Evaluating parameter estimation techniques applied in vadose zone modeling

The paper discusses vadose zone parameter estimation techniques that may be used in lieu of measured parameter values. In particular, two different data bases that provide generic parameter estimates are reviewed. The effects of parameter variability on vadose zone NAPL flow are illustrated through usage of the Kinematic Oily Pollutant Transport (KOPT) model. The model simulated a laboratory experiment where gasoline was released into a one-meter long chromatography column. The model input parameter were measured, and the position of the leading edge of the gasoline was recorded as a function of time from the experiment. Simulations that use measured or tabulated parameter sets were compared with the experimental data, which represents the correct response of the system to the gasoline input. To assess the impact of using tabulated parameters Monte Carlo simulations were performed using correlated parameter sets generated from the tabulations. These results show that wide distributions of the parameters are required to capture likely variability in input parameter values.