Small ponds can be damaged by fly-tipping and pollution. They can become silted up, cease to hold water due to damaged linings, or dry out due to lack of maintenance of the water supply system. Small ponds in villages and urban areas are often artificial features, which require management in order to sustain them. Other ponds in woods or semi-natural habitats may require less intervention.
Large ponds in urban areas often suffer from eutrophication, which is a raising of the nutrient level. This can be caused by the nutrient load of the water supply, by silting of the pond, or by unsustainable populations of fish and ducks. These ponds support few marginal or aquatic plants. Major works are needed to restore such ponds and lakes. The London Lakes Project Report describes the transformation of some of London’s lakes by improving the quality of the water supply, aeration, planting and control of fish and waterfowl.
Pond succession
The need for management work on ponds should be carefully considered. neglect in the form of rubbish, litter and pollution needs tackling, but ‘overgrown’ ponds and streams are often valuable habitats as they are. Ponds are dynamic habitats which, over the years, silt up as marginal vegetation spreads from the edges. A small shallow pond may change in a couple of decades from open water, to marsh, scrub and then damp woodland. For wildlife, all of these stages have value. Clearing an overgrown, shady, marshy area to create an pond with mainly open water may not be the best option for wildlife. Ideally, where space permits, a range of pond habitats with open water, marsh, scrub and damp woodland, linked with a ‘buffer zone’ of scrub, long grass and other cover should be the aim.
Habitat fragility
Ponds are fragile habitats, which are easily spoiled by excessive trampling or clearance. Damp soils and plants of wet places are quickly damaged by trampling, or by being covered with silt or plants dug from a pond. Excessive disturbance or removal of silt may completely destroy a population of invertebrates, or disturb hibernating amphibians. Management work should be limited to defined zones of the pond or stream, with areas managed in rotation over a period of years. Where clearance is required to ‘turn back’ the succession, clear a maximum of one third of the pond in any one year.
Working season
Clearance or other management work should only be carried out in the period from September to November. This avoids the breeding and hibernating seasons, minimising disturbance to wildlife. Problems of algal blooms from disturbance of the water and bottom sediments are also avoided at this time of year. The weather is usually mild, with lower water levels and dry bank conditions making it a pleasant time of year for working.
Safety guidelines
Observe the general safety guidelines in Health and safety. In particular, take care with the following:
Before agreeing to do the project, assess the pond, stream or ditch and its surroundings to check that the site is safe. Contact the relevant agency (Environment Agency, Scottish Environment Protection Agency, Department of the Environment for northern Ireland) if there is any evidence of pollution.
Weil’s disease is a bacterial infection carried in rat urine, which is present in ponds and other wet places. To reduce the risk of infection, protect any cuts or grazes with waterproof plasters, and wash hands in hot soapy water before eating, drinking or smoking.
Mud, submerged debris and variable bottom conditions make all ponds and ditches a potential hazard. Check bottom conditions with a cane or similar before allowing people to wade in. Always have some people on the bank, with ropes, poles or grab lines to hand. Take great care if using thigh waders, and move slowly and carefully. Chest waders should not be used. Lifejackets should be worn if working from a punt.
Avoid working on slippery, muddy banks.
Consultation
At an early stage, consult with local residents, the local authority, and with the local wildlife trust. Try and find out about the history of the pond and how it looked in previous decades. The wildlife trust may already have some records of the wildlife value of the pond, or be able to give assistance with survey work. Where flowing water is involved, the Environment Agency, or equivalent in Scotland or northern Ireland, should be consulted.
Management plan
Through consultation, draw up a management plan for the pond. This should include the following information:
- ownership of the pond
- any historical details
- responsibility for management
- sketch map
- buffer zones or undisturbed areas
- new planting of pond, marginal or bankside plants
- dead wood, habitat piles etc.
- access, which may include paths, dipping platforms, steps
- maintenance plan for the next five years, showing zones for clearance, cutting, planting or other work.
Removing rubbish
Before organising a working party, check the pond area for the feasibility and safety of a clearance operation. Small items of rubbish on the banks and edges should be removable by hand, but larger items will need ropes or winches. Great care must be taken in moving heavy items in muddy, slippery conditions. If there are signs of pollution or of toxic materials, the Environment Agency (or equivalent in Scotland or northern Ireland) should be contacted. Volunteers should not handle toxic materials or work in polluted water.
Ensure there are sufficient pairs of heavy-duty gloves for everyone taking part. Plan where the rubbish will be put once it is removed. If there is suitable access for a vehicle, order sufficient skips. Larger metal items may be worth gathering separately for collection. Thick plastic sacks should be obtainable free of charge from the environmental health department. Ensure that the skips or sacks are removed to a disposal site at the end of the day, to avoid the possibility of vandals tipping rubbish back onto the site.
Clearance of rubbish that involves disturbing the pond sediments should be done in autumn, to avoid disruption to wildlife. Leave large items on the bank to allow water, mud and organisms to drain back into the pond. Rinse out containers to remove the sediments they contain. Use scaffold planks or similar to avoid trampling of fragile damp soils.
Removing silt
Digging out a silted pond should only be done after careful consideration of other options. If there is a space to dig another new pond nearby, this will result in a more valuable range of habitats.
If digging out is the only option, consider hiring a machine and operator. This is likely to be much quicker and safer than doing it by hand. Tracked machines with a long reach minimise ground damage, and temporary trackways can be used to support machines on soft ground. Enquire around other conservation organisations for contractors experienced in this type of work. Ensure that the operator is well briefed, and that the site manager or project leader stays on site throughout to supervise the work. Consult locally and publicise the project before the machine starts work, to avoid misunderstandings about what the machine is doing!
If working by hand, you will need scaffold planks for barrow runs, barrows, shovels, spades and buckets. If possible, organise a circular route for pushing the barrows to get the job done efficiently. Tip the silt direct into a skip if possible, to avoid handling it more than once. Alternatively, mound it up or spread it on an area of low conservation value.
How much silt to remove?
Completely removing all the silt, down to the liner, layer of puddled clay or natural bottom, will also remove all the organisms contained. On the other hand, removing small amounts will mean the work will have to be repeated every couple of years, with repeated disturbance to the pond and its surrounds. Take advice locally, but in general clear about one-third every five years or so, leaving about two-thirds of the pond untouched.
Managing emergent vegetation
Ponds which are used mainly for amenity and educational use are best maintained at a mid-stage in their succession. A fringing ring of emergent and marginal vegetation is a valuable habitat for plants and animals, as well as looking attractive, and helping protect the pond from human disturbance. Too much vegetation will result in the pond growing over completely, with a loss of open water. If the pond bottom drops steeply from a marginal shelf, the system may be self-regulating, as marginal plants cannot grow in water over about 600mm deep. Where the pond bottom slopes gently into deeper water, some clearance or cutting of vegetation may be necessary. There are two general approaches, either of which may be suitable.
- Divide the pond into sections, and each year clear some sections from the bank down into deeper water. This will provide a range of habitats and age structures of vegetation. Choose a rotation which suits the size of the pond and the labour available. The diagram below shows the growth at the end of a four year rotation.
- Alternatively, plan to clear the ‘invading front’ every other year, or as necessary, to keep the vegetation cover to roughly the same area. This will not provide the variety of age structure of the first method, but may be best where it is important to avoid opening up access to the water ’s edge. (See diagram below.)
For more details on different types of pond vegetation, see page 100 below.
Managing bankside vegetation
The most important feature is to plant or retain a ‘buffer zone’ of long grass, shrubs, hedgerow or copse which reaches to the water ’s edge, and is preferably free from human disturbance. Where possible, this should link with a hedgerow, woodland, rough grassland, railway bank or other area of land which will greatly increase the pond’s value for wildlife, by providing habitat for amphibians, invertebrates, birds and other organisms which will use the pond. Where the buffer zone meets the pond, fence off this section, or encourage brambles, nettles and other plants which will discourage human interference.
Within the buffer zone, plenty of cover should be encouraged. Plant shrubs and trees for coppicing. Where there is sufficient space, plant trees for growing to full size. Any dead wood, piles of old sawn timber, prunings, stones or other building material will provide cover and hibernation sites. Pieces of sheet material such as plywood or corrugated iron, left lying on the ground, will be used as cover by amphibians, reptiles or other organisms. To avoid these materials looking unsightly, plant screening shrubs, or stack the material in a semblance of order. A neat wooden structure built like a compost container can hide all sorts of materials which will provide habitat.
Avoid cutting down trees or shrubs, unless it is necessary to provide access for pond-dipping, or to increase sunlight to the pond. Only cut on the southern side, and coppice or pollard trees if possible, rather than removing them altogether. Dead trees and old stumps are very valuable habitats, so only remove dead branches or trunks which may be a danger to the public. Leave trunks and cut timber on the site.
Ponds used for pond-dipping will need sufficient area to accommodate groups of children. Mow paths and a meeting area to encourage hard-wearing turf, and allow other areas of grass to grow longer, and discourage trampling. Access for pond dipping is discussed below.
Brambles, nettles, bindweed, thistles and other plants are valuable for wildlife, but should be kept in check to stop them smothering other plants and preventing access. nettles and some thistles can be dug up quite easily. Brambles, creeping thistle and bindweed are very difficult to dig up, and are best treated individually with a glyphosate herbicide, obtainable from garden centres.
Follow the manufacturer’s instructions, and take great care not to spray into water. A small hand-held spray used on a still day allows accurate spot treatment.
Some ponds and other waterways support populations of particularly aggressive introduced plants, which spread rapidly and are hard to remove. Prevention of spread of two of these species, Japanese knotweed and giant hogweed, are required under the Wildlife and Countryside Act 1981. Himalayan balsam is another rapid spreader which needs controlling.
Japanese knotweed (Polygonum cuspidatum) is a perennial with stiff bamboo-like stems and very tough rhizomes, which can grow through concrete and tarmac. Tiny fragments of rhizome can produce new plants, so dispersal by water or contaminated topsoil is easy. The best method of control is to spray with glyphosate in May, and then spray the regrowth in July or August. Spot treatment in following years may also be necessary. Cutting or digging out as a method of control is not recommended, as this is likely only to cause further spread of the plant.
Giant hogweed (Heracleum mantegazzianum) is a biennial, flowering and seeding in its second year. If it is cut down before it produces seed, it will survive in to a third or subsequent season, attempting to flower each year. The sap contains a toxic chemical which sensitises the skin and leads to severe blistering when exposed to sunlight. This reaction can recur for many years. The only effective method of control is to spray with glyphosate when the plants are about 1m high, in April or May. Seeds remain viable in the soil for seven years or more, so it is advisable to establish a dense grass sward as soon as possible to suppress germination. Mow the grass to encourage a dense sward, and spot treat any hogweed seedlings that appear.
Himalayan balsam (Impatiens glandulifera) is an annual, which grows to about 2m, with purplish-pink slipper shaped flowers from June to August. The mature seed pods explode when touched, scattering the seed. Control before the seed pods form. Hand pulling is possible in light soils, and cutting at ground level is also effective. Cutting above the lowest node only encourages the plant to regrow. Remove all cut growth for composting or burning.
