ABSTRACT
The quantification of the performance of earth covers has been largely determined through the use of test plots as well as numerical modeling. Such numerical models are run with the use of complex climatological data and unsaturated soil property functions. The input information is then used by the finite element solvers to determine vertical flow rates and, ultimately, long-term percolation rates through the earth cover. Calculations are generally complicated by the fact that the infiltration into a dry soil is one of the more complex types of numerical modeling scenarios. The challenge occurs largely because of the non-linearities present in the unsaturated soil properties. These non-linearities becomes part of the numerical model which must run for 1, 10, or 50 years. This paper examines the numerical difficulties associated with these calculations and examines the impact of small numerical issues over long time periods. In particular, the role of mesh density as it is related to the accuracy of water balance calculations is examined.
