Submitted to: Journal of Irrigation and Drainage Engineering
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/5/2009
Publication Date: 10/1/2009
Citation: Clemmens, A.J., Bautista, E. 2009. Toward physically based estimation of surface irrigation infiltration. Journal of Irrigation and Drainage Engineering. 135(5):588-596.
Interpretive Summary: It is possible to improve the performance of surface irrigation and thus, conserve water through improvements in design and operation. Infiltration is an important process that limits what improvements are possible. Infiltration conditions under surface irrigation are difficult to predict from soil physics. Data from observation of irrigation events are used to infer infiltration. This paper suggests a method for adjusting the soil physical parameters and applying an empirical adjustment in order to match observed infiltration. The nature of the theoretical adjustment also suggest a simple method for adjusting empirical infiltration equations. This information should be useful to irrigation farmers, the Natural Resources Conservation Service, extension specialists, and agricultural consultants.
Technical Abstract: Irrigation practitioners continue to use empirical infiltration equations. Theoretical infiltration equations are currently not capable of capturing surface irrigation infiltration behaviour, particularly at short times. An example is shown where the Green-Ampt equation can be adjusted to match field “average” infiltration conditions by altering the soil physical properties. For finer textured soils, a time off-set is proposed for adjusting the Green-Ampt equation to account for cracking and soil consolidation upon wetting. This results in a non-zero infiltration amount at time zero. Applying this concept to more empirical infiltration equations suggests the addition of a constant infiltration amount, c in mm, to the Philip equation. This is the same as a Modified Kostiakov equation with an exponent, a = ½, and addition of the c term. It is shown that the two point method can be solved for c and the Kostiakov constant k, rather than k and a, with similar results. This may help avoid some of the previously-reported problems of extrapolating the infiltration curve estimated during advance to later phases of the irrigation.