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• ## Re: areal recharge term in groundwater equation

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• Hi, In my case, I m entering value of aereal recharge node basis; so when multiplied by elemental area; do i need to multiply by (area/3) or simply area of
Message 1 of 4 , Jul 3, 2009
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Hi,

In my case, I'm entering value of aereal recharge node basis; so when multiplied by elemental area; do i need to multiply by (area/3) or simply area of that element as I'm putting my value node basis.
Kindly respond at the earliest.

with best regards,
Poulomi

--- In gwmodel@yahoogroups.com, "Schreiber, Robert" <SchreiberRP@...> wrote:
>
> Dear Poulomi:
>
> Perhaps I can help you.
>
> At CDM, our DYNSYSTEM groundwater flow simulation code, DYNFLOW (see
> www.dynsystem.com ), uses triangular finite elements with linear
> interpolation for solving the governing differential equation. The
> modeler specifies areal recharge on an element basis, with measurement
> units of length per time [L/T]. The code multiplies the specified
> element areal recharge by the area of the element, thereby producing an
> element recharge flux with measurement units of length-cubed per time
> [L^3/T]. The code then distributes a designated portion of this element
> recharge flux to each of the 3 nodes that comprise the element, as a
> nodal point recharge flux. The distribution rule can be simply one-third
> to each node, or it can be done based on a Thiessen polygon type
> allocation (which would be appropriate for all but equilateral triangle
> shaped elements).
>
> Now, to answer your question about the sign of the areal recharge: If
> the recharge represents flux being added to the groundwater flow system,
> then it should be assigned a positive sign - and vice versa. Thus,
> infiltration due to precipitation would be assigned a positive sign, but
> a net loss due to evapotranspiration would be assigned a negative sign.
>
> I hope this helps you.
>
> Robert P. Schreiber, P.E., BCEE, D.WRE
>
> VP & Groundwater Subdiscipline Leader
>
>
> CDM
> One Cambridge Place
> 50 Hampshire Street
> Cambridge, MA 02139 USA
>
> email:schreiberrp@...
> Phone and Fax: (617) 452-6251
> Cell: (617) 512-6819
> Alternate email: schreiberrp@...
>
>
> From: gwmodel@yahoogroups.com [mailto:gwmodel@yahoogroups.com] On Behalf
> Of poulomi ganguli
> Sent: Saturday, June 27, 2009 12:56 AM
> To: gwmodel@yahoogroups.com
> Subject: [gwmodel] areal recharge term in groundwater equation
>
> Hi all,
>
> I am using finite element modeling for calculation of groundwater head
> in an aquifer area. I'm taking recharge term at the right hand side of
> the equation. but i am in a confusion whether areal recharge term (i.e.,
> recharge from rainfall, irrigation returnflow) is taken to be positive
> or negative if we use this term at RHS. In case of point source/sink,
> (i.e., well discharge/recharge term) we are taking -ve for well
> discharge and +ve for recharging well. What should be taken in case of
> areal recharge term is bit confusing. If anybody pls clear these doubts,
> will be a great help for me.
>
> with best regards,
> Poulomi
>
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