A Transient Drainage Equation by Incorporating the Variable Drainable Porosity Function and the Unsaturated Zone Flow Contribution

  • Ammar Yousfi
  • Mohamed MecherguiEmail author
Conference paper
Part of the Advances in Science, Technology & Innovation book series (ASTI)


Transient drainage equations presented earlier neglect the unsaturated flow above the water-table and assume constant drainable porosity. In this paper, a solution for the drainage problem is developed; it takes the unsaturated flow towards the drain into account and considers a variable drainable porosity. The solution is based on the spatial integration of the two-dimensional Richards Equation. The resulting integrated model is first simplified by applying Dupuit-Forchheimer (DF) theory and assuming a hydrostatic pressure distribution above the water-table, and then twice spatially integrated, yielding to a nonlinear differential equation for predicting the fall of the midway water-table height. With respect to drainage design, the developed equation, not presented before, provides a new method for designing subsurface drainage under transient conditions.


Transient conditions Unsaturated zone Variable drainable porosity Water-table Drainage equation 


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© Springer Nature Switzerland AG 2019

Authors and Affiliations

  1. 1.Institut National Agronomique de TunisTunisTunisia

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