Alberto Losada

Operation diagrams for irrigation management

Abstract A critical index for assessment of irrigation performance is the application efficiency Ra, defined by the ratio of net application Hn to the gross application diverted into the field Hb. A second critical index is the deficit coefficient Cd, defined as the ratio of the root zone deficit following irrigation, Hd, to the root zone requirement, Hr. Computer programs are now available which can adequately simulate the behavior of surface flow and infiltration as a function of inflow rate q0 and application time tar. They are useful to study surface irrigation techniques applied on a given field. If the characteristics of infiltration and the field geometry are known, then computer programs based on Saint Venant equations can be used to simulate irrigation performance. Results of such simulations are shown as characteristics diagrams of Cd and Ra on a field of tar and q0. The data sets were also used to plot curves of constant Ra and Hr for fixed values of Cd. The curves show the optimum combination of inflow rate and time to provide reasonable irrigation efficiencies. Means are also available to describe water application from a sprinkler system as a function of statistical parameters. A normal distribution function is assumed to simulate water applied onto the field. Results are shown as characteristics diagrams which represent Ra and Cd as a function of Christiansen uniformity coefficient Cu and the H b H r ratio.