Recent land-use change in the catchment of Llangorse Lake, Brecon Beacons National Park, Wales

1. The deterioration in biodiversity of Llangorse Lake has been attributed to eutrophication, power-boating or a combination of the two. 2. Nutrient input responsible for the eutrophication of Llangorse Lake has been attributed to sewage effluent. This study examines potential contributions from agricultural activity. 3. The current view that increased power-boating and water skiing have had an adverse impact on the flora and fauna of Llangorse Lake is examined. 4. Land-use changes in the catchment of the lake are described, analysed using a Geographical Information System (GIS), and related to change in numbers of livestock. 5. Analysis of data since the lake was first used for power-boating in the 1950s does not indicate a significant increase in activity since the 1970s. The literature on the environmental effects of power-boating indicates the complexity of the impact, but no conclusions can be drawn. 6. It is concluded that, whilst the land-use distribution has not changed significantly for many decades, there has been an increase and intensification in the use of improved pasture, resulting in a significant rise in cattle and sheep numbers. This could have increased nitrogen and phosphorus inputs to the lake. The study indicates the importance of considering land-use when assessing causes of eutrophication. Copyright (C) 1999 John Wiley & Sons, Ltd.