Fig. 4. (a) Geological cross-section of the area over which the GPR (ground-penetrating radar) survey was completed. The three major stratigraphic units shown are gravel and sand, sand, and till. The vertical lines are the locations of the boreholes where core samples were collected during drilling and where the crosshole GPR survey was conducted. The unsaturated zone is 1.5 m thick. (b) Envelope of the annual temperature variation (minimum observed temperature on the left and maximum on the right) and the temperature profile on 1 July for this section of the aquifer.