Spatial variation in water table responses across a hillslope

British Columbia’s coastal mountains consist of catchments with steep short hillslopes and shallow soils. The hydrology is driven by the humid coastal climate, with high annual precipitation. Subsurface stormflow is generally the primary runoff generation mechanism. We examined the spatial and temporal relationships between discharge and piezometric response across a hillslope in one of these watersheds. Streamflow and piezometric data were collected for one year to determine the spatial and temporal relationships between storage and runoff. Correlations between piezometer responses, storage-discharge relationships, along with connectivity and lag-time analysis were used to identify and better understand runoff generation mechanisms. Results indicated that two distinct zones existed; a riparian zone and a hillslope zone. Each zone had very different water table responses. The hillslope was found to be disconnected from the stream for the majority of time, suggesting that streamflow predominantly comes from the riparian zone. Piezometers in the riparian zone, showed hydrologically limited responses, suggesting rapid subsurface flow, likely through the many soil pipes. The results also showed that a steady state single-valued storage-runoff model is inappropriate for this steep watershed and indicates that at least a two compartment model would be more suitable. This research illustrates the large spatial and temporal variation in water table dynamics across a hillslope. This variation can have significant implications for model design, and especially understanding solute transport in these steep forested watersheds.