Hydraulics of a Partially Penetrating Ditch Drainage System in a Layered Soil Receiving Water from a Ponded Field

Abstract

This study deals with the development of an analytical solution for predicting seepage into an array of ditch drains dug in a three-layered soil underlain by an impervious barrier and receiving water from a ponded field of infinite extent. The solution is of a general nature and can account for partial penetration, finite width and spacing of drains, finite depth of the impervious stratum, anisotropy of individual layers, and a uniform ponding distribution at the surface of the soil. The validity of the developed solution for the single-layered situation is checked by first reducing the proposed multilayered solution to that of a single-layered one by treating the conductivity of the layers as the same and then comparing for a few flow situations the hydraulic heads as predicted by the reduced model with corresponding values obtained from the analytical and experimental works of others. A numerical check on the developed analytical model for a multilayered soil is also carried out. The study shows that flow to a multilayered ponded ditch drainage system is sensitive to the magnitude of the hydraulic conductivity as well as on the anisotropy of the constituent layers. Further, the study also corroborates the work of others that the presence of a plow sole layer in a paddy field greatly restricts the movement of seepage water through such a soil and that for such a situation considerable time may be required by a water particle to move from the surface of the field to a recipient subsurface drain in the soil.