MAGIC library for Swedish lakes: evaluation of multiple calibrations

Sweden has an official procedure for determining whether or not a water body is acidified, and thereby qualified for remedial measures such as liming. The criterion of anthropogenic acidification is that the decrease in lake pH relative to pre-industrial status be more than 0.4 pH units (?pH). The pre-industrial pH is estimated by means of the dynamic biogeochemical model MAGIC. In cases for which data are insufficient to calibrate MAGIC, an estimation of pre-industrial pH can be obtained by use of the MAGIC library (www.ivl.se/magicbibliotek). The MAGIC library consists of calibrations for hundreds of lakes and streams in Sweden. The library has a matching procedure to select the lake in the library that most closely resembles the lake to be evaluated. The ?pH of the evaluation lake is then assumed to be that of the library lake.