Effects of Lithology, Structure and Stratigraphy on Surface Water Specific Electrical Conductance; South Fork of the Flathead River, Montana

<p>In the South Fork watershed of the Flathead River the two main determinants of electrical conductivity appear to be lithology and structure (faults). Limestone and dolomite produce high electrical conductivities (150 to 300 mS•cm-1), shale medium conductivities (70-150 mS•cm-1) and quartz, siltite, argillite low conductivities (0 to 70 mS•cm-1). Conductivity measurements from tributaries of the South Fork ranged from 40 to 290 mS•cm-1. South Fork River conductivity values ranged from 132 to 198 mS•cm-1. Longitudinally, the South Fork Rivers’ electrical conductivity values exhibited diurnal fluxes, but overall decreased with distance from the headwaters. In general, electrical conductivity was greater (> 150 mS•cm-1) east of the South Fork Fault, which runs parallel with the east bank of the South Fork River. The geology that covers the greatest percentage of a watershed may determine the drainages’ conductivity, however all geologies and their percent of cover should be considered when no one geology appears to dominate. This study generally assessed surface groundwater interactions in the South Fork watershed and in doing so, demonstrated how electrical conductivity, lithology and structure can be used to simplify our understanding of complex hydrologic systems. Electrical conductance data and spatial patterns identified in this study provide resource managers clues as to where aquatic biota might and do thrive.</p>

Name thesis:degree_name

Master of Science (MS)

Grantor dc:publisher

University of Montana

Year

2012

Author dc:creator

• Brickl, Melissa A

• faults
• specific electrical conductivity
• Flathead River
• lithology

Repository record dc:identifier

https://scholarworks.umt.edu/etd/361

OAI identifier oai:identifier

oai:scholarworks.umt.edu:etd-1380