Impacts of the land use and land-cover changes on local hydroclimate in southwestern Amazon

This paper investigates the effects of advancing deforestation in the southwestern Amazon on local hydroclimate. For this purpose, a high-resolution mesoscale model, coupled with a land surface model and a hydrologic routing model, is integrated for five years in two experiments, one control without changes in land use and another changing land use annually. During the rainy season, simulated higher precipitation volumes are reduced with the expansion of pasture lands. In the dry periods, mainly in August, there is an increase in precipitation over some deforested areas, which can be associated with mesoscale circulations induced by the heterogeneous surface. In general, land-use changes reduce evapotranspiration and the net radiation at the surface and increase the sensible heat flux during the dry season. In the rainy period, there is an increase in evapotranspiration with the intensification of deforestation, which modifies the other components of energy balance. Results suggest that the impact of LUCC on the local climate is more affected by conditions that generate precipitation extremes (El Nino/La Nina events) than by the abrupt increase in the annual deforestation rate. Land-use changes reduce the streamflow in all sub-basins of Ji-Parana during the dry season. In the rainy season, LUCC increases the streamflow during periods with normal precipitation conditions and La Nina in almost all sub-basins, except in the sub-basin with more than 20% deforestation.