A geophysical, geochemical and remote sensing investigation of the water resources at the city of Chihuahua, Mexico

This doctoral dissertation is an investigation of the underground water resources of a typical urban center in and northern Mexico, the City of Chihuahua. In the first part of the investigation I analyzed by remote sensing the urban growth and the consequent water demand and supply of the city of Chihuahua over a period of 22 years (1975–1997). A linear and a regression model was successfully fit to the data and can be used to forecast future water needs based on urban growth. The second study was a gravity survey of about 200 stations and a reprocessing of about 800 earlier gravity readings in the City of Chihuahua area to define the local geologic structures. The findings were used as a first exploration step to assess groundwater resources in the area. Landsat TM imagery, 30-m resolution, was applied in conjunction with Bouguer gravity anomalies to understand and define the lateral extension of the Chihuahua, Tabalaopa Basins, and the western side of the Aldama Basin. Depth and strata thickness of these three alluvial basins were defined by gravity modeling and constrained by exploration oil well data and published stratigraphic columns. The gravity results showed that the western side of the Chihuahua Basin could be the site of potential aquifers. Also, the gravity results suggested an structural gap between the southern side of the Tabalaopa Basin and the Horcasitas Basin, likely a former course of the Chuviscar River. This gap exposes the Horcasitas Basin as another basin with promise as future groundwater source. The last part of this research focused on the groundwater pollution generated by the discharge of sewage into the Rio Chuviscar and Sacramento for decades by the City of Chihuahua. Based on a groundwater and during three consecutive years (from 1993 to 1995) the elements derived mainly from the urban sewage were identified in the Tabalaopa Aquifer. A multivariable statistical evaluation supported by a surface water sampling and analysis, and of a geologic and geochemical analysis helped to discriminate natural from urban sources. Most elements considered of primary health concern were found to be of urban origin. However, natural pollution by arsenic was perceived in the Tabalaopa aquifer, potentially threatening the municipal water wells located in the area