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Re: areal recharge term in groundwater equation

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  • poulomizca
    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

      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,

      --- 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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