SMoRMod - A GIS-integrated rainfall-runoff model

The Soil Moisture-based Runoff Model (SMoRMod), is a cell-based rainfall-runoff model which is integrated into the GRASS (Geographic Resources Analysis Support System) Geographic Information System (GIS). The use of current GIS technology enables construction of strong physically based models that are entirely spatially referenced, within which all parameters, results, and intermediates retain their physical meaning. The model consists of soil moisture balance and runoff generation/transport submodels. The soil moisture balance submodel functions on a daily time step and provides the initial conditions for the runoff generation submodel. The latter operates with a short time step (30 min for this study) and features an infiltration function in which the incremental abstraction is derived directly from the soil moisture status. The formulation of the infiltration function accounts for both infiltration excess and saturation excess types of runoff generation. The model uses only readily available watershed characteristic data, e.g., soils, topography, and land use, and requires minimal calibration. Model results compare favorably with recorded streamflows for 77 rainstorms on the WD-38 watershed in east-central Pennsylvania. The 77 storms encompass a wide variety of rainfall amounts, rainfall intensities, and antecedent moisture conditions.