This study contemplates the development of a computational model seeking to fill the principal shortcomings of the existing models, and it also accomplishes a sensitivity analysis aiming to verify the effect of the input parameters on the results obtained by application of the model. The model accounts daily for the main components of the water balance in a controled volume at half distance between two parallel drains on unitary base and a height equal to the distance between the soil surface and the soil impermeable layer, simulating the movement of the water table. Using the production functions that consider the stress caused by excess and lack of water in the root zone, this model accomplishes the economic analysis for several configurations of the drainage system, allowing for the determination of the economic spacing among drains besides informing about the economic viability of the enterprise. By sensitivity analysis it was verified that the parameters mean drain depth, horizontal soil saturated hydraulic conductivity, drainable porosity, climatic parameters, CN coefficient and the cost of the underground drain installation have a great influence on calculation of the economic drain spacing.
agricultural drainage; simulation model; economic analysis
