Identifying Thresholds for Water Storage and Transmission In Montane Watersheds From the Soil up.

Snowmelt and the fate of water in the soils of montane watersheds are the first steps in the hydrologic cycle where water enters a highly managed system.  Concerns over changes in regional climate and increasing demands for water quantity and quality pose new challenges, and water supplies may be affected by increased fire frequency, reduced snowpacks, earlier and more rapid snowmelt, and higher intensity precipitation coupled with increasing demands for water quantity and quality.  Because complex heterogeneities in snow cover, soil texture, structure and ecotones exist that are involved in the initiation, transmission and temporal availability of water, modeling soil-water dynamics lacks determinate  parameterizations at the watershed scale, and approximating functions based on large-scale responses are established.  Experimental evidence suggests that preferential pathways establish that form the major conduit for the infiltration flux and that soil and ecosystem heterogeneities play a larger role than assumed by conventional watershed-scale models.  Our objectives were to quantify thresholds in partitioning water in montane systems and changes in soil-water storage considering dynamic interactions between land/snow surface and vadose zone resulting in the channelized infiltration of water.  We used integrated multichannel measurement technologies to characterize the seasonal soil-water dynamics using time-lapse electrical resistivity tomography (ERT), and used the improved characterization of water distribution and transport as the necessary first step towards incorporation of point- to landscape scale hydrodynamic processes. We believe that proper understanding of soil-water fluxes across scales is essential to interpretation and modeling of complex and heterogeneous flow and transport behavior linked to regional climate forcings. Future needs to protect ecosystems and better manage and predict water availability and quality necessitate threshold-driven non-linear response predictions of water supplies.