ABSTRACT Understanding how watersheds evolve and change hydrologically under decades of pumping can help inform sustainable watershed management. This study involved simulating the hydrological evolution of Bertrand Creek Watershed (BCW) in the Lower Fraser Valley in British Columbia, Canada, over nearly a century of groundwater pumping to assess the long‐term impacts of steadily increasing pumping on subsurface storage, aquifer‐river exchanges and streamflow. A non‐pumping simulation was used to isolate pumping effects from natural climate variability. The results reveal that changes in subsurface storage in BCW were driven primarily by climate (water availability), with pumping exerting a secondary but detectable influence. Droughts and high pumping rates interacted, producing storage losses up to 670% more than under normal conditions, while storage gains were rare, occurring only in very wet years and reaching up to 270% more than normal. Across the entire watershed, groundwater discharge and overland flow to the river declined by an average of 6% and 8%, respectively, under pumping conditions. These reductions caused simulated streamflow at two stream gauge locations to decrease by about 11% and 4% per year, respectively, consistent with observed streamflow depletion. River to groundwater exchange is low and remained the same in both simulations. A critical shift in the hydrological regime occurred in the 1970s, when multiple large‐capacity municipal wells became operational. In recent years, these wells diverted nearly 4700 m 3 /day of water that otherwise would have discharged to the stream and accounted for 6%–7% of the simulated streamflow depletion.
Shotayo et al. (Mon,) studied this question.