Specialists in Water Management for Landscapes, Fisheries, Leisure and Conservation
News
October 2004
Warning as killer weeds endanger our plant and water life
Foreign, water-borne weeds are already beginning to clog our rivers, lakes and ponds. As this invasion of pernicious and environmentally deadly flora reaches epidemic proportions, Brussels has banned the only known weed killer that can eradicate some of the worst offenders.
According to one of the country’s leading water management specialists, the banning of the chemical Diquat alginate will allow the spread of invasive weeds to such an extent that the balance of nature of our countryside and parks will come under threat, endangering the very existence of many species of our own indigenous plant and water life.
“We all have to act extremely quickly to get rid of these atrocities before existing stocks of Diquat alginate are exhausted.,” said John Colton, managing director of Kingcombe Aquacare, “These weeds are extremely hardy and their presence in our inland waters is now an extremely serious issue. They are not only destroying our environment, but are now beginning to have a negative effect on our water margins, fish and pond life. It’s just typical of EC bureaucrats to ban the only effective weapon we had in our fight to eradicate these foreign invaders from our island. I would ask anyone finding a colony of these weeds on their land to get them eradicated as best they can and as soon as they can.
“The first hurdle is to recognise an incursion of these weeds when you see one. To help in their identification, I would recommend anyone finding what they believe to be an invasive weed to visit our website at www.kingcombe.com which contains photographs and descriptions of the worst offenders and the best course of action to take in their destruction,” said Mr. Colton.
Sharing first place on the list of non-native, pernicious weeds are the Australian Swamp Stonecrop (Crassula helmsii) and the Japanese Knotweed (Fallopia japonica), followed closely by Giant Hogweed (Heracleum mantegazzianum) and Floating Pennywort (Hydrocotyle ranunculoides).
“Unfortunately, getting rid of them is not easy as each species has to be eradicated using different techniques,” continued Mr. Colton. “What will work for one can actually accelerate the continued spread of another!” he warned.
“As an example, the Australian Swamp Stonecrop, which was introduced from Tasmania as an “oxygenating plant” in 1927, must be controlled by chemical rather than mechanical means. Any fragments resulting from cutting or tearing can re-grow and worse, spread the infestation downstream. Fragments as small as one node (5mm) can re-grow. Special herbicides are the only answer.
“Unfortunately, due to EEC legislation, effective herbicides will soon be unavailable for tackling this plant, so it is important to deal with the problem now, while we still have the means to do so,” he concluded.
Japanese Knotweed is rapidly colonising river banks and areas of waste land forming dense stands up to 3 metres high in summer, severely impeding access to river banks and shading out native species, leaving banks bare and liable to erosion in winter. Then, it survives in the form of rhizomes which grow rapidly and have been known to grow through rock, tarmac and concrete, damaging embankments and structures.
“Killing it by mechanical means just does not work with this weed and will certainly assist its spread as even the smallest surviving fragments have the ability to re-grow. Spraying with the chemical Glyphosate will work, but further applications will almost certainly be necessary.
Another alien weed to watch out for is the Giant Hogweed. Its sap contains a toxic chemical which sensitises the skin and can lead to blistering of the skin when exposed to sunlight. Once a plant has produced seeds, it can be assumed they will be present in the surrounding area - and it is believed they can remain viable for up to 15 years. A chemical treatment is available, but the timing of application is critical if it is going to be effective.
Floating Pennywort was introduced into the UK from North America as a plant for tropical aquaria. It roots in the margins of slow-moving waters and lakes and forms dense mats of vegetation. It has been recorded as growing up to 20cm per day! This weed has proved particularly difficult to control and can cover the surface of waters interfering with the ecology and amenity value of any water it may infest.
Cutting Floating Pennywort is only a short-term solution as it can grow back to its former bulk extremely rapidly. There is a chemical solution, but the timing of its application is critical to any success. However, any application of herbicides to water can only take place with prior approval from the Environment Agency. Kingcombe Aquacare arranges all the necessary consent on behalf of their clients. The best solution is to remove any stands of this weed as soon as they are spotted and before it has had a chance to fully establish itself.
Makeover for Barbican lakes
It is not generally appreciated that the Barbican complex, in the City of London, includes 2.5 acres of lakes and water features. The lake had been installed as part of the original design, which was a landmark building for the late 1960 and early 1970s. However the mechanical and electrical infrastructure - which had been installed at that time to manage the water, including the pumps, fountains, waterfalls etc., - was becoming increasingly expensive to maintain and operate, and water quality was not meeting the expectations of the residents or visitors.
Water management specialists Kingcombe Aquacare Ltd were invited, in competition with several other companies, to produce a turnkey solution for the restoration of the water features, and in particular to improve the aesthetic and chemical quality of the water, whilst reducing operating costs.
Following a design and cost appraisal by the Corporation of London, Kingcombe were awarded the contract. Their proposals provided the most complete solutions to the problems as perceived and, most importantly, offered significant year-on-year cost savings.
The company’s solution involved draining down and cleaning out the accumulated organic debris from the ponds, followed by the installation of an array of fountains and flow-makers designed to capture the character of the original 1960s’ design, but using modern technology and small individual components to reduce the maintenance requirements and thus minimise the whole-life service cost.
The old brick weirs were also modified to concentrate the available water flow. This significantly added to the visual amenity but also produced considerable environmental benefits by increasing the aeration of the water for no extra cost.
Chris Keech, Kingcombe Aquacare’s construction director and the man who masterminded the project, said no two waters are ever quite the same. “The Barbican lakes presented us with very real challenges. Developing an environmentally sound solution within such an enclosed man-made feature required considerable ingenuity combined with some basic principles of water management.
“Essentially our plan was to introduce sufficient oxygen into the water to encourage a natural biodegradation of organic material, but in a way which complemented this high-profile site.”
Aquapilz aerators and flow makers now ensure a constant mixing of the water. Each group of equipment is individually controlled for flexibility of use and, most importantly, if any one unit fails it can be easily replaced with no effect on the rest of the system. Because of the energy efficiency of the modern equipment, the cumulative running costs have also been dramatically reduced.
A novel feature has been the introduction of planting berms within the lakes. These have been designed to influence the flow patterns and reduce areas of still water. They have also been planted up with a range of aquatic plants, to act as a nutrient sink, thereby helping to reduce algal blooms, which had been a feature of the lakes since they were first constructed.
“Our client - the Corporation of London - was particularly supportive and the results,” said Chris, “have been well-received by the 2,000 residents living within the Barbican and the many other visitors to the complex. This has been largely due to the proactive steps taken by the Corporation to keep the various residents’ associations briefed on the progress of the works throughout.”
The only residents who have not been so helpful have been the wildfowl on the lakes. “As soon as the plants started going in,” said Chris ruefully, “a pair of Canada geese dropped out of the sky like Harrier jump jets and did an equal amount of damage. Of course the ducks provide plenty of enjoyment for users of the Barbican’s facilities, but they have no respect for planting programmes. We are loathe to place intrusive protective fencing around the planting berms, which would detract from the visual amenity, but the plants certainly need to be given an opportunity to get established. This is an issue we still have to resolve!”
An essential element of the water quality improvement programme was to radically alter the nature of the fish population within the lakes. The original carp served only to disturb the bed of the lakes, leaving the water coloured and unsightly. These were removed by the Kingcombe Aquacare team at the outset of the operation by electric fishing. After careful health screening and approval from the Environment Agency, they were stocked out into other waters. They have now been replaced by 1,000 golden orfe fingerlings which will grow up in the water to provide a more interesting display and, most importantly, less impact on the water environment.
Of course, the story does not end here. No water restoration project is complete without a firm sense of commitment and sufficient budget allowance for regular maintenance. The Corporation of London have taken this on board, realising that this scale of investment would be pointless without a continuing programme of maintenance to keep the waters looking at their best. This commitment has been taken on board by the Barbican staff, who take great pride in the appearance of their home patch, and wish to ensure that the water features once again reflect the impressive architecture that surrounds them.
In its simplest but most important form, this requires a constant vigil for litter, the scourge of so many urban water bodies. With a cafeteria sited on the terrace right alongside the main lake, there is ample scope for windblown debris to be carried into the water. Conscious of this challenge, Kingcombe Aquacare designed the water flows to encourage litter to collect in several easily accessed points around the lakes, allowing for ease of maintenance. However, there will always be the requirement for a man with a net to remove the accumulated rubbish from the water on a regular basis.
The array of pumps and flowmakers have been designed as stand-alone items, each group individually controlled and powered. As they reach the end of their service life so they can be easily replaced, without any impact on the continuous operation of the other equipment.
The other significant maintenance item is to continue with the protection and then the management of the planting berms. Once fully established they will provide a welcome soft element within the otherwise hard landscape, whilst providing nesting sites and sanctuary for the very ducks which currently are so keen to destroy them!
Working with Nature in such an artificial environment as the Barbican lakes has presented Kingcombe Aquacare with a host of challenges. But as Chris Keech summed it up “rising to those challenges and helping Nature to help herself is what makes our work so rewarding.”