LeachMod, model for simulating leaching of saline irrigated soil
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LeachMod is designed to simulate the depth of the water table and the soil salinity in irrigated areas with a time step as selected by the user (from 1 day to 1 year). The program uses small time steps in its calculations anyway for a better accuracy.
In case of a leaching experiment with measured soil salinities, LeachMod can automatically optimize the leaching efficiency by minimizing the sum of the squares of the differences between measured and simulated salinities.
The root zone can consist of 1, 2, or 3 layers.
LeachMod allows the introduction of a subsurface drainage system in a transition zone between root zone and aquifer, and subsequently it determines the drain discharge.
When the irrigation/rainfall is scarce and the water table is shallow, LeachMod will calculate the capillary rise and reduce the potential evapotranspiration to an actual evapotranspiration that, although the reduction may diminish by the capillary rise.
LeachMod can also take into account upward seepage from the aquifer or downward flow into it. The latter flow is also called natural subsurface drainage.

This model is somewhat similar to SaltCalc.
On the one hand the water management options are fewer (e.g. re-use of drainage or well water for irrigation do not feature here), but the model is more modern in the sense that the variable input for each time step is given in a table so that the calculations over all the time steps are done in one go. Moreover, by inserting the observed values of soil salinity in the data table, the model optimizes the leaching efficiency of the soil automatically.
          On 11 July 2015 LeachMod was updated to include more rigorous data checks.
On 7 April 2016 the program was updated again and the initial soil salinity can now be be introduced for the various rootzone layers separately instead of one value for the whole rootzone.
          On 3 march 2017, the distribution of the evaporation over the various rootzone layers was refined, leading to a small change in the salt distribution over these layers.

Start: The program starts clicking on LeachMod.Exe. More information is given in the program itself.

Further reading
A description of the principles of water and salt balances in the soil on which LeachMod is based is to be found on this balances page

An article on the use of LeachMod for the reclamation of a saline heavy clay soil (vertisol) by rice cropping was published in the International Journal of Environmental Science, see this website.

Another paper has beed added to this website as the: Khorezm case .

Experiences with LeachMod can be further inspected in this conference paper .



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Experiences: For improvement, I am interested to learn about your experiences with LeachMod. For this there is a contact form.

LeachMod allows for time dependent hydrological conditions and the introduction of a subsurface drainage system. A version called LeachModS has been made conataining a table for input of time dependent salinity of the irrigation water.

An extended version (LeachModE) with surface drainage and an option for rice cropping with input of the infiltration capacity of the soil, can be downloaded with this link The extended version is useful for vertisols (swelling heavy clay soils with rice crops in standing water).

The model DrainApp is similar to LeachModE, but it focusses on the presence of a subsurface drainage system. The DrainApp manual is found at this place.

Further an article on irrigation, drainage and leaching efficiencies and sufficiencies can be consulted as the Drain application publication.

The model LeachSalt is in development. It is an amplification of LeachMod permitting two neighboring areas with different irrigation treatments so that the salt balance in one area may influence the balance of the other. For example it simulates the capillary rise in one area with limited irrigation supply induced by the percolation from the second area with ample irrigation.


                                Example of input:

  input leaching figure

LeachMod simulates the soil salinity on the basis of hydrological data, soil properties, and drainage data. It uses a leaching efficiency to describe the relation between the salt concentration of the soil moisture in the rootzone and that of the percolation water to the underground and aquifer.



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                                Example of output:

output leaching graph    

The root zone can consist up to three soil layers. Underneath is an aquifer, but it is separated from the root zone by a transition layer. When a subsurface drainage system exits, it is located in the transition zone. The soil salinity is calculated for each of these layers.

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                                Example of graphics:

leaching graph output

The soil salinity is presented in graphs by time steps. The salt content of the drainage water can be seen in the output of the hydrological factors, in which the capillary rise in the unsaturated zone is included.