Applications
Application of the WetSpa model to the Distributed Hydrologic Model Intercomparison Project (DMIP)
The department of Hydrology and Hydraulic Engineering is participating in the second phase of the
Distributed Model Intercomparison Project (DMIP II) of the Hydrology Lab of the National Weather Service,
Office of Hydrologic Development (NWS-OHD), USA. This project intends to evaluate the capabilities of
existing distributed hydrologic models forced with operational quality radar-based precipitation data.
In this PhD research, the WetSpa model is applied to simulate runoff in five USA watersheds of the DMIP project.
The model implementation is based on 30 m spatial resolution and one-hour time step. Rainfall inputs
are derived from NEXRAD (radar). The distributed model parameters are based on an extensive database of
watershed characteristics available for the region, including digital maps of DEM, soil type, and land use.
The model is calibrated and validated on part of the river flow records for each basin and applied to the
smaller interior watersheds not used in calibration to assess the model performance in ungaged basins.
The model performance is assessed by calculating the Nash-Sutcliffe efficiency (NS), where a value of 1 represents
a perfect fit. The statistics improve significantly with calibration of the global model parameters but even
for uncalibrated simulations, the physically-based WetSpa model reproduces flow rates of acceptable accuracy
for most cases. The statistics show that NS is 0.75 for the Elk River near Tiff City, and 0.83 for the
Illinois River near Watts for the calibration periods. With the exception of Blue River basin, the overall
statistics during the validation period remain good (NS varies from 0.67 to 0.82), indicating that the model is
able to simulate the relevant hydrologic processes in the basins accurately. A potential future research for
WetSpa development is to validate the model in watersheds where snow accumulation and ablation is significant
(e.g. DMIP II California Sierra Nevada watersheds).