The recovery of the polluted Clyde Estuary

Abstract

SynopsisThe Clyde Estuary is recovering from gross pollution inherited from the age of the Industrial Revolution.It is necessary now to establish the degree of recovery and determine any subsequent effects of future planning consents. Documentation on water quality was subjective until the 1960's when quantitative studies on pollution levels commenced.Much attention has been paid to dissolved oxygen (DO) levels in the estuary. The changes in the DO regime over the last ten years have been quantified with the help of multiple regression techniques. The use of these techniques in establishing the changes resulting from improvements to Dalmarnock and Paisley sewage treatment works is described. Deterministic models, based on the diffusion-convection equation, have been used to predict future DO conditions. The theoretical base of these models is outlined and examples are given of the use of the models in predicting the effects of possible developments on the estuary.Biological monitoring has also been utilised to assess estuarine recovery. Benthic data has been accumulated since 1967. Regular surveys highlight improvements in species richness, diversity and stability. Spatial and temporal population variation was investigated and the salinity tolerances of the species considered. Fish life is increasing and is now present for much of the year, although salmon are still excluded from the upper Clyde system. The lower estuary remains an important overwintering feeding ground for wader populations.