Author(s)

G. Barua & W. Alam

Abstract

An analytical solution is worked out for predicting transient seepage into a network of parallely spaced ditch drains in a homogeneous and anisotropic soil overlying an impervious barrier and receiving water from a uniformly ponded field. The distance between the adjacent drains is assumed to be the same and the level of water in all the ditches are all considered as equal in the analysis. In order that only two-dimensional flow prevails in the flow spaces in between the drains, it is further assumed in the mathematical procedure that the field is of infinite extent. The correctness of the develop model is established by performing a MODFLOW check on it for a considered ditch drainage situation. The study shows that the rate of water entry at the surface of a soil from a uniformly ponded field to the ditch drains is of a relatively better uniformity at early times of a simulation and that this uniformity gets progressively reduced with the passage of time, particularly for situations where the anisotropy ratio (it is a quotient between the horizontal and vertical saturated hydraulic conductivities of a soil) of the soil is low. Further, the transient state duration of a ponded ditch drainage scenario may be considerable if the drains are being laid in a soil having low directional conductivity values and a high anisotropy ratio, more so if the drains are being installed relatively deeper into the ground. The solution provided here is important as it can be successfully employed for designing a network of ditch drains for cleaning a salt affected soil and also in reclaiming a water-stagnated area. Keywords: analytical solution, ponded field, equally spaced ditch drains, saturated directional conductivity, specific storage, anisotropy ratio, uniform depth of ponding.

Keywords

Keywords: analytical solution, ponded field, equally spaced ditch drains, saturated directional conductivity, specific storage, anisotropy ratio, uniform depth of ponding.