action is not taken soon then there is a very real danger that the pond will rapidly decline, becoming ever shorter and narrower, until eventually it will disappear. There is indisputable evidence that this process is already taking place and may even be accelerating and the attempts of the current owners to check the spread of the reeds are of limited impact given the scale of the problem. 

The restoration of the pond is, therefore, a primary objective which would not only restore the historical setting of the Grade II* listed Castle, but which would greatly improve its overall appearance, and enhance its nature conservation value.

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