HR: 1400h
AN: H53E-05    [Abstracts]
TI: Geophysical and Hydrological Characterization of Alluvial Fans in the Valle El Sauz Encinillas, Chihuahua, México.
AU: * Villalobos-Aragón, A
EM: avillalobos4@utep.edu
AF: Department of Geological Sciences, University of Texas at El Paso, 500 W. University Ave., El Paso, TX 79968, United States
AU: Chávez-Aguirre, R
EM: rchavez@uach.mx
AF: Facultad de Ingeniería, Universidad Autónoma de Chihuahua, Nuevo Campus Universitario, Chihuahua, CHI 31160, Mexico
AU: Osuna-Vizcarra, A
EM: aosuna@uach.mx
AF: Facultad de Ingeniería, Universidad Autónoma de Chihuahua, Nuevo Campus Universitario, Chihuahua, CHI 31160, Mexico
AU: Espejel-García, V V
EM: vvespejel@utep.edu
AF: Department of Geological Sciences, University of Texas at El Paso, 500 W. University Ave., El Paso, TX 79968, United States
AB: The Valle El Sauz Encinillas (VESE) is located 92 km north of Chihuahua City, México. Despite being the principal aquifer feeding Chihuahua City, and being flanked by two well studied geological features (Bloque Calera-Del Nido to the West, and the Sierra Peña Blanca to the East), a lack of available hydrogeological data prevails in the valley. The goals of this study are two: 1) geomorphometrical analysis of the sub-basins and alluvial fans, and 2) determination of the alluvial fan geoelectrical units via electrical-resistivity soundings. The Basin and Range system forms a closed sub-basin with a lacustrine basin system in extinction process. The aquifer is located in alluvial Quaternary sediments, with varying granulometry, reaching a thickness of 600 meters at the center of the valley. The biggest alluvial fan in the VESE is located at the Cañón de Santa Clara, and intersects the playa-lake deposits of the Laguna de Encinillas. This fan has a surface of 73.2 km² and an average slope of 0.437°. The geomorphometrical analysis included the sub-basins, currents, and the fans in the area. These analyses allow a comparison between alluvial fans in the VESE and those in Death Valley, California, USA. The alluvial fans in both areas show a similar behavior in all plots. Twenty electrical resistivity soundings (Schlumberger array, AB/2 distance of 400 m) were performed in the alluvial fan. The basement and four other geoelectrical units were identified in the fan. The geophysical data, granulometric determinations, plus geochemical information of twelve wells in the area were analyzed. These data show how the decrease in granulometry, both frontally and laterally in the fan, results in a rise of the hydraulic conductivity and transmisivity values (water wells in Los Sauces and El Faro). However, both the permeability and the water quality in its distal portion, are affected by the playa lake deposits, the raising ratio of clay-size sediments (and evaporites) in the center of the valley, near to Laguna de Encinillas.
DE: 1824 Geomorphology: general (1625)
DE: 1835 Hydrogeophysics
DE: 1855 Remote sensing (1640)
SC: Hydrology [H]
MN: 2007 Joint Assembly