Fig. 4: Conceptual models of streamflow generation in mountain catchments.

Most common conceptual and numerical models of mountain hydrology include a shallow active soil layer (~1 m in depth) capable of storing 20–50 cm of water overlying bedrock with minimal storage (a). As shallow soils approach saturation, precipitation or snowmelt is routed quickly to surface water. b In contrast, our data support emerging conceptual models of mountain hydrology that include large saprolite and bedrock water storage underlying these soils. Our age dating of baseflow and snowmelt runoff suggests that an order of magnitude more of actively cycling water is stored in these headwater catchments.