ILWAS model: formulation and application

The Integrated Lake-Watershed Acidification Study (ILWAS) model was developed to predict changes in surface water acidity given changes in deposition acidity (see preceding six abstracts). The model was primarily developed to predict surface water hydrogen and aluminium concentrations because of their importance to fish, but it also simulated the routing of water to streams and lakes and the major alkalinity-producing and consuming reactions occurring along the flow pathways. The model was based on an extended form of the alkalinity expression and included both equilibrium and rate process formulations. It represented a unified theory of lake acidification quantified by the equations and algorithms embedded in the model code, and could be used to test scientific hypotheses and to answer management questions.