Swale infiltratrion tests using Hydrus 1D

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Joined: Tue Dec 19, 2023 3:10 am
Location: Kazakhstan

Swale infiltratrion tests using Hydrus 1D

Post by shohon » Tue Dec 19, 2023 8:12 am

Hello everyone!

I would highly appreciate if anyone could help me with the following situation. At the moment I'm trying to simulate using Hydrus 1D (free version) field infiltration tests in the swale. The experiments were conducted using pumped water from the nearby well. The swale consists of several layers for improving its infiltration capacity (at the top is local soil, then sand and followed by gravel layer). Below the gravel layer is the local soil layer (which most probably has much lower hydraulic conductivity than gravel layer). There are three soil moisture sensors located vertically (at different depths) right below the middle of the swale, data from which I would like to use for calibration of the model (I'm assigning them as observation nodes). The setup is 136 cm deep, which I had divided into 1000 nodes, as in the beginning the model couldn't run with a lower resolution.
Upper BC - Atmospheric BC with Surface layer (I'm converting the volume of pumped water per minute to mm of water per minute)
Lower BC - Free drainage (GW table is not close (deeper than 3 meters) to the bottom of the setup)
I'm using a water content as the initial conditions. And I'm using the default model for calculations.
I'm a new user, so I had quite some problems for setting up the initial model in terms of convergence.
So my questions are:
1) Is it possible at all to simulate my experimental setup in Hydrus 1D? Or is Hydrus 2D more preferred?
2) From the forum I found a recommendation that it is better to assign sand hydraulic parameters to gravel and to increase Ks later. I followed this recommendation, but I'm facing a problem of not convergence (Numerical solution has been stopped since it has not converged in 10 consecutive time steps !), when I increase the Ks of the gravel layer. Is there any suggestion to resolve this issue? Can anyone recommend some initial values for gravel hydraulic parameters?
3) As I mentioned I have the soil moisture data from the sensors. Depending on the infiltration test and the depth of flooding in the swale, soil moisture rises to different values. But when I simulate in Hydrus, in all cases the soil moisture rises to the set value in soil hydraulic parameters. Is there any recommendation about how I can tune the model so that the soil moisture will not reach saturation in all infiltration cases and vary depending on other factors?

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