Bankside reservoir

A bankside reservoir is a reservoir generally sited close to a river from which water is pumped to be used for potable water supply.

The use of a reservoir in this way provides a significant degree of biological and physical treatment for the water. Bacterial levels typically fall by several orders of magnitude and the level of suspended matter also falls significantly. This is particularly advantageous in enabling the use of lowland river waters which may be carrying pathogens from upstream agricultural use or sewage disposal. A bankside reservoir also provides a substantial reserve of water in the event that the riverine source becomes unacceptably polluted. In such cases the inlet is closed until the pollutant has passed. There are disadvantages to the use of a bankside reservoir; it requires a very large area of land adjacent to the river. In summer, it can support explosive growths of blue-green algae that can reach bloom proportions, causing unacceptable levels of toxins to be present the water.