The Environmental Risk Assessment (ARA) of pesticides, under the responsibility of Ibama, is part of the procedure for registering a pesticide in Brazil. The main objective of this project was to compare the worst-case scenario adopted by Ibama for the ARA of pesticides in water bodies, with the most representative scenarios of soybean cultivation prevalent in Brazil. A methodology was developed to map water basins with potential for contamination by pesticides used in agriculture. Through it, municipalities in the Cerrado biome with large soybean production, in several States and different geomorphologies were selected. In the selected municipalities, the presence of lakes or artificial reservoirs was identified in approximately 3% of the mapped basins. In addition, in more than 95% of the mapped lakes, the values of the ratio of basin area and lake area were higher than in the scenario adopted in Brazil. Thus, the results obtained allowed the identification of hydrographic basins with soybean cultivation, in the Cerrado biome, in different classes of potential for contamination of water basins by pesticides. The results indicate that there is a difference between the prevailing and worst-case realistic existing scenarios and the first-level scenario currently adopted by Ibama.