Impact of land-use change on nutrient loads from diffuse sources : proceedings of an international symposium held during IUGG 99, the XXII General Assembly of the International Union of Geodesy and Geophysics, at Birmingham, UK, 18-30 July 1999 / convened jointly by - the International Commission on Water Quality - the International Commission on Continental Erosion, and - the International Committee on Atmosphere-Soil-Vegetation Relations of the International Association of Hydrological Sciences ; edited by Louise Heathwaite / Wallingford (Oxfordshire - GB) : IAHS Press , 1999