Land use change is a major factor in alterations in natural processes and cycles. Remote sensing has become an excellent tool to evaluate technological changes in land cover and land use changes over large areas, such as those occurring in the Valley of San Luis Potosi (VSLP). Here, such changes have impacted a system which is 95% dependent on the aquifer. The methodology for the present study is based on the use of satellite images for the years 1976, 1986, 1995 and 2000. To asses land use change, a supervised classification process was used with a decision tree technique and ENVI 4.3 software. The evolution of groundwater levels for the years 1977, 1986, 1995, 1998 and 2007 was also analyzed, as well as problems of subsidence and fissuring in the urban area of the valley in 2006. With the support of remote sensing, it was possible to analyze the dynamic changes in land use over large areas and highlight their impact on the environment.

Los procesos de caracterización hidrogeoquímica e interacción agua-roca en las subcuencas de Santa Catarina y Ocampo-Paraíso en la Zona Media de San Luis Potosí han permitido identificar los tipos de aguas subterráneas. Los resultados del análisis químico y el estudio geológico regional han permitido documentar los posibles mecanismos de interacción del agua con la roca. Los resultados indican que la composición del agua subterránea en cada una de estas cuencas refleja la disolución por el agua de lluvia de los minerales de carbonato y magnesio de las rocas carbonatadas de la formación del Cretácico (Formación El Abra del Cretácico) y del flujo subterráneo a través de un medio granular con fuerte influencia del material de origen volcánico. Las aguas del tipo Ca-HCO?, Ca-Mg-HCO? se modifican durante el flujo subterráneo mediante la incorporación de iones Na+ y SO?²?. En el caso de la subcuenca III de San Nicolás, se ha documentado que su relleno incluye depósitos fluviales que pueden depositarse en condiciones climáticas de regiones semiáridas. El análisis hidrogeoquímico de las concentraciones de iones mayores, litio y bromo, permitieron identificar que el agua que se extrae de la región es producto de un proceso de mezcla en la que intervienen tres miembros extremos (mezcla ternaria): El primero, Santa Catarina (C?), tiene las concentraciones más bajas de bromo y litio en la recarga ocurre en las partes de mayor altitud en la región, hacia la Sierra de Álvarez. El segundo miembro (C?), tiene valores altos del bromo, bajo en litio y se origina hacia el valle de Ocampo Paraíso. El tercer miembro (C?), tiene bajas concentraciones de bromo, alto en litio y proviene de área de San Nicolás Tolentino. Los porcentajes de mezcla indican que C?, aporta el 50%, C? contribuye con el 31% y C? aporta 19 %, del agua al sistema.

The San Luis Potosí valley is an endorheic basin that contains three aquifers: a shallow unconfined aquifer of alluvial material and two deep aquifers, free and confined. The groundwater contamination documented for the shallow aquifer generates contamination of the deep unconfined type aquifer, from which part of the population’s drinking water needs are met. This study records incipient anthropogenic contamination of two types: biogenic and potentially toxic trace elements. The studied contaminants include fecal coliform bacteria, total coliform, nitrate, and potentially toxic elements such as: manganese (Mn), mercury (Hg), arsenic (As), and cadmium (Cd). This contamination in some locations exceeds the permissible limit for human consumption. Some major consequences to health, including severe illness, may be caused by the trace elements. The present results give a first signal about the contamination of the deep unconfined type aquifer due to anthropogenic activity in the valley. This is a priority issue because this aquifer supplies drinking water, and in the short or medium term it will have an effect on public health.

This paper shows the effects caused by the combination of two factors: an anthropic factor and one natural. The leading causes of imbalance in the subsoil due to drawdown of the aquifer is reflected on the surface with the appearance of cracks on ground, then came the lateral and vertical movements called faulting. This geological phenomenon is due to a pattern of orientation is associated with a regional fault system, lateral movement is almost imperceptible but the vertical displacement becomes important because it is the most conspicuous and be responsible for the damage caused to the urban infrastructure, vertical faulting is related to the drawdown generated by intense extraction of groundwater. The demand for groundwater, increasing year by year in the past four decades because of the change in land use, the most significant change was the shift from rain feed crop to irrigated crop agriculture, this change in land use occurred on Celaya’s Valley between year period 1976-2009 was quantified by use of remote sensing and geographic information systems (GIS).