engleski

Numerical simulation of water flow in tile and mole drainage systems

Tile drainage systems are sometimes not sufficient to provide favorable unsaturated conditions in therootzone. These drainage systems then need to be supplemented with an additional high conductivitymaterial in the trenches above the tiles or by implementing mole drainage. The HYDRUS (2D/3D) modelwas used to evaluate the impact of such additional measures for heavy clay soil. Three types of drainagesystems were simulated: (i) tile drains, (ii) tile drains with gravel trenches, and (iii) tile drains with graveltrenches and mole drains, using either two- dimensional (the former two systems) or three- dimensional(the latter one) transport domains. Three scenarios were considered to test the efficiency of each system:(i) time to drain an initially saturated system, (ii) high intensity rainfall, and (iii) a real case scenario.Different horizontal spacings between tile drains with or without gravel trenches were also comparedwith the system which included mole drainage. The results showed that the drainage system that includedmole drains and gravel trenches was the most efficient. This system provided the largest drainage rate, was the first to reach steady-state in the time to drain scenario, and also efficiently reduced surfacerunoff. Adding mole drains to a system with tile drains and gravel trenches resulted in a large reductionof surface runoff (75%). Simulations showed that the spacing of tile drains with or without gravel trencheswould have to be 40% or 55% smaller, respectively, in order to reproduce the same water table levels asthose observed for the drainage system with mole drains. Therefore, introducing mole drains in drainagesystems is an efficient practice for reducing waterlogging and runoff.

Tile drainage; Mole drainage; Numerical simulation; Heavy soil; Three-dimensional modeling

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