Electrical resistivity and ground-penetrating radar as tools to characterize groundwater surface water interaction at Mirror Lake, NH

The results of electrical resistivity surveys using both surface-towed and stationary (lake bottom) cables at Mirror Lake, NH suggested that resistivity surveying can be useful for characterizing geologic heterogeneities that control groundwater-surface water interaction, as well as for imaging road salt contamination. In-situ measurements of seepage coincident with resistivity surveys suggested a relationship between resistivity values and seepage rates. Specifically, we observed that seepage rates were low (averaging-20 cm/day) at Mirror Lake where resistivity values were greater than or equal 3000 O-m and where they were less than or equal to 200 Q.- m. Low (200 fl-m) resistivity values were indicative of organic matter deposits. High (3000 fi-m) resistivity values were indicative of low porosity, poorly sorted till. Intermediate (-1500 H-m) resistivity values were observed in the regions where seepage rates were highest (averaging-80 cm/day). Core, modeling, and slug test data suggest that these intermediate resistivity values reflect well-sorted, higher-porosity glacial drift. Resistivity surveys of the suspected region of salt contamination revealed a plume-shaped feature of low resistivity. Low resistivity and higher chloride content were confirmed by laboratory analysis of pore fluid. The results of ground penetrating radar (GPR) surveys suggested that this technique can also identify geologic features that relate to seepage. GPR surveys identified the bounds of a blanket of organic matter that covers the bottom of Mirror Lake; previous work suggested that this organic matter controls seepage there. Radar also confirmed the results of previous work at Mirror Lake about the distribution of cobbles and boulders there. We conclude that the rapidly acquired towed-cable resistivity survey and ground-penetrating radar surveys can guide placement of higher-resolution, more time-consuming stationary cable surveys. The use of stationary cable resistivity surveys in the very near-shore environments (< 2 m from shore), which are generally inaccessible with a towed-cable survey and yield very low resolution GPR images, can guide seepage meter placement.

Grantor dc:publisher

Temple University. Libraries

Year dc:date.issued

2008

Author dc:creator

• Mitchell, Natasha

Advisor dc:contributor.advisor

• Nyquist, Jonathan

Committee members dc:contributor.committeemember

• Toran, Laura E.
• Tumarkin-Deratzian, Allison

• Hydrology
• Geology

Statement dc:rights

• IN COPYRIGHT- This Rights Statement can be used for an Item that is in copyright. Using this statement implies that the organization making this Item available has determined that the Item is in copyright and either is the rights-holder, has obtained permission from the rights-holder(s) to make their Work(s) available, or makes the Item available under an exception or limitation to copyright (including Fair Use) that entitles it to make the Item available.

Language dc:language.iso

eng

Repository record dc:identifier.uri

https://scholarshare.temple.edu/handle/20.500.12613/12100

OAI identifier oai:identifier

oai:scholarshare.temple.edu:20.500.12613/12100