ABSTRACT
We have used a macroscale hydrological model (Variable Infiltration Capacity [VIC] 3-Layer) implemented to understand the water and energy balance for over a period of 50 years (1950 to 1999) for the Upper Mississippi River basin, and also evaluated in detail the performance in the complete spectrum of droughts and floods. Simulations have been carried out between January 1950 and December 1999 at daily time-step and 1/8º spatial resolution for the water budget and at hourly time-step and 1º spatial resolution for the energy balance. The water balance simulations show seasonal variability of soil moisture, and more importantly the variability of soil moisture during the period of flood (1993) and drought (1988). Model-simulated soil moistures for the state of Illinois were validated with measured soil moisture data from the Illinois State Water Survey. The model-simulated streamflows were compared with the U.S. Geological Survey (USGS) measured stream-gauge observations at the basin outlet at the Mississippi River at Grafton, IL and the Illinois River at Valley City, IL, which showed a 15% relative bias. Model validations for the hourly surface temperature were performed for a period of 20 years (1980 to 1999) by comparison with TIROS Operational Vertical Sounder (TOVS) surface temperature. These comparisons show a good correlation coefficient of around 0.8 with a low bias of 1 to 2K and a root mean squared difference of 6 to 7K. The model-simulated deep soil moistures have been analyzed to understand the spatial and temporal variability of droughts and floods.
