Submitted to: Journal of Irrigation and Drainage Engineering
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/27/2009
Publication Date: 10/1/2009
Citation: Bautista, E., Clemmens, A.J., Strelkoff, T. 2009. Optimal and postirrigation volume balance infiltration parameter estimates for basin irrigation. Journal of Irrigation and Drainage Engineering. 135(5):579-587.
Interpretive Summary: Engineering analysis of surface irrigation systems requires reasonable predictions of infiltration as a function of time. This study compares two different approaches for characterizing a field's infiltration behavior from irrigation evaluation data. One method uses surface volume data measured at multiple times during the irrigation event, and is presumed to yield the most accurate results. It is used primarily for research applications because surface volume measurements are difficult and costly, and because it is computationally intensive. The other method, commonly used by irrigation professionals, uses post-irrigation data, requires no surface volume measurements, and is computationally simpler. The analysis shows that the simpler method can generate results comparable to those obtained with the more sophisticated method, if the analysis is supported by modern hydraulic simulation. The analysis also shows that the resulting information can be used to optimize management, despite uncertainties of the results. Such findings can help NRCS irrigation specialists and other irrigation professionals improve their strategies for evaluating infiltration information at the field level and to develop design and management recommendations from such information.
Technical Abstract: Engineering analysis of surface irrigation systems requires a reasonably accurate description of a field's infiltration characteristics. Optimal estimation methods have been proposed for this purpose. These methods pose multiple volume balance equation at various stages of an irrigation event and have been shown to produce accurate results. They have the disadvantage of requiring surface volume determinations, which may be difficult to obtain in practice under many field conditions. This study contrasts infiltration solutions from optimal and simpler post-irrigation volume balance method and examines the implications of those solutions on the performance of management strategies. There is little benefit in using optimization over post-irrigation volume balance due to the non-uniqueness of solutions, uncertainties of inputs required by the estimation procedures, and the natural variability of soil infiltration properties. Results show that critical to characterizing the infiltration properties for an irrigation system is determining the time needed to infiltrate a target depth. For the type of systems considered here, management can be optimized based on this concept, even if the infiltration function parameter values are uncertain.