Geostatistical Evaluation of a Monitoring Strategy for Water Quality Assessment

Abstract

Water quality samples are taken since 1993 several times per year along the river Elbe, moving upstream by helicopter from the estuary in the North Sea to the source in the Czech Republic within only three days. The river was subdivided into several environmentally distinct sections and the monitoring strategy was reconsidered in the light of a sampling optimisation technique presented by Lajaunie et al. (geoENV98 proceedings). The criterion to be optimised is the estimation variance of the composite mean of the river Elbe for a given heavy metal concentration. As there is significant autocorrelation between the samples it turns out that in some cases the sampling density could be reduced by one third altering thereby by less than 10% the quality of the estimation of the mean. Several ways of approaching the sampling optimisation problem are discussed and a case study with Zinc data is provided.