Effects of macro-pores on water flow in coastal subsurface drainage systems |
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| Institution: | 1. State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering, Hohai University, Nanjing, China;2. Monash Water for Liveability, Civil Engineering Department, Monash University, Victoria, Australia;3. School of Civil Engineering, The University of Queensland, Queensland, Australia;1. Department of Fluid Mechanics, CSIC-Universidad de Zaragoza, LIFTEC, Spain;2. Department of Geography, Vancouver Campus, University of British Columbia, Canada;1. Environmental Science R&D Unit, Science Division, West Region, Meteorological Service of Canada, Environment Canada, Canada\n;2. Environmental Science and Geography Program, University of Alaska Southeast, United States\n;3. Department of Land, Air and Water Resources, University of California, Davis, 1 Shields Avenue, PES 1110, Davis, CA 95616, United States\n;4. Alaska Science Center, US Geological Survey, United States;1. IRIS, P.O. Box 8046, Stavanger N-4068, Norway;2. National IOR Centre of Norway, Stavanger N-4036, Norway;3. University of Stavanger, Stavanger N-4036, Norway;4. Norwegian Petroleum Directorate, P.O. Box 600, Stavanger N-4003, Norway;1. State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering, Hohai University, Nanjing, China;2. Yangtze Institute for Conservation and Development, Hohai University, Nanjing, China;3. School of Engineering, Westlake University, Hangzhou, China;4. Laboratoire de technologie écologique (ECOL), Institut d''ingénierie de l''environnement (IIE), Faculté de l''environnement naturel, architectural et construit (ENAC), Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland;1. State Key Laboratory of Water Resources and Hydropower Engineering Science, Wuhan University, Wuhan 430072, China;2. Department of Sustainable Development, Environmental Science and Engineering, KTH Royal Institute of Technology, Stockholm 10044, Sweden;3. State Key Laboratory of Hydraulics and Mountain River Engineering, College of Water Resource & Hydropower, Sichuan University, 610065 Chengdu, Sichuan, China;4. Center for Permafrost, Department of Geosciences and Natural Resource Management, University of Copenhagen, Copenhagen 1350, Denmark |
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| 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. |
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