Modeling perspective of the deforestation impact in stream water quality of small preserved forested areas in the amazonian rainforest

A long-term predictive model, MAGIC, was applied to a Central Amazonian catchment area to illustrate large scale deforestation effects on ‘islands’ of preserved areas, for the situations with and without climate changes. In addition, model sensitivity in response to different organic matter levels in the soil and stream waters as well as to different Al solubility constants was evaluated. The model output was strongly dependent on the chosen values of organic matter concentration and Al solubility constant. Application of the model to a 30 yr deforestation program revealed increases in streamwater ionic concentrations with or without climate change, although streamwater ionic concentrations were predicted to be higher as a consequence of climate change. On the centennial scale, streamwater ionic concentrations reach a new equilibrium, with concentrations higher than those prior to the surrounding deforestation. With the assumed increased cation deposition to the preserved forest areas, soil exchangeable cation concentrations increase with time and aluminum is released to solution. At the end of the simulated deforestation program, SO ₄ ^2? in the preserved areas began to be released to streamwater, inducing acidification. Application of the MAGIC model makes possible to estimate, for the rainforest environment, water quality changes as a function of different climate and land use changes.