Das Projekt "Bewirtschaftung des arsenhaltigen Grundwassers in der Region Lagunera, Mexiko" wird vom Umweltbundesamt gefördert und von Leibniz Universität Hannover, Institut für Wasserwirtschaft, Hydrologie und landwirtschaftlichen Wasserbau (IWW) durchgeführt. Arsenic in drinking water is considered as one of the most important environmental causes of cancer mortality in the world. The groundwater resources of the region of Lagunera/North Mexico, which represents the main source of drinking water for more than 2 million people in the area, show arsenic concentrations ranging from 3 to 443 myg/l (IMTA, 1990). Large areas of the alluvial aquifer have arsenic concentrations, which are far above the Mexican and the USEPA maximum contaminant level for drinking water of 10 myg/l (US Environmental Protection Agency, 2002). Arsenic in the region of Lagunera is mainly of natural (geological) origin and the presence within the groundwater results from to extinct, intrusive hydrothermal activities combined with sedimentary processes. Other sources are mining activities and the use of arsenical pesticides. The problem of the water supply of the region has become more acute in the recent years due to the aquifer over pumping and the regulation of the Rio Nazas and Rio Aguavanal. Within less than 50 years a draw down of the groundwater levels of more than 100 m is observed and the Mayran and the Viesa Lagoons dries out. Also the quality of the groundwater gets more worse. The proposed alliance between the IMTA, Mexico and the IWH, Germany is to develop a water management system with special considerations to the arsenic problem of the region Lagunera and to test different solution scenarios, which can help solving this and similar problems.