The effect of catchment afforestation on public water supplies in Strathclyde Region, Scotland

Abstract

ABSTRACTIntensive coniferous afforestation of many water supply catchments is taking place in Strathclyde Region. The current concern over the impact of this significant change in land use on the quantity and quality of water supplies is discussed. Some effects, such as high sediment run-off associated with ploughing and road development, may be of dramatic short-term effect, while others, such as reduction in quantitative yield, the development of eutrophication or acidification with aluminium leaching from soils, may take longer to materialise. Selective routine water quality monitoring work commenced in 1984 in a number of water supply catchments aimed at identifying forestry-related water quality trends. The initial results of this work are presented. Against the background of catchment land use changes, new European Community water supply standards were imposed in 1985 committing the Region to a substantial capital expenditure programme over a ten-year period in order to upgrade water treatment works. Any significant long-term changes in water quality associated with forestry activity will make this programme more costly to achieve. It is considered that the water supplies most susceptible to forestry related quantity or quality problems are the small supplies in areas of Argyll, Ayrshire and the Islands. It is suggested that the way forward is for improved advance consultation and planning on a site specific basis to protect public water supply interests.