The use of mathematical models facilitates the calculation of the uniformity and efficiency parameters of irrigation systems and, thus, its utilization should be encouraged. This work had as its objectives the proposal of the use of a polynomial function for evaluating irrigation systems and to develop the mathematical relationships for calculating the main indicators for measuring irrigation performance, utilizing this function. In order to define the model to be proposed and to verify its suitability, comparisons were carried out among polynomial functions of various degrees against the Silva's potential model, utilizing data from 91 cases of irrigation system evaluations. The selection of the most adequate polynomial model was made by comparing adjusted curves to the cumulative frequency distribution of the sum of square errors that were obtained after adjusting the models to each set of measured water application data. The results showed that the fifth degree polynomial function is recommended to describe the applied water distribution from irrigation systems and it can be used to derive mathematical expressions for calculating the corresponding performance measures.
applied water; uniformity; efficiency; water distribution
