Optimization of monitoring programmes by means of general correlations between standard water quality variables

Summary

Based on results from a long-term high-frequency lake water study in Sweden carried out in a diverse group of eutrophicated lakes and flowing waters, general seasonal and annual fluctuations are presented for common water quality variables. Strong relationships were found between maximum and average values indicating that a certain base level of a constituent is needed for high peak values to occur. A statistical evaluation of sampling frequencies revealed that a bi-monthly sampling (February, April, June, August, October and December) is necessary if a ± 10 % precision is to be achieved regarding both loading and water quality aspects. In order to run a comparatively frequent sampling programme the number of sampling localities ought to be restricted to strategically chosen study sites. A prerequisite for such a programme is the availability of reliable figures for the pollution load from diffuse and point sources. Different ways are discussed for optimization of monitoring programmes and increasing their predictive power and for planning methodology in managing lake eutrophication.