In a Joint Venture of German Consultants for the sustainable development of the Guarani Aquifer, funded by the Bavarian Government, part of the Guarani Aquifer has been investigated (see http://www.abg-guarani.de).
Külls, C. 2003. Groundwater Recharge of the Guarani Aquifer. Previous investigations, estimation methods and recommendations. Report to the Instituto Geologico, Sao Paulo. 19 p.
Tröger, U., Dias, C.L., Guillaumon, J.R., Iritani, M.A., Külls, C.; Schuler, G. 2004. Remarks and new data about the recharge of the Guarani Aquifer System. In: IAH, IAH Congress, 34, Proceedings, Zacatecas, México. (Keynote)