Sensitivity of Soil Moisture and Runoff Dynamics to Hydrologic Response Unit Delineations in SMART

Abstract:

A new approach of semi-distributed hydrologic modelling has been developed to reduce the computational time and effort in distributed hydrologic modelling at large catchment scales. The GIS-based semi-distributed hydrological modelling framework, SMART, delineates contiguous and topologically connected Hydrologic Response Units (HRUs) and simulates soil moisture and runoff dynamics using a 2-dimensional model based on Richards’ equation at the scale of cross sections or equivalent cross sections (ECS). Simulated fluxes from every cross section or ECS are weighted by the respective area from which the cross sections or ECSs were formulated in a first-order sub-basin. These are then aggregated to obtain catchment scale fluxes.

Herewith, we investigate the impact of HRU delineation methodology in simulating hydrologic fluxes at the catchment scale using SMART. The HRU delineation methodology consists of delineating first order sub-basins and landforms. Landforms which transfer fluxes from the upper part of a hillslope to the lower regions are delineated using topographic and geomorphologic descriptors of the catchment. However, obtaining the appropriate thresholds for landform delineation is impacted by the metric and landform delineation approach chosen by the modeller. We use variation in a number of topographic and geomorphologic descriptors of the entire catchment or groups of sub-catchments in relation to distance from the stream to assess the impact of landform delineation approach on simulated hydrologic fluxes. In addition to the spatial resolution of a digital elevation model, , three landform delineation approaches of SMART are examined. In the next step, we extend this approach to catchments with different topographic and geomorphic characteristics to find appropriate metrics for landform delineation in different settings.