The case of shallow water table

The HP1 code incorporates modules simulating
(1) transient water flow in variably-saturated media,
(2) transport of multiple components, and
(3) mixed equilibrium/kinetic geochemical reactions.
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tsutchi
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The case of shallow water table

Post by tsutchi » Tue Jan 19, 2010 1:36 am

<font face="Arial"></font id="Arial">Numerical simulations using HYDRUS-1D for no-ponding boundary conditions do not converge when the soil column has a water table less than air-entry pressure. Is there any way to simulate water content and pressure distribution profiles in a soil column with shallow water table?
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Mohamed Khaled

Jirka
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Post by Jirka » Tue Jan 19, 2010 3:38 am

What does that mean "the soil column has a water table less than air-entry pressure"?

J.

tsutchi
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Joined: Fri Mar 07, 2008 12:18 pm
Location: Japan

Post by tsutchi » Wed Jan 20, 2010 2:25 am

For example, if you have a soil with an air entry of 40 cm (infered from the water retention curve), you pack this soil in a 100 cm column. If the water table is set at depth less than 40 cm from soil surface the zone above it is nearsaturated because of the capillary fringe effect. In this case numerical simulations do not converge. For instance Shah and Ross (2009) quoted this problem.
Shah N. and Ross M. 2009. Variability in Specific Yield under Shallow Water Table Conditions. Journal of Hydrologic Engineering,Vol. 14, No. 12: 1290–1298. <blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by Jirka</i>

What does that mean "the soil column has a water table less than air-entry pressure"?

J.
<hr height="1" noshade id="quote"></font id="quote"></blockquote id="quote">

Jirka
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Joined: Sat Mar 16, 2002 3:47 pm
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Location: Riverside, CA

Post by Jirka » Wed Jan 20, 2010 5:19 am

Are you using BC soil hydraulic model or modified VG model. Only these two models recognize air-entry value. VG model does not and thus should work fine. If you use the other two models and thus do have a fully saturated column, then obviously your boundary conditions must be such so that the system can handle that. You cannot apply flux to a fully saturated column.

J.

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