Mine wastes from the La Aurora mine in the state of Guanajuato were generated by the flotation process and placed in four tailing dumps on the local stream while the plant operated. Given that these wastes contain toxic elements, it is important to establish their impact on the quality of several surrounding natural sources of water that are considered potential drinking water supplies. This study identified four water source types, in which the contents of arsenic (As), mercury (Hg), and thallium (Tl) were exceeded, according to international guideline values for drinking water quality. The first type of aqueous sample corresponded to leachates produced by rainwater infiltration in tailings and water–mineral waste interactions. The second type corresponded to surface water along the Xichú and La Laja Streams, and the third and fourth types involved two groundwater well samples and spring samples, respectively. The Chiquito Stream was used as a reference area that had not been impacted by the mine wastes. The isotopic signatures associated with δ³⁴S_sulfate and δ¹⁸O_sulfate compositions from the El Ojo de Agua spring are similar to those of the Santa María River and are different from those of the mine waste leachates. This study shows evidence of the presence of As in the El Ojo de Agua spring, which results from dissolution of secondary mineral phases that were produced by alteration of the mine wastes, which then migrated along the Xichú Stream system until reaching the spring. These As-bearing fine particles are prone to dissolution when in contact with this water source. Principal component analysis revealed that the observed As, Tl, and Hg can be attributed to weathering of the mine wastes. However, the results suggest that a natural contribution of these elements could be associated with rainwater–igneous rock interactions.

The Olivargas Reservoir is located in a remote and scarcely monitored area in the Odiel River Basin (Southwest Spain) and is used for domestic, agricultural and mining water supplies. In contrast with highly monitored reservoirs, this paper explores the application of the CE-QUAL-W2 model, that was designed by Cole and Wells in 2005, to a poorly monitored reservoir and the utility of the results obtained. The model satisfactorily reproduced the water head measured continuously over three years, temperature (T), total dissolved solids (TDS), dissolved oxygen (DO) and pH measured bimonthly in a depth profile near the dam. A significant increase in TDS and decrease in DO and pH profiles were observed for four months, especially in the hypolimnion. The model reproduced changes in the parameters by assuming the occurrence of an acid water spill into the reservoir. A comparison of calculated results and measured TDS and DO prompted the conclusion that the spill consisted of approximately 3000 t of TDS (mainly sulfates) and 26 t of Fe(II) flowing into the reservoir for approximately 15 days at rates of approximately two and 0.02 kg/s, respectively.

El objetivo de este trabajo fue realizar una estimación del volumen que potencialmente podría recargarse hacia los acuíferos del municipio de Guanajuato durante el periodo de la realización del proyecto del verano de investigación en el año 2024. Se utilizó una aproximación de un balance hídrico en la cuenca del río Guanajuato-Purísima. Se contrastaron los datos de la lluvia normal de junio y julio del periodo 1960-2000 de seis estaciones meteorológicas de la CONAGUA, con los datos de los meses de junio y julio del 2024 que arrojaronn estaciones meteorológicas en línea. Se describieron las condiciones de sitios que pueden dar información sobre la recarga, tales como pozos someros y manantiales, se analizaron los aniones en cada muestra y se aplicó el método de balance de cloruros para evaluar la recarga. La cantidad de lluvia que cayó en la cuenca el mes de junio fue de 98.72 millones de metros cúbicos (Mm3) y en julio fue de 109.62 Mm3.Estos números exceden los datos normales en 1.5 y 1.2 veces para junio y julio respectivamente. Los datos reflejan que los manantiales en medio fracturado pueden recargar del 25 al 36 % de la lluvia total y los pozos en los medios sedimentarios pueden recibir la recarga del 4 al 8 % de la lluvia total.