What condition is the lake in?
A simple question, but one which needs clarifying in order to give a clear answer.What is the overall state of health of the lake? Is it safe to swim in? And can we drink the water?
Overall state of health
This refers to the whole body of water and summarises various aspects:
- The “primary productivity” of the water in terms of production of phytoplankton, which depends on the presence of nutrients.
- The nature of its flora and fauna.
- The presence of polluting chemicals.
All the benefits and services which the lake offer us depend upon its overall health. Unfortunately, for around 10 years the state of the lake has been in continuous decline. This is because the bringing of nutrients into the basin, in particular phosphorus, is continually increasing. While until a few years ago the state of the lake was ‘good’, now it is only ‘sufficient’, and this trend continues to be negative. So the process of eutrophication begins.
Can we swim in the lake?
In this case we are talking of a very specific service the lake gives us, that of the pleasure of being able to swim. The suitability of the lake for bathing refers to the waters close to the shore, which are much frequented by bathers, and is measured according to the amount of dangerous pollution present, e.g.:
- faecal bacteria,
- dangerous chemicals,
- toxic algae or toxic bacteria.
This pollution, concentrated along the shores, has little effect on the overall health of the lake; one could compare it to a skin irritation in a human body which, while annoying, doesn’t constitute a menace to the overall health of that human.
While we have little information on chemical pollutants (e.g. pesticides) and polluting algae in the waters near the shore, we know with certainty that damage to the drainage system affects the lake’s suitability for bathing, with frequent faecal pollution at the mouth of the drains (especially after rain) and in the vicinity of the sewage pumping stations.
Can we drink the lake water?
Far from the sources of pollution, the lake water is good, with a low level of arsenic, and it is also “seasoned” with some phytoplankton and zoo-plankton.
