Woodcote: The Greenmoor Ponds
by Karen Woolley*
Historical background
The two ponds at Greenmoor, Woodcote (SU646812) cover an area of 1.635 acres [0.662 ha]. They are on registered common land and are situated at the second highest point of the South Oxfordshire Chilterns. The contrasting nature of the two ponds – the relatively shallow and very well vegetated Upper Pond and the much deeper, relatively sparsely vegetated Lower Pond, which is more heavily shaded by trees – adds to the value of the site both in terms of its visual appeal and ecological interest.
The Upper Pond
The name Greenmoor (also spelt Greenmore) is derived from Greenmere, meaning a green pond or pool, and is first mentioned in a document of 1109 when Henry I confirmed the possessions of Eynsham Abbey. The ponds are shown on a map of 1818 and were identified as public watering places in the Enclosure Award of 1853, and on an early (undated) map were named as ‘Sheep Wash Ponds’. The ponds were situated on the edge of Woodcote Common and people from outlying settlements would water their livestock at the ponds before entering the common through a gate at that end.
There is a mapped earthwork enclosure in nearby Friarhampstead Wood, less than 1 km away from the ponds. Representatives from English Heritage have recently visited this site and suggested that it may be Romano-British in date. As there are no other sources of water in the vicinity, it is considered that the Greenmoor Ponds may well have been used as a water source at that time.
The larger (lower) pond was still used as the main source of water for local people until the mid-1920s and the old well head can still be seen at the north-west end of the pond. English Heritage considers the Greenmoor Ponds to be of significant historical importance and accordingly has stated its intention to designate them a Scheduled Ancient Monument.
The Lower Pond circa 2000
Ecological background
Both the Parish Council and local people have always valued the Greenmoor Ponds for their wildlife, and in 1990 and 2000 Pond Action undertook a survey of the ponds and judged them to be ecologically important. The survey (undertaken by Jeremy Biggs of Pond Action) indicated that ‘both ponds have a very high conservation value’ and a rich fauna, including nine nationally scarce species. Some of the species recorded include water beetles, frogs, toads, and smooth, palmate and great crested newts (the latter were not recorded in the 2000 survey) and a wide range of plants. The site was considered to be within the top 15% of ponds identified by the National Pond Survey in terms of species richness.
As a result of the 2000 Woodcote Village Appraisal, the Woodcote Conservation Group (WCG) was established – mainly to manage the Greenmoor Ponds – and initiated discussions with Thames Water (which owns adjacent woodland) to manage the whole site as a wildlife area. The WCG (in association with the Parish Council) also commissioned a full ecological survey of the site and has since compiled a three-year management plan, to which it is now working.
Thames Water has not yet made a decision about the future of its area of woodland, but if it agrees to these proposals English Nature and Oxfordshire County Council have agreed that the whole site should be designated a Local Nature Reserve, due to its diversity of habitat. The Greenmoor Ponds are therefore not only of historical importance but also have considerable ecological importance.
Hydrology background
The hydrology of the Greenmoor site is not simple. The two ponds are physically close together but exist in a hydrological sense as two more or less separate entities. Any permanent changes in land use on site or within the catchment of either pond, or disturbances such as one-off excavation works or similar, could have an impact on water movements into, out of or through the site.
There have been no major changes in the condition of the Upper Pond (which has a separate and independent water catchment to the Lower Pond) but unfortunately over the past four years the level of water in the Lower Pond has been dropping steadily and is now some two metres lower than its original level. There will always be seasonal cyclic changes caused by variations in precipitation, with lower water levels to be expected after dry summers or winters, but the dramatic drop in level of the Lower Pond cannot be the result of any such seasonal changes.
The Lower Pond receives water from several sources. There is a series of springs at the western end of the pond, which were possibly the source of water for the well (now capped). The pond also receives direct precipitation and some run-off from the surrounding land, although this is limited because the catchment area is small. Evidence also suggests that there is sub-surface flow into the eastern end of the pond from the north. This flow enters the pond by seepage through either the upper part of the bank and/or at a lower level. The precise route of this water is not known. While these sources continued undiminished the pond remained full, with only a relatively small drop in water level during the summer months. However, the loss or reduction of one or more of these sources would probably cause the water level to drop. Damage to the pond lining could also cause the level to drop, if the rate of water flow into the pond were not sufficient to compensate for the rate of out flow.
The start of the drop in water level coincided with ground works close to the pond to bury electricity cables formerly located above and along the length of the pond, but this work has now been ruled out as the cause of any possible alteration to water flow into the pond. Recent and careful excavation work around the cables has indicated that the surrounding area – down to a level of approximately two metres – is completely dry.
Over the last year, under the auspices of Woodcote Parish Council and Ponds for People Oxfordshire, investigations have been carried out in an attempt to identify the actual cause(s) of the dropping water level in the Lower Pond. This information has been used to develop and implement a plan to reverse this loss of water and restore, and, where opportunity allows, improve the Lower Pond for people and wildlife. If restoration work had gone ahead without this survey, there would have been the risk that large amounts of public resources could have been expended without the underlying problem being resolved, and further potential problems created.
* This article first appeared in SOAG Bulletin, No. 60 (2005), and is reproduced here with the kind permission of the editor. The author is a committee member of both SOAG and the Woodcote Conservation Group, and coordinates the Greenmoor Ponds restoration project. For further information on SOAG (the South Oxfordshire Archaeological Group) visit www.soagarch.org.uk.