Subsurface Water Distribution from Drip Irrigation Described by Moment Analyses

Abstract

Abstract: Moment analysis techniques are applied to describe the spatialand temporal subsurface wetting patterns resulting from furrowinfiltration and redistribution. These techniques are adapted fromprevious work with drip irrigation. The water added is consideredas a“plume” with the zeroth moment representing the total volume of waterapplied to the domain. The first moments lead to the location ofthe center of the plume, and the second moments relate to the amountof spreading about the mean position. Using moments, any fractionof the applied water and its spatial extent, defined by an ellipse,can be related to a “probability” curve. Remarkably, the probabilitycurves are, for practical purposes, identical for all times and forall of the soils considered in this study. The same observation wasmade inrelation to the distribution of water under a dripper. The consistencyof the probability relationships can be exploited to pinpoint thedistribution of irrigation water under a furrow in a compact andphysically meaningful way. This approach is tested with numericallygenerated data for infiltration from furrows in three contrastingsoils. The general conclusion is that moment analysis allows a straight-forward, physically meaningful description of the general patternof moisture distribution. Potential applications of the results ofmoment analyses include improved irrigation management, formulationof the infiltration and redistribution process from a furrow in aneural network setting, and parameter estimation of the soil hydraulicproperties.