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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@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@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.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.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:
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.
Il giorno mar, 01/08/2023 alle 09.23 -0400, Anna
Petrášová ha scritto:
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-Xwhere 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?
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--
Micha Silver
Ben Gurion Univ.
Sde Boker, Remote Sensing Lab
cell: +972-523-665918
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