Nuttall’s Waterweed is a submerged plant characterised by small white flowers above the water. It grows in dense clusters and as a result can block waterways and increase the likelihood of flooding. It often outcompetes native species and can cause fluctuations in oxygen levels in the water, which is detrimental to some wildlife. It is now an offence to plant it in England and Wales. It is native to North America and was imported to Britain as an ornamental plant, and is thought to have been spread from ponds by human transport. It has been recorded in the lower parts of the catchment.