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

[bonushenricus]

Sorry
I was too impetuous.
I have to think about it more calmly.
In fact, I am too ignorant on the subject.
If it were the water blade, it wouldn't make sense for it to grow
faster in case of the smaller reservoir.
But I would expect, in my logic, that the water depth would again grow
in the smaller reservoir.
I will do more tests, try to understand. Or maybe the model is not
adapted to the presence of small ponds. Consider that these are 30 and
70 m³ ponds, very small indeed.
-- 
-- 
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 16.23 +0200, bonushenricus 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.
> -- 
> -- 
> 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?
> > > 
> > > -- 
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