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

摘要

The role of spatial variability in water inputs on runoff dynamics hasgenerally not received as much research attention as topography and soils;however, the influence of topography and forest cover on snow surface energyexchanges can result in asynchronous snowmelt throughout a catchment,complicating the space–time patterns of runoff generation. This studyinvestigates temporal variation in the relative importance of spatialcontrols on the occurrence, duration, and timing of shallow groundwaterresponse, utilizing a highly distributed monitoring network in asnowmelt-dominated montane catchment in western Canada. The study findingsindicate that deep-soil hydraulic conductivity is a first-order control onthe spatial distribution of sites that generate shallow groundwater responseversus sites that experience only deep percolation. Upslope contributing areaand slope gradient are first-order controls on the duration of groundwaterresponse during peak-flow, recession-flow, and low-flow periods. Shallowrunoff response areas expand and contract throughout these periods and followthe general spatial patterns of topographic convergence. However, spatialcontrols on the timing, intensity, and quantity of snowmelt and controls onvertical versus lateral flux partitioning in the soil overwhelm the influenceof topographic convergence on runoff patterns during early spring freshetperiods. The study findings suggest that various topographic indices andtopography-based rainfall runoff models would not likely be good predictorsof runoff patterns in snowmelt-dominated montane catchments during earlyphases of the spring freshet, but would increase in importance as the freshetand post-freshet periods proceed.