HESS Hydrology and Earth System Sciences HESS Hydrol. Earth Syst. Sci. 1607-7938 Copernicus Publications Göttingen, Germany 10.5194/hess-1-197-1997 Acidification in Three Lake District Tarns: Historical Iong term trends and modelled future behaviour under changing sulphate and nitrate deposition Whitchead P. G. 1 Barlow J. 2 Haworth E. Y. 3 Adamson J. K. 4 Aquatic Environments Research Centre, Dept. of Geography, University of Reading, Whiteknights, Reading, RG6 2 AB. Dept. Civil Engineering, Imperial College, University of London, Exhibition Road, London W1. Institute of Freshwater Ecology, Ferry House, Ambleside, Cumbria, LA22 OLP Institute of Terrestrial Ecology, Merlewood Research Station, Grange over Sands, Cumbria, LA11 6JU 31 03 1997 1 1 197 204 Copyright: © 1997 P. G. Whitchead et al. 1997 This work is licensed under the Creative Commons Attribution-NonCommercial-ShareAlike 2.5 Generic License. To view a copy of this licence, visit https://creativecommons.org/licenses/by-nc-sa/2.5/ This article is available from https://hess.copernicus.org/articles/1/197/1997/hess-1-197-1997.html The full text article is available as a PDF file from https://hess.copernicus.org/articles/1/197/1997/hess-1-197-1997.pdf

Three upland Lake District Tarns, Scoat, Greendale and Burnmoor, have been evaluated using MAGIC (Model of Acidification of Groundwater In Catchments) to reconstruct past, present and future chemical behaviour. The modelled historical changes in acidity are compared with palaeoecological estimation of pH to demonstrate model validity. Chemistry as simulated for all anions and cations and two of the three lakes are shown to have undergone significant acidification. The effects of changing atmospheric pollution levels on lake chemistry is evaluated and 80-90% sulphur reduction levels are required to achieve zero alkalinity. The impacts of increased nitrogen deposition are assessed and are shown to further delay reversibility.