Electrochemistry allows for rapid identification of multiple metals and other chemical complexes common in acid rock drainage (ARD) systems. Voltammetric scans using a single gold microelectrode of water samples from geochemically distinct areas of the Río Tinto (RT) in southwestern Spain were clearly recognizable in the field and in samples stored at room temperature for over 6 months. Major voltammetric peaks of iron(III) and copper(II) were identified on a single constantly renewable gold microelectrode. Confirmation of these peaks was performed by spiking with standard metal solutions in the laboratory. This voltammetric technique is a rapid, direct and inexpensive in situ method for identification of water sources and their chemical characteristics, as well as an economical way to monitor environmental changes and remediation efforts.