Das Projekt "Modelling freshwater spatial and temporal distribution in the Brazilian territory" wird/wurde gefördert durch: Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung. Es wird/wurde ausgeführt durch: Eawag - Das Wasserforschungsinstitut des ETH-Bereichs.The riparian vegetation in Brazil is protected by the National Forest Code, and the size of the legal reserve strip is defined by the dimensions of the river, within 5 categories. In the lowest category, rivers with a width smaller than 30 m have a legal reserve of 10 m wide at each bank; the highest category is for rivers wider than 600 m, which have a legal reserve width of 500 m at each. In 2012, the Brazilian Congress voted for changes in the Forest Code, also considering modifications in the riparian legal reserve. This discussion raised the question whether the dimensions of the riparian legal reserve are adequate to prevent erosion in river basins. Brazil has a high deforestation rate, whereby most of the deforested area is converted into agriculture or pasture. Frequently, management of rural land is performed with very little attention to environmental laws, and in many cases crop plantations or pasture occupy the legal riparian reserve. Several studies have shown elevated erosion rates in river basins and high inputs of nutrient in aquatic ecosystem due to the degradation of the riparian zone (Beskow et al. 2009, Gücker et al. 2009, da Silva et al. 2012, Rocha et al. 2012), but so far there exists no quantitative evaluation of the dimensions of the riparian zone regarding its effectiveness to preventing soil erosion. Freshwater resources have been receiving large attention since the establishment of the Intergovernmental Panel on Climate Change, whose periodic reports drawn attention to the effect of climate changes on the water cycle (e.g., increase in the precipitation amount in the Amazonian Basin and in south-eastern South America, and a decrease in rainfall in the western coastal of the subcontinental areas; IPCC 2007). Brazilian national estimates of freshwater resources are very imprecise and do not account for spatial nor seasonal variation, impeding an effective national management plan of water resources. Further, the existing static estimates of available freshwater do not permit predictions regarding the impact of climate change on the water cycle in the Brazilian territory, which would be key information to identify critical zones that deserve special attention and immediate management. The Soil and Water Assessment Tool (SWAT) is a physically-based, river basin-scale, distributed hydrologic model. The program is developed to predict the impact of land management on water, sediment, and agricultural chemical yield in large, complex watersheds. SWAT is an integrated program including components such as weather, hydrology, soil temperature, nutrients, pesticides, land management, bacteria and pathogens (Arnold et al. 1998, Neitsch et al. 2005). usw.