A water balance model to study the hydrological response to different scenarios of deforestation in Amazonia

Abstract

Summary Amazonia encloses some of the largest watersheds in the world, experiencing substantial amounts of rainfall annually and producing more runoff to the ocean than any other region. Amazonia experiences one of the highest rates of deforestation in the world and the hydrological effects of such a disturbance have already been investigated by several studies. Contrasting results exist, especially when different scales and degrees of heterogeneity are considered. This paper assesses the dependency of the hydrological impact of deforestation on these factors through application of a gridded water balance model. The model simulates different scenarios of deforestation based on straightforward water balance calculations. In all experiments performed, the scenarios conform to observations of decreased evapotranspiration within disturbed sites. Initially, by implying an uncoupling between small deforested areas and circulation, the model suggests an increase in runoff locally. However, when the land-atmosphere coupling caused by intermediate levels of deforestation is reproduced through deviations on circulation, the model confirms that the water cycle may or may not become regionally accelerated, depending on the degree of heterogeneity associated. Finally, by simulating a scenario of complete deforestation, the model confirms expectations of a less intense water cycle in Amazonia. Due to the broad range of numerical models and observation networks currently available, the importance of the proper representation of both scale and heterogeneity of deforestation to the correct assessment of its hydrological effects is emphasized. Despite our model results, there is need for more mechanistic studies on coupled land-surface and atmosphere interactions under varying conditions.