From Bureau of Economic Geology, The
University of Texas at Austin (www.beg.utexas.edu).
Bureau Seminar, March 30, 2007
Flying the Colorado: Finding Salinity Sources
Bureau of Economic Geology, Jackson School of Geosciences, University of Texas at Austin.
Salty water in West Texas has farmers and water suppliers pointing at oil producers, oil producers pointing at Permian evaporites, and everyone pointing at salt cedar. Salinization of soil and water, from whatever source, is a growing threat to agriculture and water supplies, not only in West Texas but also in arid, coastal, and former oil producing areas worldwide. The increase in electrical conductivity that accompanies salinization makes geophysics an especially effective tool in salinization studies, but used alone can only provide circumstantial evidence of salinity sources and types. Ongoing collaborative investigations along the upper Colorado River present a rare opportunity to iteratively integrate results from an airborne geophysical survey, well drilling and water analyses, and ground- and borehole-geophysical measurements. Airborne electromagnetic induction (EM) data acquired along 437 km of river and tributary stream axes in 2005 identified discrete salinized streambed segments, including several near oil fields. A round of monitor wells in one of the oil fields verified groundwater salinization but failed to delineate salinization nor identify specific sources. Subsequent ground and borehole geophysical surveys complemented airborne EM and well data by establishing lateral and vertical salinization bounds, discovering source areas, and guiding remedial activities. A similar approach applied to other large river basins in Texas and elsewhere could rapidly identify important salinity sources and prioritize remedial actions.