The hydrological implications of land use change a study in the Glaslyn catchment, North Wales

Abstract

This study undertook to investigate the feasibility of assessing the water resource impacts of afforestation proposals in upland Wales. Water resource issues of most concern were identified as the effects of forestry on catchment water balances, on the acidification of surface waters and on water quality.
Water balance data for five sub-catchments of the Glaslyn were derived from a programme of field work and secondary data. These data were used to test the Calder & Newson (1979) model in its various guises and verified its utility. Several suggestions were made to make the model easier to apply.
The Hornung et al (1990b) acid susceptibility map was tested using stream water chemistry data sampled from 20 sub-catchments of the Glaslyn. It was found that soils were the most important control on stream water chemistry. The presence of conifers was linked to high aluminium concentrations. The Hornung et al (1990b) map was able to predict stream water chemistry within the Glaslyn but requires testing against a larger data set.
Water quality was assessed using routine water sampling data provided by the Welsh Water Authority, the National Rivers Authority and Welsh Water pie. These showed that untreated potable supplies would not comply with the EC 'Drinking Water' Directive. It was discovered that annual rainfall was an important control on stream water acidity and the reporting of river water quality.
A geographical information system model was developed incorporating forest suitability (Rudeforth et al 1984), acid susceptibility and afforestation soil erosion risk (Evans 1990). Areas in close proximity to potable water supplies were excluded from consideration and water losses were estimated for areas acceptable for forestry. The model was able to identify areas suitable for forestry within the Glaslyn catchment and could be used as a water resource input into upland land use planning.

Date of Award	1992
Original language	English
Awarding Institution	University College of North Wales, Bangor
Supervisor	Donald Harding (Supervisor)