Physical and chemical aspects of Chew Valley and Blagdon Lakes, two eutrophic reservoirs in North Somerset, England


Dr R. S. Wilson, Department of Zoology, University of Bristol, Bristol BS8 1UG, England.


Chew Valley and Blagdon Lakes are two shallow, hard-water, lowland eutrophic reservoirs, situated near Bristol in the south-west of England.

Chew Lake is more turbid and richer in plankton but poorer in macrophytes than Blagdon, and is more exposed to wind action. Both lakes show evidence of transient stratification in the summer coupled to deoxygenation of the bottom water, which has led to release of nutrients from the sediments.

Severe algal blooms in Chew Lake in 1968 and the consequent filtration difficulties led to the establishment of a collaborative research programme between the University of Bristol and the Bristol Waterworks Company, to define the present biological status of the lakes, and to predict their possible future development. The work covers a wide range of measurements and observations on the limnological conditions of the lakes, which form an elegantly contrasted pair, and this paper describes their general physical and chemical features.