Screening and understanding the importance of soil hydrology related factors in a SVAT scheme
2006
Metselaar, K. | van Dam, J.C. | Feddes, R.A.
In this report a simulation experiment using a hydrological water balance model is executed. Using a little simulation runs as possible, the experiment is set up to estimate the main effect of an individual variable on different water balance terms given simultaneous variation in all other factors. The ranking of the variables in terms of their relative effect suggests a priority in the processes to be incorporated in new versions of a SVAT scheme. The experiment was set up to analyze the effects of 13 variables. Variables varied are leaf area index and its time course, root depth and its time course; profile discretization, description of the soil hydraulic characteristics (Hornberger-Clapp vs. van Genuchten), stoniness, the reduction of vegetation transpiration as a function of moisture content or as a function of soil matric head, the point at which reduction of transpiration occurs, and the lower boundary condition of the soil (lateral drainage at 1 m and an impermeable layer at the bottom of the soil profile or free drainage at the bottom of the profile). Results show that the choice of the lower boundary condition, the maximum root depth, and whether or not leaf area index is a function of time, have a strong effect on yearly and monthly evapotranspiration.
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