Desalinisation by zone leaching: laboratory investigations in a model sand-tank

摘要

We report a laboratory study in a model sand-tank to investigate improvements using partial ponding over the common method of leaching salts from soils by flooding the entire area above equally spaced subsurface drains. The physical basis of the theory developed by E. G. Youngs and P. B. Leeds-Harrison was demonstrated in the model. We traced the streamline patterns for complete ponding and 3 situations of partial ponding of the soil surface to demonstrate the flow paths. We also leached saline water, initially uniformly distributed in the sand, with sweet water and recorded the breakthrough curves of the leaching water for the same situations of complete and partial ponding. The results demonstrate that partial ponding is more effective than complete ponding in that it requires less time to carry solute towards the drain and saves water of good quality needed to leach salts through drains. They also confirm the theoretical findings that more uniform leaching with less water can be achieved by constraining the infiltrating area with bunds, initially flooding only the region midway between the drains and then progressively increasing the flooded area until the entire surface above the drains is ponded