Investigating the hydraulic role of a large buried valley network on regional groundwater flow

An understanding of the three-dimensional hydrostratigraphic architecture of a buried valley network, in particular the continuity of permeable units within their fill, is needed to evaluate the resource potential and role of buried valley aquifers in regional groundwater flow. In this study, a facies modeling algorithm within the exploration and production software Petrel was used to construct a geological model of a buried valley network located in the central Peace Region in Northeast British Columbia, Canada. Facies were interpreted using resistivity inversion results from an airborne electromagnetic survey (SkyTEM) and borehole gamma-ray and lithology logs. This detailed geological model and a simplified geological model of the buried valley network were used to develop two interpretive numerical groundwater flow models in MODFLOW. Calibration was performed using baseflow estimates derived using a novel approach whereby upper and lower bounds for baseflow indices were combined with streamflow estimates from the Northeast Water Tool (NEWT), a hydrological modeling tool developed for water allocation for industrial use by the British Columbia Oil and Gas Commission. The modeling results suggest that permeable deposits exist within the buried valleys, but are not regionally connected throughout the whole network, and thus do not play a significant role in the regional groundwater flow regime. However, locally extensive permeable deposits occur within the buried valleys and may offer viable water sources for domestic use or to replace existing surface-water licenses for industrial use.