The Santa Fe region is rapidly growing.  The Santa Fe 
Group aquifer in the Espaņola basin is the main source of 
municipal water for the region and water 
shortfalls could have serious consequences.  Future growth 
and land management in the region depends on accurate 
assessment and protection of the region's groundwater 
resources.  An important issue in understanding the ground 
water resources is a better understanding of the 
hydrogeology of the Santa Fe Group, the sedimentary 
deposits that fill the Rio Grande rift and contain the 
principal groundwater aquifers.

The U. S. Geological Survey (USGS) is conducting a 
series of studies of the Espaņola basin in northern New 
Mexico.  One objective of these studies is to understand 
the hydrogeologic framework of the Espaņola basin so as to 
help land managers plan and develop water supplies.  These 
studies involve a multi-disciplinary approach to better 
understand the critical aquifers in the intracontinental 
rift environment.  Detailed geologic mapping, high-
resolution airborne magnetic surveys, electromagnetic 
surveys, as well as hydrologic, lithologic, and 
hydrogeochemical data are being used to refine 
understanding of the aquifer systems in the Espaņola basin.  
A magnetotellluric (MT) survey was conducted as part of 
this work.  The primary purpose of the MT survey was to map 
changes in electrical resistivity with depth that are 
related to lithologic variations important to the critical 
aquifers.  The purpose of this report is to release the MT 
sounding data; no interpretation of the data is included.