Headwater hyporheic zones in a warming Arctic climate: An assessment of hyporheic dynamics across distinct geomorphic and permafrost conditions.

摘要

Hyporheic zones are important components of stream ecosystems because they significantly influence the hydrologic and biogeochemical processes. This study describes how geomorphology and changes in the sub-stream active-layer (zone of seasonal permafrost thaw and refreeze) control the dynamics of hyporheic zones and transient storage in arctic headwater streams. This investigation determined that the transient storage characteristics of all study streams was primarily controlled by the surface discharge and, to a much lesser effect, changes in the active-layer thickness, and that independent of channel morphology, stream power is a metric capable of predicting components of stream transient storage. Furthermore, hyporheic numerical groundwater flow modeling showed that channel morphology dictates the potential extent of hyporheic exchange, and that the thickness of active-layers can only constrain hyporheic flowpaths until a threshold thickness condition is achieved under which permafrost no longer interacts with surface waters.