Free-Boundary Seepage from Asymmetric Soil Channels
We present an inverse method for the study of the seepage from soil channels without lining. We give integral representations of the complex potential, velocity field, stream lines, free phreatic lines, and contour of the channel by means of Levi-Civita's function 𝜔. For different values of the Taylor coefficients of 𝜔, we calculate numerically the contour of the channel, the phreatic lines, the seepage loss, the velocity field, the stream lines, and the equipotential lines. Examples are given for various symmetric or asymmetric channels, with smooth contours or with angular points.
DESIGN OF MINIMUM SEEPAGE-LOSS NONPOLYGONAL CANAL SECTIONS
Analytical solutions exist for the problem of determination of seepage loss from polygonal sections such as a triangle, a rectangle, and a trapezoid. In this investigation, seepage from circular and exponential sections has been calculated by a finite-difference-based numerical solution of the differential equation governing the seepage flow. The phreatic boundaries of the flow domain were described in terms of two parameters that are estimated by a minimization process. Such seepage computations were performed for a large number of independent dimensionless variables of the section geometry. Subjecting the computed seepage to regression analyses explicit equations for seepage loss from canals having circular and exponential cross sections have been obtained. Using these seepage-loss equations, the design variables for minimum seepage loss of circular and exponential canal sections have been obtained. The use of the design equations has been illustrated by design examples.
Water losses from irrigation canals
Abstract This paper investigates the water losses from a canal to an aquifer. From field measurements, large losses from canals have been identified, even when the canal is lined. The reasons for these losses are investigated by performing numerical model solutions for a series of examples with different conditions at the lower boundary of the aquifer, at lateral boundaries and at the water table within the aquifer. Partial lining of a canal is shown to have little effect on the magnitude of the losses and total lining which contains defects is also ineffective. The paper emphasises the need for detailed field work into the conditions within aquifers in the vicinity of canals.