The development of guidelines for surface irrigation in areas with variable infiltration

The efficiency of surface irrigation is a function of the field design, infiltration characteristics of the soil, and the irrigation management practices. Seventeen surface irrigations were monitored on a single Burdekin Delta farm throughout the 1994-95 season. Significant (P<0.05) spatial and temporal variability in the infiltration functions was observed throughout the season. Simulations of irrigation performance conducted using the SIRMOD model and the average infiltration characteristic for the site, indicated that application efficiencies could be increased from the average 41 % achieved in the field trials to 71%, simply by using a more appropriate rate of water application and time to cut-off. The application of real-time control management practices was found to potentially increase application efficiency to 93%. However, the variability in infiltration was also found to substantially affect the selection of appropriate surface irrigation design and management guidelines. Charts which illustrate the effect of infiltration variability on irrigation performance are presented and the possible use of these charts as design aids is discussed.