Resumo

ZAVALA, Manuel; SAUCEDO, Heber  e  FUENTES, Carlos. Computer program to analyze the water dynamics in subsurface agricultural drainage systems. Agrociencia [online]. 2014, vol.48, n.1, pp.71-85. ISSN 2521-9766.

The analysis of agricultural drainage requires a computer tool to help a user describe the changes in the shallow water table and the drainage flow, taking into account soil properties, physical characteristics and spatial disposition of drains and the vertical rates of recharge or discharge of the aquifer (infiltration or evapotranspiration). In this study, the computer program with graphic interface called DRENAS was developed, which simulates the hydraulic functioning of subsurface drainage systems; its main calculation module has a numerical solution to the one-dimensional Boussinesq equation for unconfined aquifers, considering the storage coefficient of the aquifer as a function of the hydraulic head and representing the vertical recharge as a function of time. In this module, non-linear relationships between the drainage flow and the hydraulic head on the drain can be used, known as fractal radiation and convex radiation boundary conditions. The program was complemented by including a database with information about soil properties and a calculation module with simplified analytical solutions for agricultural drainage. The module of the numerical solution was validated, first, by comparing its results with those obtained when applying the analytical solution for the transitory regime that is derived by assuming linear radiation boundary conditions and considering the transmissivity and storage coefficient of the unconfined aquifer as constants; then, it was validated by considering data from drained water depth measured in an experimental system. Both validations showed the ability of the model to describe the change of the water table and the volume drained for different conditions of drain design (maximum differences 0.025% and 0.48 cm, respectively). Therefore, the user can assume that the results described by DRENAS are reliable, if the scenarios analyzed fulfill the hypothesis for which it was developed.

Palavras-chave : non-linear radiation; drainage flow; Boussinesq equation; unconfined aquifer; numerical solution; graphic interface.

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