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Submitted to: Geophysical Union Canadian
Publication Type: Abstract Only Publication Acceptance Date: 4/2/2006 Publication Date: 5/14/2006 Citation: Seyfried, M.S., Murdock, M.D., 2006. Subsurface Processes Affecting Cold Season Streamflow Generation. Proceedings of the Canadian Geophysical Union, May 14-17,2006, Banff, Canada. p. 119 Interpretive Summary: Technical Abstract: The amount and timing of snowmelt-generated streamflow greatly affects the management of water resources in the western USA and Canada. Subsurface processes that deliver water to streams during snowmelt are somewhat different from those that occur during rainfall. In this study we document some of these processes and describe their impact on streamflow generation. Snow drastically affects the soil temperature regime by providing insulation. We show how insufficient snow cover may result in soil freezing, which radically affects soil hydraulic properties and causes upward soil water movement. In addition, we show that the insulating properties of snow allow soil heat flux to thaw frozen soil. In contrast to many rainfall events, the periodic, modulated nature of snowmelt inputs means that water inputs from snow are often into nearly saturated soil. The result is that resistive or capillary barriers are often not critical, as they may be during rainfall event, and streamflow response can be very rapid, but almost entirely via the subsurface. We illustrate this process from the snow surface through the soil to the groundwater and streamflow. Another major difference between snowmelt and rainfall inputs is the spatial and temporal variability of snowmelt inputs. However, once the subsurface flow network is “charged” with water, flow response is so rapid that spatial variability effects on streamflow generation appear to be small. When snow cover has melted in the spring, the network is rapidly disrupted as an upward soil water potential gradient develops . |
