Aspect control of water movement on hillslopes near the rain-snow transition of the Colorado Front Range

作者：Hinckley Eve Lyn S^*; Ebel Brian A; Barnes Rebecca T; Anderson Robert S; Williams Mark W; Anderson Suzanne P

来源：HYDROLOGICAL PROCESSES, 2014, 28(1): 74-85.

DOI：10.1002/hyp.9549

• lithium bromide tracer
• slope aspect
• temperature-index model
• Hydrus-1D
• critical zone
• Boulder Creek Critical Zone Observatory

In the Colorado Front Range, forested catchments near the rain-snow transition are likely to experience changes in snowmelt delivery and subsurface water transport with climate warming and associated shifts in precipitation patterns. Snowpack dynamics are strongly affected by aspect: Lodgepole pine forested north-facing slopes develop a seasonal snowpack, whereas Ponderosa pine-dotted south-facing slopes experience intermittent snow accumulation throughout winter and spring. We tested the degree to which these contrasting water input patterns cause different near-surface hydrologic response on north-facing and south-facing hillslopes during the snowmelt period. During spring snowmelt, we applied lithium bromide (LiBr) tracer to instrumented plots along a north-south catchment transect. Bromide broke through immediately at 10- and 30-cm depths on the north-facing slope and was transported out of soil waters within 40days. On the south-facing slope, Br- was transported to significant depths only during spring storms and remained above the detection limit throughout the study. Modelling of unsaturated zone hydrologic response using Hydrus-1D corroborated these aspect-driven differences in subsurface transport. Our multiple lines of evidence suggest that north-facing slopes are dominated by connected flow through the soil matrix, whereas south-facing slope soils experience brief periods of rapid vertical transport following snowmelt events and are drier overall than north-facing slopes. These differences in hydrologic response were largely a function of energy-driven differences in water supply, emphasizing the importance of aspect and climate forcing when considering contributions of water and solutes to streamflow in catchments near the snow line.

• 出版日期2014-1-1