Regionalization of soil base cation weathering for evaluating stream water acidification in the Appalachian Mountains, USA

Estimation of base cation supply from mineral weathering (BCw) is useful for watershed research and management. Existing regional approaches for estimating BCw require generalized assumptions and availability of stream chemistry data. We developed an approach for estimating BCw using regionally specific empirical relationships. The dynamic model MAGIC was used to calibrate BCw in 92 watersheds distributed across three ecoregions. Empirical relationships between MAGIC-simulated BCw and watershed characteristics were developed to provide the basis for regionalization of BCw throughout the entire study region. BCw estimates extracted from MAGIC calibrations compared reasonably well with BCw estimated by regression based on landscape characteristics. Approximately one-third of the study region was predicted to exhibit BCw rates less than 100 meq/m2/yr. Estimates were especially low for some locations within national park and wilderness areas. The regional BCw results are discussed in the context of critical loads (CLs) of acidic deposition for aquatic ecosystem protection.