Vegetation (Floating River Vegetation) - Office of Public Works

watercourses will require maintenance just to control this weed. A single incidence in the River
Bandon square proved that hedge clippings of Japanese knotweed can result in the propagation of
the plant in rivers at low water levels, typically rivers most suited to floating river vegetation.
Parrot’s feather was a feature of watercourses in the Galway squares. The presence of the
plant in drainage ditches along bogs illustrates the ease with which it can spread. Methods to control
and isolate the species need to be investigated.
Another nuisance species observed in watercourses during the survey was algal growth.
Varying from emerald green to a brown colour the algae was often observed wrapped around
floating river vegetation. The algae that were wrapped around floating river vegetation appeared to
reduce the capacity of floating river vegetation to photosynthesise, therefore reducing the ability of
the plant to grow and regenerate. Eliminating the nutrient overloading of watercourses at source
should bring about a reduction in algal growth.
For most watercourses surveyed cattle had unhindered access to the water. In one case cattle
were seen paddling in shallow water. The channel in question was not a maintainable channel nor
was it directly within a Special Area of Conservation (SAC) but the water level was low and four
head of cattle were present in the water at the same time. It does illustrate the level of nutrient
loading of some watercourse, which in turn can lead to excessive plant growth within aquatic
environments (Fig. 2).
Fig. 2 Cattle accessing a recently maintained watercourse (NOT Office of Public Works channel).
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