| An event-based, kinematic, infiltration-excess, distributed rainfall-runoff model was developed to acknowledge and account for the spatial variability and uncertainty of several parameters relevant to storm surface runoff production and surface flow. The model is compatible with raster Geographic Information Systems (GIS) and spatially and temporally varied rainfall data. Principal raster data inputs include hydrography data derived from a digital elevation model, soil texture, forest type, forest density, lakes, reservoirs, land use and land cover, and impervious regions within a basin. These GIS data sets are used to support computations related to spatially-varied interception, accounting of input rainfall to lakes and reservoirs and routing into reservoirs, spatially-varied infiltration, kinematic-wave overland flow routing, channel losses, and kinematic-wave channel flow routing. The main model outputs include a volume summary, discharge hydrographs for each sub-basin as well as for the main basin outlet, and raster maps of various variables; such as, cumulative infiltration and excess-rainfall.; Monte Carlo simulation and a likelihood measure are utilized to calibrate the model; allowing for a range of possible system responses from the calibrated model. The model structure supports a meaningful distributed model calibration, and allows for the investigation of uncertainty in rainfall-runoff modeling. Using rain gauge adjusted radar-rainfall estimates, the model was applied and evaluated to a limited number of historical events for two watersheds within the Denver Urban Drainage and Flood Control District (UDFCD) that contain mixed land use classifications. For the events considered, the 95% uncertainty bounds obtained from the model envelop almost all observed responses, not only at the main basin outlets, but also at a location internal to one of the two basins, suggesting an acceptable model structure. While based on a limited number of Monte Carlo simulations and considered events, Nash and Sutcliffe efficiency score ranges, based on a comparison of observed and simulated hydrographs, of –0.19–0.95/–0.75–0.81 were obtained from the calibrated models for the two basins. The hydraulic conductivity of the soil was the single model parameter most relevant to reducing runoff volume uncertainty. Uncertainties in initial conditions and rainfall estimates were also shown to play a significant role in model uncertainty. |
