Bowlhead Green Pond (High Stilwells) renovation 2014-2016

I originally believed that the pond was one of the "High Stilwells", but after a lot of investigation I now believe this to be man-made and dating from the early 1800s, and probably from a lot earlier. The feed is mainly via water run-off from the village roads where there are a number of springs (Style-wells?) that sprout up in wet weather. The ground water also seeps up from underneath when the ground is saturated. The location of the pond is important. The pond was a central collection point for spring and rain water, being the lowest "common land" in the village. From the pond the lie of the land drops sharply down, over private fields, towards the lakes in the valley. The pond was probably dug out for two reasons. Firstly, as a storage area to provide water all year round to feed stock (mainly sheep and horses) in an area that would probably have been dry during normal summers. Secondly, the underlying geology of the area is Greensand which typically has a 25-30% clay content. The residue from the excavated pond would have made good brick material. A clue is that the field above and behind the pond is called Kiln Field on the old tithe maps. The pond lining is clay puddle, which would not be a natural occurrence.

In 2014 the pond and surrounding area had got into a bad state. The pond severely flooded in the winter of 2013/14 and the lane alongside (one of the only the two decent access roads to Bowlhead Green) was closed for 3 months. I decided that the pond needed renovation, if only because it was the last visible link with "Stilwell". The photographs above, taken from a drone, show the pond area in December 2014. It hadn't been a wet December and so there was little water in the pond as can be seen in the photographs. Normally, in any December, the pond would be full. The main reason the pond was not holding water was that a number of trees had breached the clay-puddle lining with their roots and the water had seeped into the very porous sand underneath. There were three "rogue" alder trees growing out the pond and the two large willows alongside the pond would have also caused problems with their roots. The willows had fallen down in the very wet winter of 2013-4 and been sawn up and left in place. This is evident in the lower picture above. All along the back of the pond was a very large spruce tree that had also fallen down in the winter floods. The trunk of this tree was completely covered in ivy which considerably increased its weight and wind resistance and caused it to fall in the winds. On the "green" alongside is a mature oak also in poor condition and being strangled by ivy. If you are wondering what the little black speck on the grass top right is, that is myself and the drone pilot.

Planning the renovation

The pond is within the Bowlhead Green conservation area. The local council (Waverley BC at Godalming) were approached and were very supportive of the project. Their permission was given to fell the alder trees, remove the lower limbs of the oak tree to raise the canopy, and to fell some other small trees on the back edges of the pond. The drainage into and out of the pond needed re-instating and Surrey County Council acted with commendable speed and cut new drainage ditches to prevent future flooding and cut a new feeder ditch to the pond, which was sorely needed. As of the autumn of 2015 the whole area around the pond had been cleared of unwanted trees and foliage, almost entirely single-handedly by me. The excavation of the silt and clay in the pond was too much for a few people with spades, and the laying of a permanent pond liner (to replace clay puddle) is a specialist job. A specialist was engaged to do all this and a cost obtained. A grant was obtained from a Surrey countryside charity in February 2016 and the renovation was completed on 24th March. Whilst digging out the new pond the digger unexpectedly encountered ground water. This was after 8 days of no rain at all. To lay an artificial liner was now not possible as, during wet periods, the ground water would get underneath the liner and push it up, creating what the industry calls a "hippo" (needs no further explanation....). The decision was made by myself and the contractors to not line the pond and retain it simply as a 6 foot deep dew pond, and it will fill in wet weather and slowly drain away in dry weather. Heavy storms would cause a lot of water to flow into the pond. The cost was less than the grant obtained from the charity and the excess was returned to them.

The water level was monitored in 2016 and was stopping about 300mm short of the overflow ditch. It seemed that the clay strata was that distance below the overflow and above it was natural greensand and the rainwater was soaking away through this level. The experts were consulted and it was decided that it would, after all, be viable to clay-puddle the pond to create an impervious clay lining. A quote was obtained and the charity approached for another grant, which was approved in August 2017. The returning of the unused part of the previous grant was, we are sure, a good point in our favour and helped to secure the second grant. Clay puddling took place a few weeks later and the pond now fills to the overflow. To help the feed of rainwater from the road into the pond the main ditch was lined with a clever material called Concrete Canvas. The cost of this was included in the grant.

A montage of before and after photographs can be seen by clicking the link below-left. The link below-right has an AVI video of Bowlhead Green taken in December 2014 (a frosty morning). All but the first quarter of the video covers the area that would have been High Stilwells. The video starts and finishes with the pond area bottom left.

Martin Stilwell, December 2017