Hi Tom, You sound like my friend reviewer #2. :)
But seriously, I thank you for thinking critically about what I'm trying to do. However, the inputs I have come from a couples land/ice/snow/atmosphere regional climate model with rain, snowfall, eval, condensations, storage in snow and land, and melting of snow and ice. I think it would be incorrect to take this product and do anything other than route instantaneously and completely at this point. -k. Please excuse brevity. Sent from pocket computer with tiny non-haptic feedback keyboard. > On 31 Aug 2017, at 22:49, Thomas Adams <[email protected]> wrote: > > Ken, > > That would be a gross misapplication of r.watershed and, I'm afraid, is just > bad science; I just don't know how to be more clear on that... > > Tom > >> On Thu, Aug 31, 2017 at 3:52 PM, Ken Mankoff <[email protected]> wrote: >> Hi Tom, >> >> What if we are assuming instantaneous flow and no storage and all of the >> input flow variable leaves the system. Then is r.watershed usable to >> calculate accumulation? >> >> -k. >> >> Please excuse brevity. Sent from pocket computer with tiny non-haptic >> feedback keyboard. >> >>> On 31 Aug 2017, at 21:17, Thomas Adams <[email protected]> wrote: >>> >>> Ken, >>> >>> You wrote: >>> >>> 'If I give r.watershed a precip map as input (flow parameter), doesn't it >>> route that water down the DEM? And if I know the x,y coordinate of a point >>> in a stream, doesn't the accumulation at that point represent all of the >>> up-basin precip that is routed past that point?' >>> >>> ANSWER: NO!!!! r.watershed is NOT a hydrologic model and does NOT take >>> precipitation as an input raster. >>> >>> 'Daily water runoff from the Greenland ice sheet for ~50 years' >>> >>> ANSWER: NO!!!! same as above >>> >>> You want something like r.topmodel or r.sim.water in GRASS, not that I'm >>> necessarily suggesting these would meet your needs. There is also ITZI >>> (https://www.itzi.org/) which may be appropriate since flow over glaciers >>> (if you're focused on glaciers) in Greenland, should be largely impervious. >>> >>> You would need r.watershed and r.water.outlet to aid you in the application >>> of hydrologic models like topmodel, ITZI, and sim.water. But, there are >>> many dozens more hydrologic models, such as VIC, PRMS, etc. >>> >>> Tom >>> >>> >>>> On Thu, Aug 31, 2017 at 3:01 PM, Ken Mankoff <[email protected]> wrote: >>>> Hi Tom, >>>> >>>> > On 31 Aug 2017, at 20:30, Thomas Adams <[email protected]> wrote: >>>> > You "want 14,000 values" of what?? >>>> >>>> One grid cell from each of 14,000 accumulation rasters. >>>> >>>> > 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. >>>> >>>> If I give r.watershed a precip map as input (flow parameter), doesn't it >>>> route that water down the DEM? And if I know the x,y coordinate of a point >>>> in a stream, doesn't the accumulation at that point represent all of the >>>> up-basin precip that is routed past that point? >>>> >>>> > And you say you have "14,000 flow rasters to be used as input" -- what >>>> > exactly are these 'flow rasters'; >>>> >>>> Daily water runoff from the Greenland ice sheet for ~50 years. >>>> >>>> > what is your goal? I may not understand... >>>> >>>> To find the daily stream flow at a point, based on the runoff that feeds >>>> into that point, or any upstream runoff that eventually makes it to that >>>> point. >>>> >>>> Clearly there is a miscommunication issue here. I apologize if I am not >>>> being clear or using incorrect terminology. >>>> >>>> -k. >
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