R.W. Edwards - Böcker

This book brings together research into the process of stream acidification and its impact on Welsh surface waters, carried out over the past decade or so. It is perhaps surprising that not until the 1980's was clear evidence of stream acidification assembled. In Wales, concerns over pollution had focused water quality sampling principally on the areas of traditional heavy industry and large urban popula­ tions served by inadequate sewerage systems and sewage disposal arrange­ ments. Mistakenly, it had been assumed that, with its prevailing westerly winds, Wales would receive precipitation substantially unpolluted by the industrial and urban emissions from Britain and mainland Europe. Assurance of the high quality of Welsh upland streams, the traditional nursery ground of salmonids, was eroded particularly by studies in the vicinity of Llyn Brianne reservoir in the catchment of the River Tywi of Central Wales. These demonstrated a clear correspondence between the biological quality and fisheries of streams in the catchment and aspects of stream chemistry, par­ ticularly pH, aluminium and calcium on the one hand, and catchment land­ use on the other. It is salutary to record that the first signals were of an inexplicable failure of the runs of migratory salmonids into the upper catchment, occupied by the Llyn Brianne reservoir and its influent streams, and the failure to restore the fishery by re-stocking with eggs and fry. Only then did the significance of the recent decline in some other upland lake and reservoir fisheries in Wales become apparent.

The valley of the River Wye has long been famed for its natural beauty and the salmon stocks which the river supports. As one of the largest substantially unpol­ luted rivers in Southern Britain, the Wye, which rises in Wales and flows into England, is now of considerable significance in the strategy for conservation of freshwater habitats in the United Kingdom and is designated as a Site of Special Scientific 1 nterest by the Nature Conservancy Council (N. C. C. ). However, des pi te this scientific importance, published studies of the aquatic ecology of the river during the earlier decades of this century were principally restricted to the excellent series of articles and books on the salmon written by J. A. Hutton during the period 1912-47 and scattered records of the plants of the river banks. During this period the Fishery Board and successive organisations responsible for fisheries, also published reports describing general water quality and salmon catch statistics. In 1970 a survey was undertaken by the N. C. C. which provided the basis for the decision to give it special protected status. The Wye has been exploited as a major water source for Birmingham, through the development of reservoirs in the Elan Valley, since 1904. Further development of the capacity of the Elan catchment occurred in 1952 with the completion of the Claerwen Reservoir.