Analysis of seepage from a triangular furrow considering soil capillarity using inverse hodograph and conformal mapping technique

Abstract

Capillary action facilitates supply of irrigation water to root zone in furrow ridge, though capillarity enhances seepage loss from a furrow. In this study, seepage loss from a triangular furrow has been determined analytically considering soil capillarity using inverse hodograph and conformal mapping technique. Loci of the upper boundary of saturation in the furrow ridge have been located for various side slopes of ridge, and bubbling pressure or air exit pressure heads of subsoil. This study would help to determine the appropriate top width of the ridge between parallel furrows, furrow spacing and required free board of a triangular furrow. From the study, it is found that: (i) dimensionless quantity of seepage from unit length of a furrow, i.e. ratio of seepage loss to hydraulic conductivity times the maximum depth of water in the furrow, as well as the maximum vertical rise in furrow ridge above water level in furrow due to capillary action varies non-linearly with the dimensionless bubbling pressure head; (ii) the height of capillary rise along the slopes under hydrodynamic condition is always less than height of static capillary rise. (iii) The analysis and results, presented in this study, would facilitate design of parallel triangular furrow system.