APPLICABILITY OF SIMPLIFIED UNSATURATED FLOW MODELS UNDER LARGE UNCERTAINTY IN HYDRAULIC PROPERTIES

Abstract

Moisture movement through unsaturated zone is an important topic in groundwater hydrology, soil science, agricultural engineering and environmental engineering. The flow through unsaturated zone is usually analyzed by solving Richrad's equation (1931). For the solution of Richard's equation, the functional relationships between soil hydraulic properties (K, 0 and yr) are needed which are generally of a nonlinear form. In addition, these relationships, estimated from field measured data, usually show large variability' because of measurement errors and natural spatial heterogeneity exhibited by many field soils. A probabilistic approach is often employed to account for this uncertainty in parameters where by the coefficients in the resulting partial differential equations are treated as random quantities. The present study is aimed at evaluating the errors when simplified unsaturated solution based on simple forms of the hydraulic properties are used rather than nonlinear and numerically complicated model. The, objective of the present study is to. evaluate the applicability of simplified unsaturated flow solution based on simple forms of hydraulic properties in place of numerical model. To compare models, scaled error definitions (Govindaraju et al., 1992) are introduced and are expressed as- a percentage of the saturated moisture content of the soil at the constant head boundary condition at top.