Identifying watershed-scale barriers to groundwater flow: Lineaments in the Canadian Shield

Abstract

Lineament identifi cation is a standard but controversial hydrogeologic practice. In this study, we present a rigorous examination of the hydrology of lineaments in a crystalline bedrock setting. Lineaments are reinterpreted as watershed-scale hydraulic barriers, in contrast to previous interpretations as fractured conduits that focus recharge and fl ow. In the study area, an ~900 km 2 watershed underlain by the granitic and gneissic terrain of the Canadian Shield, bedrock lineaments are associated with linear lake shores and perennial wetland complexes. Lineaments were identifi ed using a robust multi-image method and characterized by remote sensing, fracture mapping, drilling, hydraulic characterization, and numerical simulation of a coupled groundwater-surface-water system. Results indicate that two principal lineament sets are oriented parallel to fracture and fault orientations, and thus lineaments are interpreted as structural features, either fault zones or fracture zones with limited displacement. Faulted lineaments are more effectively identifi ed by digital elevation model (DEM) topographic data rather than Landsat tonal imagery. Hydrogeological characterization and geomatic data indicate that the fractured bedrock underlying lineaments is composed of poorly connected zones of reduced permeability due to fault zone and/or fl uid fl ow processes. Field data and numerical simulations suggest that lineament areas are barriers to recharge and fl ow in this setting as a result of permeability reduction. Integrated data sets and models of lineament permeability that are geologically realistic result in a better understanding of fractured bedrock aquifers and patterns of fl uid fl ow in the brittle uppermost crust.

Discontinuous Nature of Phreatic Aquifers in Granitic Rocks at Watershed Scale: A Stratiform Model from Perennial Streams and Well Data

“…The barrier effect due to fault gouge has been reported elsewhere for such fault zones through Precambrian rocks in other geological contexts [20]; [21]. Actually, rains are abundant (between 1600 mm and 1800 mm) and reach a peak around June and July.…”

Characteristics of direct human impacts on the rivers Karun and Dez in lowland south-west Iran and their interactions with earth surface movements

“…Such a vertical displacement appears to be manifest as fairly steep valley slopes (6.121 Â 10 À4 m m À1 ) for this reach of the River Gargar, with the high channel sinuosity (3.195) developing to maintain fairly typical Gargar channel water surface slopes (5.65 Â 10 À5 m m À1 ) across the slight vertical displacement of the lineament (Woodbridge, 2013). The EeW meander orientation for this reach most probably is related to the approximate EeW orientation of the lineament and associated joints, especially since they may act as hydraulic conduits or barriers (Park, 1997;Gleeson and Novakowski, 2009;Gay, 2012). The River Karun (Shuteyt) and the River Dez flow across this extensive structural lineament with no notable geomorphological modifications (Fig.…”

Groundwater sources and geochemical processes in a crystalline fault aquifer

“…Groundwater flow at depth depends on rock porosity, fracture aperture distribution and connectivity of the fracture network. Specifically, fault zones can affect a large area of a massif and can greatly influence fluid flow at the regional scale (Bense and Person, 2006;Bense et al, 2013;Evans et al, 1997;Forster and Evans, 1991;Gleeson and Novakowski, 2009;Rojstaczer et al, 1995). Fault zones are characterized by an internal structural complexity (Bense et al, 2013;Caine et al, 1996) which control their capacity to drain or to act as barrier to groundwater flow.…”