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<p>(keeping on the maillist)</p>
<p><br>
</p>
<div class="moz-cite-prefix">On 18/04/2019 19:03, Mehrdad Varedi
wrote:<br>
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<div dir="ltr">Hi Micha,
<div>I really appreciate your feedback and thanks for your
explanation. </div>
<div><br>
</div>
<div>What I am interested to do is finding where the water is
accumulated after a rainfall or snowmelt under the ground. It
doesn't need to form a river and any path of accumulation
under the ground is what I am searching for.</div>
<div>I was thinking probably the Flow accumulation or TWI
somehow might be a way to find such locations.</div>
</div>
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<blockquote type="cite"
cite="mid:CA+F3BSBeobWUP4V9UAOcNWtjPROskOorUj68DEjoB9qwnBDBxg@mail.gmail.com">
<div dir="ltr">
<div><br>
</div>
<div>Now, do you think that r.watershed is the best way to go
or any other solution comes to your mind?</div>
</div>
</blockquote>
<p><br>
</p>
<p>In my opinion those are the wrong tools for groundwater flow. But
you might have a look at the r.gwflow module.</p>
<p>And there are many other software applications designed
explicitly for ground water flow: Hydrus or Kineros come to mind.</p>
<p><br>
</p>
<blockquote type="cite"
cite="mid:CA+F3BSBeobWUP4V9UAOcNWtjPROskOorUj68DEjoB9qwnBDBxg@mail.gmail.com">
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<div><br>
</div>
<div>Thank you and kind regards,</div>
<div><br>
</div>
<div>Mehrdad</div>
</div>
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<div dir="ltr" class="gmail_attr">On Thu, Apr 18, 2019 at 4:22
AM Micha Silver <<a href="mailto:tsvibar@gmail.com"
moz-do-not-send="true">tsvibar@gmail.com</a>> wrote:<br>
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<div class="gmail-m_1294959685203069523moz-cite-prefix">On
17/04/2019 19:34, Mehrdad Varedi wrote:<br>
</div>
<blockquote type="cite">
<div dir="ltr">Hi Everyone,
<div>I would like to know how the flow path, flow
accumulation, or topographic wetness is calculated in
cities versus farms.</div>
<div>In other words how to take into account the effect
of non-penetrable areas in forming the above-mentioned
layers based on a DEM and penetrability score for the
study area?<br clear="all">
<div><br>
</div>
</div>
</div>
</blockquote>
<p>No answers yet, so I will give a try:</p>
<p>Each of the variables in your question are geomorphology
characteristics. They depend only on elevation, slope,
aspect. Flow accumulation is an area, TWI is area divided
by tan(slope), etc. These characteristics have nothing to
do with infiltration (i.e. penetrable areas). </p>
<p><br>
</p>
<p>Having said that, the GRASS module r.watershed can take
two input rasters: flow and retention, which change the
output flow accumulation. If you have spatial data on soil
retention properties, or disturbances to surface flow, you
can apply them to r.watershed to get a more "realistic"
accumulation grid. The defaults are 100 for retention (no
infiltration, all water flowing into a cell also goes out)
and 1.0 for flow (no disturbances, and no additional
contribution for each cell)</p>
<p><br>
</p>
<p><br>
</p>
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<div dir="ltr">
<div>
<div>Thanks for your help,</div>
<div><br>
</div>
<div dir="ltr"
class="gmail-m_1294959685203069523gmail_signature">Mehrdad</div>
</div>
</div>
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</blockquote>
<pre class="gmail-m_1294959685203069523moz-signature" cols="72">--
Micha Silver
Ben Gurion Univ.
Sde Boker, Remote Sensing Lab
+972-523-665918</pre>
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</blockquote>
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<br clear="all">
<div><br>
</div>
-- <br>
<div dir="ltr" class="gmail_signature">Mehrdad Varedi</div>
</blockquote>
<pre class="moz-signature" cols="72">--
Micha Silver
Ben Gurion Univ.
Sde Boker, Remote Sensing Lab
cell: +972-523-665918</pre>
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