Groundwater–surface water interaction under scenarios of climate change using a high-resolution transient groundwater model

SummaryA three-dimensional transient groundwater flow model is used to simulate three climate time periods (1960–1999, 2010–2039, 2040–2069) for estimating future impacts of climate change on groundwater–surface water interactions and groundwater levels within the unconfined Grand Forks aquifer in south-central British Columbia, Canada. One-year long climate scenarios were run, each representing a typical year in the present and future (2020 s and 2050 s), by perturbing the historical weather according to the downscaled Canadian Coupled Global Model 1 (CGCM1) general circulation model results. CGCM1 downscaling was used to predict basin-scale runoff for the Kettle River upstream of Grand Forks. These results were converted to river discharge along the Kettle and Granby River reaches. Future climate scenarios indicate a shift in river peak flow to an earlier date in a year; the shift for the 2040–2069 climate is larger than for the 2010–2039, although the overall hydrograph shape remains the same. Aquifer water levels shift by the same interval, when compared on the same day of the year. Distal from the river, modeled water level differences are less than 0.5 m, but were found to be greater than 0.5 m near the river. The maximum groundwater levels associated with the peak hydrograph are very similar to present climate because the peak discharge is not predicted to change, only the timing of the peak.