Control of phosphorus loading and flushing as restoration methods for Lake Veluwe, The Netherlands
As a result of high nutrient loading Lake Veluwe suffered from an almost permanent bloom of the blue-green algaOscillatoria agardhii Gomont. In 1979, the phosphorus loading of the lake was reduced from approx. 3 to 1 g P.m−2.a−1. Moreover, since then the lake has been flushed during winter periods with water low in phosphorus. This measure aimed primarily at interrupting the continuous algal bloom. The results of these measures show a sharp decline of total-phosphorus values from 0.40–0.60 mg P.l−1 (before 1980) to 0.10–0.20 mg P.l−1 (after 1980). Summer values for chlorophylla dropped from 200–400 mg.m−3 to 50–150 mg.m−3.
The increase in transparency of the lake water was relatively small, from summer values of 15–25 cm before the implementation of the measures to 25–45 cm afterwards. The disappointing transparency values may be explained by the decreasing chlorophylla and phosphorus content of the algae per unit biovolume. Blue-green algae are gradually loosing ground. In the summer of 1985 green algae and diatoms dominated the phytoplankton for the first time since almost 20 years. To achieve the ultimate water quality objectives (transparency values of more than 100 cm in summer), the phosphorus loading has to be reduced further.
KeywordsOscillatoria agardhii eutrophication phosphorus laoding lake restoration lake flushing
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- HOSPER, S.H., 1980. Development of limiting values for transparency, chlorophyll, phosphate and nitrogen. Results of the eutrophication survey in The Netherlands (in Dutch). CUWVO-Riza, Lelystad.Google Scholar
- HOSPER, S.H., 1984. Restoration of Lake Veluwe, The Netherlands, by reduction of phosphorus loading and flushing. Wat. Sci. Tech., 17:757–768.Google Scholar
- VAN STRATEN, G., 1985. The process of eutrophication model development with comparative examples from Lake Balaton and Lake Veluwe. Hungarian-Dutch Seminar on Water Management Problems of Shallow Eutrophic Freshwater Lakes. April 22–26, 1985, Siofok, Hungary. Hungarian National Water Authority and the Ministry of Transport and Public Works of the Netherlands.Google Scholar