Minimum Water Loss Canal Section

Abstract

An irrigation canal may be an unlined canal or a lined canal. The loss of water due to seepage and evaporation from canals constitutes a substantial part of the available water. The seepage loss results not only in depleted freshwater resources but also causes water logging, salinization, groundwater contamination, and health hazards. To minimize seepage and to transport water efficiently, lined canals were envisaged. A perfect lining would prevent all the seepage loss, but canal lining deteriorates with time. The thickness of the lining material is small and cracks may develop anywhere on the perimeter. The seepage from a canal with cracked lining is likely to approach the quantity of seepage from an unlined canal. The quantity of seepage is affected by the presence of a drainage layer. This chapter deals with the design of canal sections considering seepage and evaporation water losses for triangular, rectangular, trapezoidal, parabolic, and power law canals. The chapter also includes special cases, for example, minimum seepage loss sections without drainage layer and minimum seepage loss sections with drainage layer at shallow depth. The resultant explicit equations for the design variables of minimum water loss sections have been obtained using nonlinear optimization technique. The proposed equations along with tabulated section shape parameters facilitate easy design of the minimum water loss section and computation of water loss from the section without going through the conventional and cumbersome trial and error method. Design examples have been included to demonstrate the simplicity of the method.