Submitted to: Journal of Hydrology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 2/20/2008
Publication Date: 8/1/2008
Citation: Santhi, C., Kannan, N., Arnold, J.G., DiLuzio, M. 2008. Spatial calibration and temporal validation of flow for regional scale hydrologic modeling. Journal of Hydrology. 44(4):829-846. Interpretive Summary: As concerns about managing water supplies and water quality in the U.S. grow, models are being increasingly used for planning and management of our water resources. Before the models can be used to analyze various planning scenarios, they must be calibrated and compared to measured data. In this study, a novel approach was developed to calibrate models to accurately reproduce all the components of the water balance at multiple locations within a river basin. This gives water resource planners confidence in model output and in their management plans.
Technical Abstract: Physically based regional scale hydrologic modeling is gaining importance for planning and management of water resources. Calibration and validation of such regional scale model is necessary before applying it for scenario assessment. However, in most regional scale hydrologic modeling, flow validation is performed at the river basin outlet without accounting for spatial variations in hydrological parameters within the subunits. In this study, we calibrated the model to capture the spatial variations in runoff at subwatershed level to assure local water balance, and validated the streamflow at key gauging stations along the river to assure temporal variability. Ohio and Arkansas-White-Red River Basins of the United States were modeled using Soil and Water Assessment Tool (SWAT) for the period from 1961 to 1990. R2 values of average annual runoff at subwatersheds were 0.78 and 0.99 for the Ohio and Arkansas Basins. Observed and simulated annual and monthly stream flow from 1961 to 1990 is used for temporal validation at the gages. R2 values estimated were greater than 0.6. In summary, spatially distributed calibration at subwatersheds and temporal validation at the stream gages accounted for the spatial and temporal hydrological patterns reasonably well in the two river basins. This study highlights the importance of spatially distributed calibration and validation in large river basins.