Ponds and Water at Alvecote Wood
Broad-backed chaser dragonfly at new pond
There is a lot of water at Alvecote Wood - groundwater, standing surface water, drainage ditches, existing and new ponds, and an old well.
This section of the web site provides information about water sources and also about the developent of the wet habitats at Alvecote Wood.
What we already had
Alvecote Wood had a single pond marked on the map, but this is no longer a pond, being more a puddle in an old pit close to the road on the western boundary. Another pond was present lower down in the Wood. This had been dug about 18 years ago, fed by the drainage ditch on the north of the wood. This pond had largely silted up, the process being helped by a dense growth of sallow, and there remained a small pond which was nevertheless a valuable wildlife habitat.
As well as ponds, there was a lot of waterlogging and standing water in winter on the site. The large clearing had a large damp area, evident from the vegetation, which in summer was damp, but in winter had large areas of standing water, which could not drain away through the heavy clay subsoil. Although a valuable habitat in its own right, and we were keen to preserve it, it was also a problem for two reasons: First, the waterlogging severely limited the ability to move machinery around the site; second, the waterlogging appeared to be extending towards the south west of the site, and we believe two or more mature oak trees have probably died because of this.
We were keen to manage the water on the site by creating new ponds in the waterlogged area in the main clearing, and dredging and restoring the existing woodland pond. This would extend the pond habitat on site. We also needed to manage the waterlogging so that trees no longer died as a result of waterlogged roots, and to allow machinery to access the site, but also maintaining as much as possible of the wet habitat within the clearing.
As well as the ponds and wet area, we had a drainage ditch on the north boundary of the site into which flowed drainage from the adjoining horse stud and arable fields across the road, eventually flowing into the Coventry Canal just beyond the eastern tip of the site. This ditch zig-zags across the wood, with a single railway sleeper bridge, making it difficult to access the lower part of the wood on foot, let alone with either a brush-cutter or any kind of vehicle.
Upper ponds
Starting excavation for new upper ponds
The first ponds that were created were done in conjunction with development of the access road and new building. Drainage for the building roof was routed to a new pond. An overflow pipe was then inserted under the internal access track into two further ponds dug in a small part of the area currently known to be waterlogged in winter.
Lining these ponds proved unneccessary as the heavy clay soil and high level of groundwater meant the ponds filled spontaneously even in dry weather. The upper ponds were completed in late 2008.
In early 2009 it was apparent that the waterlogging problem needed further management, and as part of this project, the pond profiles were adjusted and drainage trenches were created to receive land drainage water from across the clearing, where waterlogging was continuing to put mature trees in jeopardy.
The clearing, with a damp grassland area and
new upper ponds just visible in the foreground
During May 2009 we populated these ponds with native local wild pond plants. We have also sown wildflower and grass mix over the areas of soil excavated as part of our pond digging and drainage work, and in adjacent prepared parts of the clearing to create wildflower meadow habitat.
Lower ponds
In early 2009, the existing lower pond had contracted to a fraction of its original area. We tackled this by felling a proportion of the sallow trees that were taking water from the pond. A small plantation of sallow was left, and some of the larger trees were cut down and the stumps moved to the edge of the new pond so that they could re-establish in a place where they would not take excessive water. The felled sallow saplings and twigs will be re-used on site for a variety of projects.
New lower ponds at Alvecote Wood
We decided that instead of one vast pond, we would create three inter-linked ponds. This would enable us to extend the area of water without disturbing the existing remaining small pond area and the wildlife that it already contained. In addition, this would create several areas for silt deposition, so clear water would flow back into the drainage ditch. The lower end of the existing pond was built up to raise the water level (by about 50mm to compensate for the extremely low water level in summer), and the exit channel was made more defined to allow flow of clean water back into the drainage ditch rather than a general outpouring over the adjacent land, which was compromising more mature oaks in the vicinity.
Ponds in Betty's Wood
Five new ponds were dug in early 2011 at the lower end of Betty's Wood, our newly-acquired former arable field. Of these, four have filled spontaneously with water and remain full despite the severe drought conditions. One has not filled, and will require further work in the winter of 2011. These are being allowed to colonise naturally, and we have already seen plants, dragonflies, insects and birds moving in.
Ditches and Bridges
Existing ditches on the site were becoming silted up and blocked by fallen trees, branches, leaf and twig debris. In early 2009 we commenced the process of clearing these so that water could flow along the channels and on into the canal, without causing flooding within the wood. Very little of the water flowing down these ditches originates in Alvecote Wood, the majority flowing in via drainage from adjacent land.
Getting around on site was limited by the absence of a bridge on one part of the drainage ditch, and although there was a railway-sleeper bridge across one arm of the ditch, this was not sufficiently strong to take a vehicle. During 2009 we plan to remove this bridge and replace it with a culvert to allow water to pass freely down the ditch, and to provide a strong platform across which vehicles can pass. The existing railway sleepers will be used to produce a pedestrian bridge further down, allowing access on foot carrying equipment to the lower part of the woods.
Drainage
Digging drainage trench - note dead tree
adjacent to trench
Installation of land drainage was a priority for the site for the maintenance of the trees, as well as to permit access by vehicles beyond the clearing. Some drainage of the entrance to the building where water tended to collect was also required. An existing land drain was present in the waterlogged area of the clearing, but was no longer functioning correctly although water was still flowing through it into the ditch at the north side of the property.
Drainage ditches were therefore dug from an area at the south west of the clearing where it was clear that waterlogging was compromising mature oak trees, to join with the ponds near the new building. Other small ditches were dug to receive drainage from the building and from the access road, and from the waterlogged area at the entrance to the more heavily-wooded part of the site, hopefully solving another problem with waterlogging preventing management access.
This drainage has made a very significant difference to ease of access to the site as well producing a reduction in waterlogging at the south west of the site. The majority of the large wet area in the centre of the main clearing has been left untouched as a damp habitat.
We hope that this drainage will improve the site, reduce damage to trees, increase accessibility and preserve existing damp grassland habitat.