Abstract
A mathematical model is developed to simulate transient unsaturated flow above a shallow watertable. The unsaturated zone, here extending from just below the phreatic level to soil surface, is schematized into a root zone and a subsoil. In the root zone the gradient of the hydraulic potential is assumed equal to zero. Vertical flow in the subsoil is described by a combination of steadystate situations corresponding to the upper and lower boundary flux, respectively. Transient flow is solved by a sequence of steadystate situations, subject to boundary flux conditions at the soil surface and from below the water table. The solution uses time increments of the order of days and is efficient in terms of computer costs.<br/>To verify the model for an actual field situation, it is linked at the upper boundary to a model for evapotranspiration and at the lower boundary to a model for twodimensional horizontal saturated flow. The resulting quasi threedimensional model is applied to a fieldsize flow problem. Results agree closely with observed watertable elevations. The composite model is further used to predict consequences of groundwater extraction.<p/>
Original language  English 

Qualification  Doctor of Philosophy 
Awarding Institution  
Supervisors/Advisors 

Award date  22 Feb 1980 
Place of Publication  Wageningen 
Publisher  
Print ISBNs  9789022007259 
Publication status  Published  1980 
Keywords
 hydraulic conductivity
 hydrodynamics
 infiltration
 models
 porous media
 simulation
 simulation models
 soil water
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de Laat, P. J. M. (1980). Model for unsaturated flow above a shallow watertable, applied to a regional subsurface flow problem. Pudoc, Centre for Agricultural Publishing and Documentation. https://edepot.wur.nl/211298