Ireland has more than 73,000 km of river channels. If placed end-to-end, they could encircle the Earth almost twice. Three-quarters of these channels are very small streams that typically flow into larger rivers.
The longest and largest river in Ireland is the Shannon. It runs for more than 360 km from its source to the sea and discharges on average more than 200,000 litres of water per second into the Shannon estuary at Limerick, where it enters the sea. That is the same volume as 5 Olympic-sized swimming pools every minute!
Half of all the endangered freshwater pearl mussels in Europe live in Irish rivers. Riverbanks provide wildlife corridors through the countryside and give food and shelter for a wide range of animals and plants. They also serve as an important habitat for many wildflowers that support butterflies and bees.
Biological monitoring has been carried out in Irish rivers since 1971. The current national river monitoring programme covers more than 13,000 km of river channel.
What is monitored
The biological monitoring assesses:
- invertebrates (animals without a backbone)
- aquatic plants
- diatoms (type of algae)
- fish (monitored by Inland Fisheries Ireland)
The chemical parameters measured include:
- dissolved oxygen
- nutrients like nitrogen and phosphorus
The physical parameters include:
- pH (acidity)
The biology is monitored once every three years, while the physical and chemical parameters are measured several times a year. Any changes in river flow or in the physical structure of the river channel are also recorded.
Excess nutrients, like phosphorus and nitrogen, cause most problems in Irish rivers so it is important to minimise nutrient losses to water. Irish rivers also face threats from:
- siltation (suspended particles of sediment in water that clog river beds)
- invasive alien species (plants or animals that are not native and threaten native species)
- physical changes (such as dredging)
- climate change