Phosphorus dynamics following restoration measures in the Loosdrecht Lakes (The Netherlands)

Water quality conditions in the Loosdrecht lakes, a system of interconnected lakes about 20 km south of Amsterdam, were studied, with particular reference to phosphorus dynamics. Between 1980 and 1986, phosphorus loads were significantly reduced by excluding wastewater discharges and removing phosphorus from the water used to control lake levels. Total phosphorus and chlorophyll-a concentrations were reduced in Breukeleveen lake, though not in Vuntus and Loosdrecht lakes. Phosphorus was still contributed to by external sources, release from sediments, and excretion by large crustacean zooplankters and by fish. Further measures to reduce phosphorus concentrations were required to accelerate recovery of the lakes.