Ken, I'm confused about what you are trying to do with r.watershed, because the output from the module is:
accumulation=name Name for output accumulation raster map Number of cells that drain through each cell tci=name Name for output topographic index ln(a / tan(b)) map spi=name Stream power index a * tan(b) Name for output raster map drainage=name Name for output drainage direction raster map basin=name Name for output basins raster map stream=name Name for output stream segments raster map half_basin=name Name for output half basins raster map Each half-basin is given a unique value length_slope=name Name for output slope length raster map Slope length and steepness (LS) factor for USLE slope_steepness=name Name for output slope steepness raster map Slope steepness (S) factor for USLE I think you want a hydrologic model, and r.watershed is NOT that. What are you trying to obtain? Tom On Thu, Aug 31, 2017 at 1:47 PM, Ken Mankoff <[email protected]> wrote: > Hi List, > > 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? > > 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. > > 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 > > 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. > > Thanks, > > -k. > > _______________________________________________ > grass-user mailing list > [email protected] > https://lists.osgeo.org/mailman/listinfo/grass-user >
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