Effects of macro-pores on water flow in coastal subsurface drainage systems

Xin, Pei, Yu, Xiayang, Lu, Chunhui and Li, Ling (2016) Effects of macro-pores on water flow in coastal subsurface drainage systems. Advances in Water Resources, 87 56-67. doi:10.1016/j.advwatres.2015.11.007


Author Xin, Pei
Yu, Xiayang
Lu, Chunhui
Li, Ling
Title Effects of macro-pores on water flow in coastal subsurface drainage systems
Journal name Advances in Water Resources   Check publisher's open access policy
ISSN 0309-1708
1872-9657
Publication date 2016-01
Year available 2015
Sub-type Article (original research)
DOI 10.1016/j.advwatres.2015.11.007
Open Access Status Not Open Access
Volume 87
Start page 56
End page 67
Total pages 12
Place of publication Kidlington, Oxford, United Kingdom
Publisher Pergamon Press
Collection year 2016
Language eng
Abstract Leaching through subsurface drainage systems has been widely adopted to ameliorate saline soils. The application of this method to remove salt from reclaimed lands in the coastal zone, however, may be impacted by macro-pores such as crab burrows, which are commonly distributed in the soils. We developed a three-dimensional model to investigate water flow in subsurface drainage systems affected by macro-pores distributed deterministically and randomly through Monte Carlo simulations. The results showed that, for subsurface drainage systems under the condition of continuous surface ponding, macro-pores increased the hydraulic head in the deep soil, which in turn reduced the hydraulic gradient between the surface and deep soil. As a consequence, water infiltration across the soil surface was inhibited. Since salt transport in the soil is dominated by advection, the flow simulation results indicated that macro-pores decreased the efficiency of salt leaching by one order of magnitude, in terms of both the elapsed time and the amount of water required to remove salt over the designed soil leaching depth (0.6 m). The reduction of the leaching efficiency was even greater in drainage systems with a layered soil stratigraphy. Sensitivity analyses demonstrated that with an increased penetration depth or density of macro-pores, the leaching efficiency decreased further. The revealed impact of macro-pores on water flow represents a significant shortcoming of the salt leaching technique when applied to coastal saline soils. Future designs of soil amelioration schemes in the coastal zone should consider and aim to minimize the bypassing effect caused by macro-pores.
Keyword Drainage
Macro-pores
Preferential flow
Salt leaching
Soil heterogeneity
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: School of Civil Engineering Publications
Official 2016 Collection
 
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