Résumé
The Potosi (San Ildefonso) dam collapse on March 15, 1626 was one of the major hydraulic disasters in the world with 4.000 human lives lost, following Jansen (1980) and Schnitter (1994). However, these Authors only consulted a paper by Rudolph, an engineer who in the 1930s rebuilt and restored the Spanish dams (1573-1621) in Potosi. Rudolph's paper (1936) had been written just using the Arzáns's draft (1711) about the silver mining capital of the XVIth-XVIIth centuries (the Central Andes, Bolivia previously Peru). With more archival and bibliographic references, we propose a new estimation of the dam disaster with 2,000 lives lost or a little bit more. A catastrophic pollution by mercury (Hg) happened immediately after the dam burst because tons of the toxic chemical element (which was indispensable to silver amalgamation) are flooded into the Potosi canal. Following our estimation. 19 t of mercury were likely swept into Pilcomayo tributaries (Rio de la Plata basin). The mercury contamination was very high (48 mg/l Hg) knowing the dam storage capacity (400,000 m3) and that all the water was spilled in about 2 hours.