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    The r.water.outlet module takes as input a flow direction raster
    that needs to be created first by r.watershed. So the SFD/MFD
    question is irrelevant at this stage. When you first ran r.watershed
    you chose which method to use for determining flow direction for
    each pixel. Further, SFD/MFD influences only the stream routing, not
    the total number of cells in the basin. I'm pretty sure that if you
    run r.watershed once with MFD and again with SFD, you'll get the
    same basin, only with slightly different stream networks. <br>
    AFAIK there should never be a situation where water is directed out
    of the basin. So all cells that flow into cell C are then directed
    downstream to your final drainage point.<br>
    <br>
    <div class="moz-cite-prefix">On 08/31/2017 10:04 PM, Ken Mankoff
      wrote:<br>
    </div>
    <blockquote type="cite"
      cite="mid:81312416-5630-44ED-9B5B-EBC2CCF0FE42@gmail.com">
      <meta http-equiv="content-type" content="text/html; charset=utf-8">
      <div>Yes. This! What you wrote. </div>
      <div><br>
      </div>
      <div>But the issue is that r.water.outlet make basins based on
        SFD, right? What if there are 10,000 cells that feed into cell C
        at x,y, and then cell C feeds 49% (based on MFD) into the basin.
        These 10,000 cells are not included in the r.water.outlet basin,
        are they?<br>
        <br>
          -k. 
        <div><br>
        </div>
        <div>Please excuse brevity. Sent from pocket computer with tiny
          non-haptic feedback keyboard. </div>
      </div>
      <div><br>
        On 31 Aug 2017, at 20:51, Micha Silver <<a
          href="mailto:tsvibar@gmail.com" moz-do-not-send="true">tsvibar@gmail.com</a>>
        wrote:<br>
        <br>
      </div>
      <blockquote type="cite">
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          I'm also not clear what you are asking. But risking a guess:<br>
          You could run r.water.outlet *1 time* to get the basin. Then
          use that raster as a MASK, so that the next process will
          address only the pixels within the basin. Now do a loop with
          r.univar on all 14,000 flow rasters, and you'll get 14,000
          results with total, min, max, mean, etc of the basin pixels
          for each of the flow rasters.<br>
          <br>
          --<br>
          Micha<br>
          <br>
          <div class="moz-cite-prefix">On 08/31/2017 09:30 PM, Thomas
            Adams wrote:<br>
          </div>
          <blockquote type="cite"
cite="mid:CAGxgkWhJ8PWAh+Av1u5KUcLHvqa5NZZvqx+SQzJ0eVz2h3e-0A@mail.gmail.com">
            <div dir="ltr">
              <div>
                <div>Ken,<br>
                  <br>
                </div>
                You "want 14,000 values" of what?? Your original email
                stated you were "trying to determine flow past a
                drainage basin outlet" -- r.watershed does NOT do this,
                if indeed this is what you want. And you say you have
                "14,000 flow rasters to be used as input" -- what
                exactly are these 'flow rasters'; what is your goal? I
                may not understand...<br>
                <br>
              </div>
              Tom<br>
              <div class="gmail_extra"><br>
                <div class="gmail_quote">On Thu, Aug 31, 2017 at 2:24
                  PM, Ken Mankoff <span dir="ltr"><<a
                      href="mailto:mankoff@gmail.com" target="_blank"
                      moz-do-not-send="true">mankoff@gmail.com</a>></span>
                  wrote:<br>
                  <blockquote class="gmail_quote" style="margin:0px 0px
                    0px 0.8ex;border-left:1px solid
                    rgb(204,204,204);padding-left:1ex">
                    <div dir="auto">
                      <div>Hi Tom,</div>
                      <div><br>
                      </div>
                      <div>I have 1 DEM and 14,000 flow rasters to be
                        used as input. I want 14,000 values, one at a
                        specific coordinate from each acc output. </div>
                      <div><br>
                      </div>
                      <div>I can do this by running r.watershed 14,000
                        times. That is slow, unless I'm missing
                        something (e.g. It works with I.group variables
                        or Time Series data more efficiently). </div>
                      <div><br>
                      </div>
                      <div>An alternative approach is possible if I knew
                        the complete drainage basin *and* the fractional
                        value of each cell that contributed to the
                        basin. In this case I don't need to route. But
                        basins from r.watershed or r.water.outlet, I
                        think, use SFD not MFD (no cell is ever in 2
                        basins, are they?), and I don't know how to get
                        the fractional contribution from each cell. </div>
                      <div><br>
                          -k. 
                        <div><br>
                        </div>
                        <div>Please excuse brevity. Sent from pocket
                          computer with tiny non-haptic feedback
                          keyboard. </div>
                      </div>
                      <div>
                        <div class="gmail-h5">
                          <div><br>
                            On 31 Aug 2017, at 19:59, Thomas Adams <<a
                              href="mailto:tea3rd@gmail.com"
                              target="_blank" moz-do-not-send="true">tea3rd@gmail.com</a>>
                            wrote:<br>
                            <br>
                          </div>
                          <blockquote type="cite">
                            <div>
                              <div dir="ltr">
                                <div>
                                  <div>
                                    <div>Ken,<br>
                                      <br>
                                    </div>
                                    I'm confused about what you are
                                    trying to do with r.watershed,
                                    because the output from the module
                                    is:<br>
                                    <br>
                                    accumulation=name <br>
                                    Name for output accumulation raster
                                    map <br>
                                    Number of cells that drain through
                                    each cell <br>
                                    tci=name <br>
                                    Name for output topographic index
                                    ln(a / tan(b)) map <br>
                                    spi=name <br>
                                    Stream power index a * tan(b) <br>
                                    Name for output raster map <br>
                                    drainage=name <br>
                                    Name for output drainage direction
                                    raster map <br>
                                    basin=name <br>
                                    Name for output basins raster map <br>
                                    stream=name <br>
                                    Name for output stream segments
                                    raster map <br>
                                    half_basin=name <br>
                                    Name for output half basins raster
                                    map <br>
                                    Each half-basin is given a unique
                                    value <br>
                                    length_slope=name <br>
                                    Name for output slope length raster
                                    map <br>
                                    Slope length and steepness (LS)
                                    factor for USLE <br>
                                    slope_steepness=name <br>
                                    Name for output slope steepness
                                    raster map <br>
                                    Slope steepness (S) factor for USLE
                                    <br>
                                    <br>
                                  </div>
                                  I think you want a hydrologic model,
                                  and r.watershed is NOT that. What are
                                  you trying to obtain?<br>
                                  <br>
                                </div>
                                Tom<br>
                                <div>
                                  <div><br>
                                    <br>
                                    <br>
                                  </div>
                                </div>
                                <div class="gmail_extra"><br>
                                  <div class="gmail_quote">On Thu, Aug
                                    31, 2017 at 1:47 PM, Ken Mankoff <span
                                      dir="ltr"><<a
                                        href="mailto:mankoff@gmail.com"
                                        target="_blank"
                                        moz-do-not-send="true">mankoff@gmail.com</a>></span>
                                    wrote:<br>
                                    <blockquote class="gmail_quote"
                                      style="margin:0px 0px 0px
                                      0.8ex;border-left:1px solid
                                      rgb(204,204,204);padding-left:1ex">
                                      <div dir="ltr">Hi List,
                                        <div><br>
                                        </div>
                                        <div>I'm trying to determine
                                          flow past a drainage basin
                                          outlet. The complicating
                                          factor is that I need to do
                                          this each day for 40 years. If
                                          I do "r.watershed" ~14,000
                                          times I'll get the results,
                                          but it will take 3 days. It
                                          seems that r.watershed is
                                          likely calculating many things
                                          each time through the loop. Is
                                          there a more efficient way to
                                          this? A flag to r.watershed
                                          that isn't documented?
                                          Something with time-series?</div>
                                        <div><br>
                                        </div>
                                        <div>Alternatively, because I
                                          only need the flow at the
                                          outlet, I could calculate the
                                          basin, not route the flow, and
                                          instead sum the values in the
                                          basin. I assume this would
                                          take seconds or minutes rather
                                          than days. In this case I'm
                                          not sure of the best way to
                                          define the basin. I tried
                                          doing r.water.outlet upstream
                                          from the outlet, but I think
                                          this uses SFD, which means the
                                          basin may be significantly
                                          underestimated.</div>
                                        <div><br>
                                        </div>
                                        <div>I also tried
                                          inverting/flipping the DEM and
                                          then running r.watershed with
                                          convergence=1, and a flow
                                          equal to 0 everywhere except
                                          1000 at the outlet (now the
                                          source due to the inversion)
                                          to see where it flooded
                                          upstream (now downstream due
                                          to the inversion). This didn't
                                          seem to work... because basins
                                          are filled and flow routes to
                                          the edge of the DEM, I could
                                          not pick out the </div>
                                        <div><br>
                                        </div>
                                        <div>Any advice how to either a)
                                          efficiently route 14,000 FLOW
                                          rasters over 1 DEM or b)
                                          determine the full basin will
                                          be much appreciated.</div>
                                        <div><br>
                                        </div>
                                        <div>Thanks,</div>
                                        <div><br>
                                        </div>
                                        <div>    -k.</div>
                                      </div>
                                      <br>
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            <pre wrap="">_______________________________________________
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          </blockquote>
          <br>
          <pre class="moz-signature" cols="72">-- 
Micha Silver
Ben Gurion Univ.
Sde Boker, Remote Sensing Lab
cell: +972-523-665918</pre>
        </div>
      </blockquote>
    </blockquote>
    <br>
    <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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