[GRASS-user] help with r.gwflow

[Vishal Mehta]

Thanks Soren,
>From you response, can you please tell me how to do the following two tasks
(which i dont find in the online manual for r.gwflow): the remainder of
your comments i have figured out.

- How can i compute the flux in [m^3/s] for each cell with r.mapcalc?
and

- i have set the bc of the edges and stream cells at constant head for now-
how can i get the budget raster maps you mention?

thanks again,
Vishal

On Sat, Jul 14, 2012 at 12:05 PM, Sören Gebbert <
soerengebbert at googlemail.com> wrote:

> Hi,
> sorry for the delay.
>
> 2012/7/11 Vishal Mehta <vishalm1975 at gmail.com>:
> > Thanks Soren,
> > That explains some of the results i'm getting, with water piling up above
> > the surface in the edges in low-lying areas.
> >
> > Can you please tell me how i can change that to constant flux or constant
> > head? If constant flux, should that be in m/s units?
>
> Constant flux can currently only be defined using sources/sinks with
> unit [m^3/s], that is option q.
> But i can add two new options (fn, fe) that defines the flux in
> northern or eastern direction using the unit [m/s]
> that will be multiplied internally with the northern or eastern face
> area of the cell?
>
> Otherwise you need to compute the flux in [m^3/s] for each cell with
> r.mapcalc.
>
> >
> > My problem though is that i dont know what a constant flux or head at the
> > edges should be set to. For now the only bc i have put in there
> deliberately
> > (beyond the default you mention) is that i have set constant head in
> stream
> > pixels. I'll have to let flow through at the edges but i have no idea
> what
>
> You can use the river boundary condition to specify the flux in stream
> pixel.
>
> > that flow should be. Are there some ways of setting the edge conditions
> such
> > that the gw evolution in the central areas of interest are not highly
> > influenced?
>
> You can set the boundary of interest to constant head pixel and
> compute the flow throw the boundary pixel using the budget option.
> The resulting budget raster map shows the flow from active cell into
> sources, sinks and constant heads in [m^3/s].
>
> Best regards
> Soeren
>



-- 
Vishal K. Mehta, PhD
Scientist
Stockholm Environment Institute - US
133 D St Suite F
Davis CA 95616
www.sei-us.org
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