Groundwater drought: Developing quantitative indicators and mapping drought susceptible aquifer - stream systems in British Columbia

Aquifers in mountainous regions can be susceptible to periods of drought, but the aquifer response to drought is complex due to groundwater – surface water interactions. In this study, early season and drought season core indicators of groundwater drought are derived from groundwater level, streamflow and climate data. The indicators are informed by the response mechanism of the aquifer-stream system, with two end-members: recharge-driven or streamflow-driven. Generalized additive models are used to determine which combinations of predictor variables for specific regions in British Columbia are associated with summer groundwater levels. Additionally, the Standardized Groundwater Level Index is used to identify wells that had pronounced responses to drought. Drought susceptibility mapping of aquifers in the Okanagan Basin was completed using aquifer hydraulic diffusivity and well density. The classification identified five aquifers that are highly susceptible to drought. The combination of indicators and the aquifer drought susceptibility map can be used for drought-related decision-making in British Columbia.