The Iberian Pyrite Belt( IPB) is rich in sulfide deposits which have been intensively exploited, generating a huge problem of contamination of the Odiel River by acid mine drainage( AMD). At its source is a clean river, but along a 7 km-long reach receives five discharges of acid mine waters: Concepcion, San Platon, Esperanza, Poderosa and the Agrio River, which drains the AMD contaminated water from the Rio Tinto mines. The flows and hydrogeochemical characteristics of these AMD sources have been studied. The Agrio River is the main contributor of acidity, sulfate and metals to the Odiel River due to its high flows and pollutant concentrations. San Platon and Poderosa mines have high sulfate and metal concentrations although both sources are characterized by low or moderate flows while Concepcion has the lowest concentrations but higher flows. The composition of AMD sources seem to be controlled by the mineralogy of the deposits and by geochemical processes. Strong seasonal variations are observed for some AMD sources while others are more constant throughout the year. (C) 2017 The Authors. Published by Elsevier B.V.