Upscaling hillslope-scale subsurface flow to inform a catchment-scale storage-discharge relationship

The catchment-scale relationship between subsurface storage and outflow (Q=f(S)) is often used to characterize the recession response of a watershed. While typically identified via investigation of hydrograph data, the link between this response shape and the geomorphological/geological characteristics of the watershed is poorly understood. This work focuses on the power-law Q=f(S) relationship generated by the subsurface stormflow (SSF) response of a landscape comprised of hundreds of individual hillslopes in response to a recharge event. This work builds on previous insights into hillslope-scale SSF modelling to directly link the coefficients of the Q=f(S) relationship to (1) the distribution of hillslope properties in the catchment, and (2) the magnitude and recent history of recharge applied to the landscape. All hillslopes are derived directly from remote sensing elevation data, and are solved numerically using the full, non-linear Hillslope Storage Boussinesq Equation. The Q=f(S) behaviour of a large suite of catchments (n >= 50) is evaluated, and the hypothesis that the Q=f(S) coefficients can be derived directly from the distribution of hillslope properties and recharge data is tested.