them. The infiltration rate depends on parameters that are variables in time and space. Another important factor that contributes to the aquifer's recharge is the importance of evapotranspiration. The soil, plants and atmosphere could be considered as components of a system physically related and dynamic. In some regions, the quantity of water that evaporates is larger than the runoff flow. A study by Brazilian Agricultural Research Corporation (Embrapa) in Ribeirão Preto - Brazil, from 1994 to 2001 indicates that agricultural activity using chemical products offers risk of contamination for the groundwater. Vegetal interception is another factor that directly influences the quantity of water that infiltrates into the soil, according to Soares and Almeida (2001) who realized a study in the Eucalyptus area between October 1995 and September 1996. The interception during this period was evaluated in 11% of the precipitation value. See also Aquifer Fossil water Groundwater Ogallala Aquifer References External links Official Site for the book about the Aquifer, by Nadia Rita Boscardin Borghetti, José Roberto Borghetti and Ernani Francisco da Rosa Filho (in Brazilian Portuguese) Conference «The Management of the Guarani Aquifer System: An Example of Cooperation» Aquifers of South America Geography of South America Aquifers Aquifers in Brazil Springs of Argentina Springs of Brazil Springs of Paraguay Springs of Uruguay