Standing water – lakes and ponds
Wales has about 500 lakes and large ponds,
more than 1000 small ponds. Natural lakes and ponds were mainly
created by the action of glaciers during the Ice Age, and so are
particularly concentrated in north Wales.
Many of the upland lakes are clear and are comparatively poor in
nutrients. An increasing number of lakes and ponds are becoming
enriched by minerals like nitrogen and phosphorus, which can cause
Rich in nutrients – eutrophic lakes
Naturally occurring eutrophic lakes are the ‘richest’ lake
types. They have fairly high concentrations of nutrients like
nitrogen and phosphorus which help plantlife to grow.
Natural eutrophic lakes are rare in Wales, because the right
combination of landscape and geology doesn’t happen often. Most
examples are in Anglesey, Clwyd and Powys – the largest and best
known is probably Llangorse Lake, near Brecon.
Because of the effect of human activity we know that many of the
lakes we now consider eutrophic – the most rich in nutrients – were
once considered medium-rich.
What are eutrophic lakes?
Eutrophic lakes are usually shallow and have a high diversity of
water life. Although few and far between, these lakes are
relatively important in Wales because they support a mixture of
northern and southern wildlife that are threatened in the UK as a
whole. They often have extensive areas of swamp and fen close by
and these are threatened habitats in their own right. Many are
important wildfowl sites.
Eutrophic lakes with submerged broad-leaved pondweeds are
protected under the Habitats Directive. Submerged broad-leaved
pondweeds are tall-growing species, with beautiful flat see-through
leaves. These plants are becoming steadily rarer throughout Europe,
because they need lowland lakes with clear water.