An application of the MAGIC model to four high altitude lakes in Ticino, Switzerland communities

This report presents the results of a modelling exercise applied to four high altitude lakes in the Ticino region, Switzerland. In this area, acidification of high-altitude lakes situated in granitic areas was first reported in the early 1980s, as an effect of acid deposition (Mosello et al., 1992). Successively, as an effect of decreasing emission and deposition of acidifying compounds, several lakes showed signs of acidification recovery (Steingruber & Colombo, 2010a). The aim of the modelling was to reconstruct and predict lake chemistry in response to atmospheric deposition change. The applied model is MAGIC, which was specifically developed for the long term reconstruction and future prediction of soil and surface water acidification at the catchment scale (Cosby et al., 2001). The study lakes were selected on the basis of available data for the model application, and in order to be representative of the high altitude lake population in the Ticino region. They span a wide range of chemical characteristics and cover varying level of sensitivity to acidification, from highly (Starlaresc, Tomè) to moderately sensitive (Laghetto Inferiore, Laghetto Superiore) lakes. This study represents the first attempt to model long term changes in lake water chemistry, trying to evaluate the effective level of recovery (in terms of pH, ANC or other key variables) with respect to pre-acidification conditions. The model allowed a reconstruction (hindcast) of lake chemistry since 1960, and a prediction (forecast) for the period 2010-2050. The projections of future lake chemistry were obtained by applying different scenarios of atmospheric deposition reduction.