The Balquhidder catchments, Scotland: the first four years

Abstract

Results emerging from the long-term forestry versus upland grassland paired catchment study conducted by the Institute of Hydrology at Plynlimon, mid-Wales, and from studies of the processes controlling the hydrological responses of areas under forest and grassland, have been accepted by the water and forestry industries as a means of determining the probable effects of afforestation in other areas of Britain. When considering proposals in the late 1970s for a further major expansion of forestry, mainly in Highland Scotland, it became apparent that insufficient information was available to predict with confidence the effects in areas where forestry would replace medium height vegetation (heather sp., bracken) or in areas where a significant proportion of the precipitation falls as snow. Against this background a consortium of interested parties (see Hall 1987), agreed in 1981 to fund parallel systems and process studies of the effects in appropriate areas of Scotland. In this paper the initial stages of the systems study, on two catchments in the Balquhidder area of Central Region, are described. Some preliminary results from phase I, in which the catchment water balances under a mature forest and a mixed heather, bracken, grass cover were obtained, are presented. These water balances suggest that water use by the partly forested catchment is lower than that by the control and also lower than Penman ET. These findings are discussed in relation to the Plynlimon results and to information gained in the current process studies. Plans for phase II of the study, in which the mature forest will be clear-felled and part of the heather, bracken, grass control will be planted, are outlined.