Macrophytes provide habitats for fish and smaller animals, they bind sediments, protect banks and absorb nutrients. Macrophytes can indicate the impact of increased nutrients in rivers and are also influenced by other pressures such as channel engineering, water abstraction, flow impoundment or acidification. The types and amount of macrophytes present in a river can tell us how well that river is working.
This method uses the principle that different macrophytes are associated with different amounts of nutrients (especially phosphorus) and flow conditions. Different combinations, quantity and numbers of macrophytes are expected to be present depending on the river type and its fertility.