The June 2011 eruption of Cordón Caulle volcano, Chile, deposited approximately 150-200 mm ashfall on the town of Villa la Angostura in Argentina, located approximately 50 km ESE of the vent. Due to high levels of public concern about ashfall contaminating water sources, authorities initiated an extensive program of surface water sampling. The only discernible changes caused by the ashfall were a lowering of pH to 6.1, and minor increases in dissolved calcium, potassium, magnesium and silica.