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2007 Ground Water Summit |
Monday, April 30, 2007
4:30 p.m. - 7:30 p.m.
Tuesday, May 1, 2007
9:30 a.m. - 1:30 p.m.
Tuesday, May 1, 2007
4:30 p.m. - 7:30 p.m.
Geophysical Investigations to Map Hydrogeologic Controls of Major Springs in Ash Meadows and Karst Features Adjacent to Devil's Hole
We conducted gravity and TEM surveys in Ash Meadows to confirm the presence of a major fault. The bedrock surface suggests a ridge related to the State Line fault system and a normal fault that trends roughly north-south, which is consistent with the USGS interpretation from regional data (Blakely, 1998). The TEM data indicates that the fault transposes the upper portion of the carbonate aquifer against low permeability valley fill sediments along the trend of the major springs.
The Devil’s Hole Pupfish population has suffered a precipitous decline to approximately 38 fish in early 2006. Understanding the geometry of the conduit system that supports the pool may help save the species. We collected 62 gravity stations along two 300 foot long profile lines immediately east of Devil’s Hole. The gravity data shows several minor gravity anomalies that can be modeled as narrow, vertical low density features that resemble voids or karst features. A three component TEM pilot study was conducted and found a vertical conductor related to a fault or fracture zone. A larger scale microgravity and three component TEM surveys are planned for early 2007 to map the karst features in greater detail.
John Jansen, RGP, Ph.D., Aquifer Science & Technology/Rue Mr. Jansen has a B.S. in Geology and a M.S. and Ph.D. in Geological Sciences with an emphasis in hydrogeology and geophysics, all from the University of Wisconsin-Milwaukee. He is the Senior Geoscientist for Aquifer Science and Technology, a division of Ruekert and Mielke, Inc., working on a wide variety of ground water resource issues around the country. John has over 25 years of practical experience in hydrogeology and geophysics and is the author of over 100 technical publications and presentations on ground water related issues. He is a Professional Geologist in six states, and a Registered Geophysicist in California. He currently sits on the Board of Directors for the Association of Groundwater Scientists and Engineers (Division of NGWA) and was on the Board of Directors for the Environmental and Engineering Geophysical Society from 1998 to 2000.