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Combining airborne electromagnetic induction and hydrochemistry to quantify salinity contributions to a large basin stream, Colorado River, Texas, USA
Author(s) -
Paine Jeffrey G.,
Collins Edward W.,
Nance H.S.,
Niemann Kerry L.
Publication year - 2009
Publication title -
near surface geophysics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.639
H-Index - 39
eISSN - 1873-0604
pISSN - 1569-4445
DOI - 10.3997/1873-0604.2009016
Subject(s) - hydrology (agriculture) , geology , salinity , streams , groundwater , environmental science , structural basin , surface water , streamflow , subsurface flow , sampling (signal processing) , drainage basin , geomorphology , oceanography , computer network , geotechnical engineering , cartography , filter (signal processing) , environmental engineering , computer science , geography , computer vision
We combined multifrequency airborne electromagnetic induction (EM) measurements of apparent ground conductivity with chemical analyses of surface water to delineate natural and oilfield salinity sources that degrade surface water quality by elevating total dissolved solids, chloride and sulphate concentrations along several hundred kilometres of the Colorado River (western Texas, USA). To reduce the cost of airborne geophysical surveying over such large areas, we used a helicopter to tow an EM instrument at low altitude along the stream‐axis and measure the apparent electrical conductivity of the ground at multiple frequencies, examined results in the field to identify salinized stream segments and optimal water sampling locations and then flew more detailed surveys over these limited areas rather than over the entire basin as is typical in salinization studies. Minimally processed stream‐axis EM data (including apparent conductivities measured at single frequencies and multifrequency ‘spectrograms’ along the stream‐axis) helped identify salinized streambed segments, discriminate between surface and subsurface sources of salinity and determine water sampling locations upstream and downstream from each segment. We integrated EM, streamflow and hydrochemical data to calculate salinity loads, identify specific natural and oilfield salinity sources and guide and implement remediation efforts. Stream‐axis flight lines offer the advantage of rapidly acquiring high‐resolution subsurface conductivity data along long stream segments where traditional gridded flight‐line surveys and waterborne measurements are impractical or prohibitively expensive. They also overcome difficulties associated with topographic effects when surveying deeply incised streams. Such surveys provide valuable information on location, extent and type of salinization and can guide water sampling and more intensive ground or airborne measurements.