[GRASS-user] how to calculate volume of water stored in water storage with r.sim.water?

Thu Aug 3 23:26:23 PDT 2023

Thanks Micha
What a mistake with Manning's coefficient! I took off a zero!
For infil: the soil is sandy. The 24.1 mm/h is taken from the soil map
with published regional data. There are two reference sites in the area
of soil delineation: 48% sand and 22% clay: 7.7 mm/h; 52% sand, 14%
clay: 24.1 mm/h. If I can, I will go and measure on the ground. But for
now, maybe 15 might be good.
The result, however, still doesn't convince me.
If I try the simulation on "invaso6", with the same parameters as
"invaso2", it ends after 10 minutes with a result of 30 cm.

Il giorno mer, 02/08/2023 alle 00.45 +0300, Micha Silver ha scritto:
> Hello Enrico:
> 
> Anna knows this subject better than I do, but I noticed a few
> problems with your command, so here are some comments that might help
> to get a better result.
> 
> First, your man_value is way too high. You probably want something
> like 0.03
> Second, you are using the '-t' flag but no `output_step`, If you add
> output_step of a few minutes, then you should get multiple output
> rasters at each time step.
> Third, you have 40 mm/hr rain_rate and 24.1 mm/hr infiltration rate.
> Is that correct? That means that 60% of the rain is infiltrating
> throughout the 30 minute storm. This might happen in very dry and
> sandy soil. Is that your situation?
> 
> Here's what I tried (changing the above 3 parameters):
> 
> r.external ./reservoir_farm_granello/dem_invaso2.tif output=dem_2
> g.region -ap rast=dem_2
> r.slope.aspect elevation=dem_2 dx=dx_2 dy=dy_2
> r.sim.water -t elevation=dem_2 dx=dx_2 dy=dy_2 rain_value=40
> infil_value=15 man_value=0.0368 depth=water_depth_invaso2_40x30mm
> discharge=discharge_invaso2_40x30mm niterations=30 output_step=5
> random_seed=42 nprocs=8 --overwrite
> 
> This resulted in 5 depth (and 5 discharge) rasters. For example:
> 
> r.univar water_depth_invaso2_40x30mm.05 
> 100% 
> total null and non-null cells: 1197120 
> total null cells: 667811 
> 
> Of the non-null cells: 
> ---------------------- 
> n: 529309 
> minimum: 4.25896e-05 
> maximum: 0.313524 
> range: 0.313481 
> mean: 0.00323487 
> mean of absolute values: 0.00323487 
> standard deviation: 0.0125372 
> variance: 0.000157182 
> variation coefficient: 387.565 % 
> sum: 1712.24596255017 
> micha at RMS:bonuschenricus$ r.univar water_depth_invaso2_40x30mm.25 
> 100% 
> total null and non-null cells: 1197120 
> total null cells: 667811 
> 
> Of the non-null cells: 
> ---------------------- 
> n: 529309 
> minimum: 4.25896e-05 
> maximum: 0.406802 
> range: 0.406759 
> mean: 0.00358821 
> mean of absolute values: 0.00358821 
> standard deviation: 0.0176433 
> variance: 0.000311286 
> variation coefficient: 491.702 % 
> sum: 1899.27293131027
> 
> r.univar discharge_invaso2_40x30mm.05 
> 100% 
> total null and non-null cells: 1197120 
> total null cells: 667811 
> 
> Of the non-null cells: 
> ---------------------- 
> n: 529309 
> minimum: 0 
> maximum: 0.595495 
> range: 0.595495 
> mean: 0.000783053 
> mean of absolute values: 0.000783053 
> standard deviation: 0.0121067 
> variance: 0.000146571 
> variation coefficient: 1546.08 % 
> sum: 414.477138618156 
> micha at RMS:bonuschenricus$ r.univar discharge_invaso2_40x30mm.30 
> 100% 
> total null and non-null cells: 1197120 
> total null cells: 667811 
> 
> Of the non-null cells: 
> ---------------------- 
> n: 529309 
> minimum: 0 
> maximum: 0.595495 
> range: 0.595495 
> mean: 0.000857986 
> mean of absolute values: 0.000857986 
> standard deviation: 0.0125651 
> variance: 0.000157882 
> variation coefficient: 1464.49 % 
> sum: 454.13982509354
> 
> 
> Attached is the final depth map (after 30 minutes).  You might try a
> longer run time (higher niternations)
> One other note: Your region resolution is 0.2 meters (from the
> original DEM) so each pixel is 0.04 sq meters.  The sum of values of
> all non-null cells in the final depth map is about 1900 (from the
> r.univar result). So the total discharge should be about 76 m³. Does
> that sound reasonable?
> 
> HTH
> Micha
> 
> On 01/08/2023 21:35, bonushenricus wrote:
>  
> > 
> > Thank you Anna.
> > I will try to attach the two geotiffs in a compressed folder, with
> > the simplest example of a single ditch, for both reservoirs.
> > EPSG:32632.
> > The ditch is not exactly the same for the two reservoirs, they
> > change a little bit in the final part of the mouth of the
> > reservoir, but it is very similar.
> > Sorry I didn't use a sample vector of points, I did it later with
> > temporal.
> >  
> > > r.slope.aspect elevation=dem_invaso2 dx=dx_invaso2 dy=dy_invaso2
> >  
> > > r.sim.water -t elevation=dem_invaso2 dx=dx_invaso2 dy=dy_invaso2
> > > rain_value=40 infil_value=24.1 man_value=0.368
> > > depth=water_depth_invaso2_40x30mm
> > > discharge=discharge_invaso2_40x30mm niterations=30 --overwrite
> >  
> > > r.slope.aspect elevation=dem_invaso6 dx=dx_invaso6 dy=dy_invaso6
> >  
> > > r.sim.water -t elevation=dem_invaso6 dx=dx_invaso6 dy=dy_invaso6
> > > rain_value=40 infil_value=24.1 man_value=0.368
> > > depth=water_depth_invaso6_40x30mm
> > > discharge=discharge_invaso6_40x30mm niterations=30 --overwrite
> > Thank you very much
> > I am sure there is some mistake on my part!
> > 
> > -- 
> > -- 
> > Perito agrario Enrico Gabrielli
> > progetto F.A.R.M. www.farm-agroecologia.it
> > Tessera n. 633 Collegio Periti agrari prov. Di Modena
> > Biblioteca agricoltura: https://www.zotero.org/groups/aplomb/
> > https://www.inaturalist.org/observations/bonushenricus
> > 
> > Il giorno mar, 01/08/2023 alle 13.17 -0400, Anna Petrášová ha
> > scritto:
> >  
> > > 
> > >  
> > > On Tue, Aug 1, 2023 at 10:23 AM bonushenricus
> > > <bonushenricus76 at gmail.com> wrote:
> > >  
> > > > Thank you, Anna.
> > > > r.sim.water finishes the simulation not at the end of the
> > > > rainfall event, in my case at 30 minutes, but at an earlier
> > > > time. In my case, in the smaller reservoir at 16 minutes, in
> > > > the case of the more extensive reservoir at 24 minutes. But the
> > > > water keeps coming even after that. I imagined that the
> > > > calculation ends when it reaches the steady state of the water
> > > > blade.
> > > > But it's not so. Then I don't understand why it ends at 16 or
> > > > 24 minutes. Doesn't the water continue to arrive after that?
> > > > Shouldn't it increase?
> > > > I cannot understand it. In the reservoirs, the discharge is
> > > > very low, as I expect. But if the discharge does not increase
> > > > and the precipitation continues, I expect the water depth to
> > > > rise again.
> > > > And it is not understandable that two reservoirs, one twice the
> > > > volume of the other, contain the same depth of 30 cm at the end
> > > > of the rainfall.
> > > > To understand how this works, I would apply waterproofing to
> > > > the reservoirs. The ksat, or infil_value, is the only variable
> > > > that can explain this: the larger reservoir loses more water.
> > > > If both reservoirs were waterproof, I would have removed this
> > > > variable. Unfortunately r.sim.water infil=raster where I have
> > > > marked value 0 in the reservoirs does not work. There is
> > > > perhaps a bug that I have reported. So I haven't had a chance
> > > > to test this.
> > > > I don't know how to do it; I can't trust the 30 cm as a value
> > > > to calculate the water volume in the two reservoirs. I will
> > > > have to use another model.
> > > > I will try to use a distributed model. Since I have the data in
> > > > GRASS, I will try using the old geomhydas, hoping the modules
> > > > will work in GRASS8, and then use the Mhydas models in
> > > > OpenFluid. I have no other chance unless someone can help me
> > > > find a solution.
> > > >  
> > > 
> > > 
> > > Unfortunately I haven't had time to look at the reported issue.
> > > Perhaps you could share your data and provide exact commands and
> > > pictures, explaining very clearly what's wrong. 
> > >  
> > >  
> > > > -- 
> > > > -- 
> > > > Perito agrario Enrico Gabrielli
> > > > progetto F.A.R.M. www.farm-agroecologia.it
> > > > Tessera n. 633 Collegio Periti agrari prov. Di Modena
> > > > Biblioteca agricoltura: https://www.zotero.org/groups/aplomb/
> > > > https://www.inaturalist.org/observations/bonushenricus
> > > > 
> > > > Il giorno mar, 01/08/2023 alle 09.23 -0400, Anna Petrášová ha
> > > > scritto:
> > > >  
> > > > > 
> > > > >  
> > > > > On Mon, Jul 31, 2023 at 11:42 PM bonushenricus
> > > > > <bonushenricus76 at gmail.com> wrote:
> > > > >  
> > > > > > Hi Anna
> > > > > > I too immediately thought it was enough to compute it for
> > > > > > the final step of the simulation,
> > > > > > but I noticed that the same slope, same ditches, same
> > > > > > rainfall, for two reservoirs at the same location, same
> > > > > > length along a contour, but different width and depth, at
> > > > > > the final step of the simulation the water depth was always
> > > > > > 30 cm, I went to read the article 
> > > > > > Mitasova, Helena, Chris Thaxton, Jaroslav Hofierka, Richard
> > > > > > McLaughlin, Amber Moore, e Lubos Mitas. «Path Sampling
> > > > > > Method for Modeling Overland Water Flow, Sediment
> > > > > > Transport, and Short Term Terrain Evolution in Open Source
> > > > > > GIS». In Developments in Water Science, 55:1479–90.
> > > > > > Elsevier, 2004.
> > > > > > https://doi.org/10.1016/S0167-5648(04)80159-X
> > > > > > where I read the Saint-Venant equation. I am an
> > > > > > agricultural technician and geographer unfortunately
> > > > > > ignorant of hydrological calculations and serious
> > > > > > mathematics, and I understood, looking at the equation,
> > > > > > that the water depth is the depth of overland flow =
> > > > > > rainfall exces - water flow.
> > > > > > So the final 30 cm should not be understood as accumulated
> > > > > > water, but as the blade of water that was added at that
> > > > > > precise moment.
> > > > > > Isn't my interpretation right?
> > > > > > 
> > > > > 
> > > > > 
> > > > > No, it should be actual water depth.  I didn't understand the
> > > > > discrepancy you are describing?
> > > > >  
> > > > > > 
> > > > > > -- 
> > 
> > 
> > _______________________________________________
> > grass-user mailing list
> > grass-user at lists.osgeo.org
> > https://lists.osgeo.org/mailman/listinfo/grass-user
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