Weeds are loving it, but Environment Agency is fighting back
22 July 2010
High temperatures, clear water and lots of sunshine are giving river weeds perfect conditions for growth this summer. They're growing so fast, in places you can sit and actually see them extend before your eyes.
Although the weeds are loving it, the Environment Agency certainly isn't. The Agency is responsible for keeping navigation on certain rivers open and cutting weed if it increases flood risk. But with such rapid re-growth, the weeds can't always be kept in check.
The fight back to keep navigation open and homes protected from flooding is being led by the Agency's weed harvester, being used for the first time this year on the river Great Ouse. The harvester cuts weed more deeply than a standard weed cutting boat and needs only two men to carry out the work previously requiring five. Around 1 to 3 km of river are currently being cleared each day, depending on the channel width and weed density, which is up to 3 times more than a standard boat would achieve.
Environment Agency Area Manager Geoff Brighty said: ‘The harvester is really helping us to fight back against the weed this year and is perfect for wide rivers such as the Great Ouse. On some rivers we do still have to use smaller boats, or even cut from the bank which is much slower.
‘Due to the exceptional conditions this year we have to strictly prioritise our work. We cut weed continuously from June to October, but this summer's growth means it may take us longer to get on-top of weed everywhere, but we are doing our best to deal with the worst areas.'
Some of the fish deaths currently being seen are being blamed on the excessive weed growth, but this is unlikely to be the cause in flowing rivers. Cutting weed could potentially cause more problems for the fish in shallow, static waters, as silt would be stirred-up from the river bed and reduce the amount of dissolved oxygen available for fish. But weed does consume oxygen at night and in overcast conditions, risking fish suffocating.
Geoff continued: ‘It's very disappointing to see any fish deaths, but it is a risk at this time of year as oxygen levels reduce in the water because of the weather. We can sometimes help fish by moving them out or aerating the water using compressors or putting hydrogen peroxide into the water. If anyone spots shoals of fish in distress - gasping near the surface of the water - they should contact us on our emergency hotline: 0800 80 70 60 and we will respond.'
A balanced amount of weed is necessary in rivers, providing food, shelter and habitat for a range of aquatic and water-related wildlife. Operational programmes, including weed cutting, are published on the Environment Agency web site.
