Spatial controls on groundwater response dynamics in a snowmelt-dominated montane catchment

Abstract. The role of spatial variability in water inputs on runoff dynamics has generally not received as much research attention as topography and soils; however, the influence of topography and forest cover on snow surface energy exchanges can result in asynchronous snowmelt throughout a catchment, complicating the space–time patterns of runoff generation. This study investigates temporal variation in the relative importance of spatial controls on the occurrence, duration, and timing of shallow groundwater response, utilizing a highly distributed monitoring network in a snowmelt-dominated montane catchment in western Canada. The study findings indicate that deep-soil hydraulic conductivity is a first-order control on the spatial distribution of sites that generate shallow groundwater response versus sites that experience only deep percolation. Upslope contributing area and slope gradient are first-order controls on the duration of groundwater response during peak-flow, recession-flow, and low-flow periods. Shallow runoff response areas expand and contract throughout these periods and follow the general spatial patterns of topographic convergence. However, spatial controls on the timing, intensity, and quantity of snowmelt and controls on vertical versus lateral flux partitioning in the soil overwhelm the influence of topographic convergence on runoff patterns during early spring freshet periods. The study findings suggest that various topographic indices and topography-based rainfall runoff models would not likely be good predictors of runoff patterns in snowmelt-dominated montane catchments during early phases of the spring freshet, but would increase in importance as the freshet and post-freshet periods proceed.