Modelo de simulação para racionalização do uso da água em irrigação por sulco.

Abstract

The surface irrigation systems are the most used not just in Brazil but, in the whole world mainly due to the economy of energy and its operation easiness; however, these systems present low levels of performance, usually, as a consequence of inadequate design and management. Thus, the objective of this research was to develop a tool capable to make possible the optimization of the continuous flow furrow irrigation performance, making successive simulations of the advance phase and respective prognostics of the performance parameters of the irrigation system. The simulations of the advance phase were accomplished by the kinematic-wave model implemented in this research basing in the theoretical development presented by Walker & Humpherys (1983). The methodology of Burt et al. (1997) was used to evaluate the furrow irrigation performance parameters. The proposed model was written in the programming language DELPHI 5.0 and denominated SASIS, "Software Applied to Simulation of the Surface Irrigation", and had its validation tested for different field conditions. The results demonstrated that the applied discharge had decisive influence on the performance parameters of the furrow irrigation system, in which the best performance happened for discharges close to allowable minimum values. It was verified that the field parameter that make more difficulty the optimization is the infiltration, while the length and the slope don't interfere in a decisive way, allowing the optimization be reached for a great strip of values of those parameters. It still was verified that in soils with high infiltration rates, the greatest difficulty in the optimization is to minimize the deep percolation losses, while in soils with low infiltration rates the deep percolation losses as well as the runoff losses could be easily minimized. The results of this research show the need of the optimization in the furrow irrigation systems with continuous flow, identifying although that for some field conditions high levels of performance can be reached by optimization. The model developed in this research presents effective mechanisms in the accomplishment of countless simulations, in a discharge strip understood between the minimum and the maximum allowable values, aiming to determine the relationship between discharge and water application efficiency, deep percolation and runoff rates, and consequently to optimize the performance of the furrow irrigation systems with continuous flow.