Freshwater and Wetlands

Northern Ireland is particularly rich in freshwater habitats which include standing waters, running waters or rivers and wetlands.

Standing open waters are one of Northern Ireland’s most extensive natural habitats and they include both lakes and ponds. There are more than 1,600 lakes, ranging in size from little more than small ponds to Lough Neagh, the largest freshwater lake in the British Isles. Water is clearly the essential element for all of these sites, and it can vary considerably in its chemical make-up. The nutrients that plants need to grow are particularly important, and it is possible to ‘type’ lakes on the amount of nutrients that they contain.

A commonly used, basic classification of lakes is into oligotrophic lakes, with low levels of nutrients, mesotrophic, with moderate levels, and eutrophic, with high levels.
Other types are also present – for example, marl lakes represent an unusual type characterised by clear waters that are particularly rich in calcium. It is this variety, in addition to the overall extent of the habitat, which makes Northern Ireland of such importance for lakes.

Rivers and streams are numerous in Northern Ireland. They are variable in their size, form and associated wildlife, with several distinctive types present. As with lakes, water chemistry is a very important factor in influencing river types – upland rivers tend to be fast flowing, with nutrient-poor oligotrophic waters. In contrast, lowland rivers tend to be slower flowing, with waters that are rich in nutrients. A vast array of wildlife exists within them and around their surrounding banks.

Freshwater wetlands are areas of land, usually fringing standing open water, that are inundated by surface or groundwater and support vegetation typically adapted for life in saturated soils. Most of Northern Ireland’s lakes are fringed by fen, marsh and swamp. However, wetlands can occur by themselves in low-lying wet ground or poorly drained marginal grassland. Wetlands benefit us in countless ways. For instance they help prevent flooding by slowing down and absorbing water, they gradually release stored water to rivers and streams to maintain the flow throughout the summer, and recharge groundwater aquifers so our wells do not go dry.