TADEU, N. D. Assessment of water impacts of eucalyptus monoculture in the portion of the Basin of the Paraíba do Sul River in São Paulo (BRASIL). Master's Thesis. Graduate Program of Environmental Science, Universidade de São Paulo, São Paulo, 2014.Modifications in the natural land cover can change the hydrological cycle, which might have an impact on water availability. In the river basin of the Rio Paraíba do Sul (RBPS), the natural vegetation has been being replaced due to the expansion of eucalyptus monocultures. This research assessed the impacts on water availability (both qualitative and quantitative), caused by eucalyptus forestry for pulp production in the RBPS part in Sao Paulo. The water footprint (WF) method was applied to assess the water used on the cellulose production of native forest and eucalyptus, given the use of this method by the industry. Also, the Climatic Water Balance, General Water Balance methods and the Ecosystem Services approach were used in order to perform an extended and integrated analysis of the hydrological behavior of the basin. By analyzing these methods, it was found that the products WF only assesses the efficiency in water use, which can mask high water consumption with higher productivity per hectare. This because a smaller value for wood WF was observed, in m 3 per ton for eucalyptus, and higher total water use, in m 3 per hectare peryear, compared to the native forest. The results observed by the Climatic Water Balance analysis for the main vegetation cover showed that the eucalyptus presented higher evapotranspiration and smaller water surplus. The General Water Balance, analyzed on a monthly basis, showed that the vegetation has an impact on the water provision service and competes for water with other users in the basin (natural and anthropic) in periods with less precipitation. Finally, it was concluded that local measurements are required to determine the runnof volumes (superficial and subsurface), infiltration, as well as the process of leaching and soil loss in order to have a more accurate assessment of the hydrological impacts of the eucalyptus monoculture.