Long-term behaviour and cross-correlation water quality analysis of the river Elbe, Germany

This study analyses weekly data samples from the river Elbe at Magdeburg be tween 1984 and 1996 to investigate the changes in metabolism and water qual ity in the river Elbe since the German reunification in 1990. Modelling wat er quality variables by autoregressive component models and ARIMA models re veals the improvement of water quality due to the reduction of waste water emissions since 1990. The models are used to determine the long-term and se asonal behaviour of important water quality variables. Organic and heavy me tal pollution parameters showed a significant decrease since 1990, however, no significant change of chlorophyll-aw as a measure for primary productio n could be found. A new procedure for testing the significance of a sample correlation coefficient is discussed, which is able to detect spurious samp le correlation coefficients without making use of time-consuming prewhiteni ng. The cross-correlation analysis is applied to hydrophysical, biological, and chemical water quality variables of the river Elbe since 1984. Special emphasis is laid on the detection of spurious sample correlation coefficie nts. (C) 2001 Elsevier Science Ltd. All rights reserved.