evaporation vs. precipitation

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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sapmot
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Joined: Tue Jan 15, 2013 6:47 am
Location: Germany

evaporation vs. precipitation

Post by sapmot » Wed Jan 16, 2013 8:42 am

Hello,

i try to model the constant infiltration of water on a soil column under high evaporation conditions which should later include the reactive transport in the column. So, as a first step i set up a simple HP1 model infiltrating a constant cloride concentration on the column. If i consider now the evaporation, i would expect a higher effluent concentration than the infiltrating solution at the upper boundary.
In on of the other topics i found the following note about the callculation of precipitation concentrations with HYDRUS, what just my understanding of the situation.
Re: salinty simulation

Postby Jirka » Wed Jan 09, 2013 3:28 pm
The flux across the atmospheric BC is the difference of Precipitation/Irrigation and Evaporation. Thus when evaporation is larger than precipitation, then no water (and salts) enter the transport domain. Water (and salts) enters the transport domain only when Precipitation is larger than evaporation. The code does adjust the concentration of infiltrating water to the ratio of precipitation and evaporation as follows:

cPrec=Prec/(Prec-Evap)*cPrec

J.
this seems to work for the general solute transport. But when I set up this problem in a HP1 model, the maximum concentration in the column is just the concentration of the upper boundary solution for the precipitation - without any enrichment by evaporation. So it seems HP1 is just subtracting the evaporation amount from the precipitation amount without increasing the concentrations. Is that rhight or did i missinterpret any important parts. Beside, is there any solution for my problem?
As soon as the evaporation is exceeding the precipitation, the cloride concentrations i the column are increasing obove the initial level or is this just a different calculation method starting when evaporation is dominant?

Kind regards and thanks in advance for any help
sapmot

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