View of the Zuidplas

The water quality in the relatively shallow pools (average depth 190 cm) is downright poor due to an excessive concentration of nutrients (phosphorus and nitrogen) caused by the droppings of a large colony of cormorants, by the intake of calcareous, alkaline basin water that reacted with the acidic peat and by dredging that actually loosened nutrients from the peat. At present, the ponds are completely separated from the outside water (so that, although the lakes can be used for navigation, there is no connection with the other lakes in the area) and attempts are being made to improve the water quality. After initial success, however, they are pretty much back to square one.
The high concentration of nutrients causes blue-green algae to grow too abundantly and swimming should be discouraged.

See: http://www.rondomdeplassen.nl/node/48

JanCK_Fietser