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

[Anna Petrášová]

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?
>
> --
>
> --
> 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 lun, 31/07/2023 alle 14.34 -0400, Anna Petrášová ha scritto:
>
>
>
> On Sun, Jul 30, 2023 at 6:01 AM bonushenricus <bonushenricus76 at gmail.com>
> wrote:
>
> Hi
> From r.sim.water, how can I calculate the volume of water stored in
> small water storages placed along a relief and connected to ditches?
> In this article https://doi.org/10.1016/j.agwat.2023.108398 these
> Italian researchers with r.sim.water manage did this calculation, but I
> do not understand how. With a calculation at different times on
> discharge at the entrance to the water storage?
> I tried to contact them, but they did not reply.
> Thanks!
>
>
> Hi,
>
> volume would be simple depth times cell size squared for a certain
> selected area. I would compute it for the final step of the simulation, I
> am not sure what is the purpose of summing it for different time steps.
> Perhaps you could clarify a little bit?
>
> Anna
>
>
>
>
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