from northwest of Seville to south of Lisbon. The IPB has being exploited for over 4500 years (Leblanc et al. 2000). Tartessos, Phoenicians, Carthaginians, Romans, and others all mined it, although the greatest boom in production took place in the nineteenth and twentieth centuries, mainly due to British and French interest (Carrasco 2000; Flores Caballero 1983). As a result, there are 88 mines within the Spanish sector of the IPB (Pérez-Ostalé et al. 2013) and acid mine drainage (AMD) discharges into the watercourses. There are open pits, wells, galleries, tailing dams, mining facilities, and waste dumps, the latter being the main source of contamination, especially when they were abandoned or improperly closed (Loredo and Pendás 2005). Recently, mining has resumed in the IPB due to the demand for copper in emerging countries (Grande et al. 2014). Figure 1 shows the river network and the inventoried mines in the IPB. The affected river network includes, as major receptors, the Chanza, Odiel, Tinto, and Guadiamar Rivers. Most of the mines are abandoned; only the Cobre las Cruces and Aguas Teñidas mines are operating, though others may reopen. The IPB is a unique AMD-generating source due to the magnitude and ubiquity of the AMD discharges in this metallogenic province. The Water Framework Directive of the European Union and the hydrological plans of the Tinto, Odiel and Piedras rivers basins require that some of the rivers in the area have "a good ecological status" and a water quality that will support fish (salmonids and cyprinids) by 2027. Thus, an accurate inventory of the pollution and an evaluation of the impacts of each mining site in the river network were necessary and a hydrochemical characterization of the mining leachates and receiving streams was performed for the entire province. The cause-effect relationships between processes (namely the significance of the waste dumps as AMD-generating sources) and consequences