Analysis of furrow irrigation uniformity as affected by furrow spacing.

Abstract

This research examines the effects of furrow spacing on irrigation uniformity and efficiency. Laboratory and field experiments were conducted to obtain information on soil physical characteristics, furrow infiltration and water advance data in order to validate the theoretical results. A furrow infiltration model based on Richards' equation and a finite element technique is developed and used to predict infiltrated depths in the transverse and longitudinal directions relative to the furrow centerline and furrow inlet, respectively. The model predicted measured furrow infiltration in the field from the third irrigation but failed to do so for the first and second irrigations. Simulations of furrow irrigation in a hypothetical soil with various furrow spacings showed that cumulative infiltration is not affected by furrow spacing until the lateral wetting front reaches the imaginary vertical boundary located midway between two furrows. An analysis of uniformity and efficiency from predicted water distribution profiles from field irrigated furrows are conclusive in that the use of longitudinal water distribution profile alone is not enough to assess the performance of furrow irrigation. The transverse distribution of infiltrated depths which is a function of furrow spacing must be included in the analysis.