USE OF AQUEOUS CHEMISTRY OF SPRINGS TO DELINEATE AQUIFERS IN THE SIERRA TARAHUMARA, CHIHUAHUA, MEXICO

This research is part of an ongoing hydrologic survey of the Sierra Tarahumara volcanic tuff region near the village of Creel, Chihuahua, Mexico, which is being carried out in cooperation with the Tarahumara Children’s Hospital. The hospital drills water wells for the Tarahumara Indians at a cost of approximately $5000 per well, all of which must be raised through charity. However, many wells have yielded water for less than a week. The objective of this study is to provide guidelines for predicting the sustainability of a well through the use of aqueous chemistry to delineate the extent of the aquifers, and stream hydrographs to determine the recharge rate of aquifers. In October 2009, Utah Valley University students and faculty collected 75 water samples from 24 developed springs, 33 undeveloped springs, 11 streams, 2 producing wells, and 5 cisterns. This greatly expanded the data set of 26 samples collected from six developed springs, eight streams, 11 wells and one cistern by UVU in October 2008. The 75 additional water samples were tested for temperature, electrical conductivity and pH on site. Concentrations of As, the transition elements normally associated with As (Fe, Cu, Ni, Co, Mn, Zn, Cr) and F were measured with a Hach DR-2700 Spectrophotometer. Near the “Educación y Patria” school in Creel, stream discharge and stage were measured and a stream rating curve was created. Students and teachers were taught to measure stream stage, and are taking measurements at the stream on a daily basis. Groundwater recharge will be calculated using the seasonal recession method. Cluster analysis is being used to group springs and wells with similar chemical characteristics. Spatial autocorrelation methods will then be used to determine the spatial extent of clusters of springs and wells with similar chemistry. Results will be reported at the meeting.