Overflow and Flush

[nwsmith]

Hi,

I'm currently using the overflow and flush processes to model flow from one soil store to another as follows:
:Flush RAVEN_DEFAULT SOIL[1] SOIL[2]
:-->Overflow RAVEN_DEFAULT SOIL[2] SOIL[3]
:Flush RAVEN_DEFAULT SOIL[2] SOIL[4]

SOIL[2] is a temporary soil store with the purpose to evaluate flow up to a maximum value (set as the capacity of SOIL[2]) going to SOIL[4], while any flow in excess of this maximum value goes to SOIL[3]. So if the maximum of SOIL[2] is not exceeded, nothing should be sent to SOIL[3] (no overflow).

I thought the above process lines would work; however, I'm finding that even when the capacity of SOIL[2] is not exceeded (which I see by the amount being flushed from SOIL[2] to SOIL[4] not being equivalent to the maximum capacity of SOIL[2]), that there is still overflow from SOIL[2] to SOIL[3], which doesn't make sense to me. Any thoughts on why this might be occurring?

Thanks,
Nate

[jrcraig]

Are there any other processes manipulating the SOIL[2] or SOIL[3] storages? I suggest identifying the minimum process configuration that leads to this symptom and replying with the :HydrologicProcesses command block.

Also, make sure that you look at this behavior for all soils/HRUs. You can do this with the following command:

Code: Select all

:CustomOutput DAILY AVERAGE Between:SOIL[2].And.SOIL[3] BY_HRU


If you look at the average watershed response (e.g., in the WatershedMassBalance.csv file) and there are some HRUs with smaller (or non-existent) capacities, this would lead to the symptom you see (because a subset of the landscape is reaching capacity).

[nwsmith]

Thanks, looking at the soil flush and overflow for the individual HRUs showed the issue was due to the HRUs at different elevations reaching capacity and overflowing at varying times due to differences in precip/snowmelt so it makes sense that the basin results showing the average had cases where the average capacity wasn't reached yet there was overflow.

One of the issues I'm having with the model I'm building is trying to replicate a model that evaluates forcings and soil moisture at various elevation bands (I've discretized the elevation bands into HRUs) but then combines all subsequent groundwater processes in a single lumped area. So while the overflow now makes sense in my Raven framework, in comparison with the model I'm trying to replicate, there shouldn't be overflow.

I guess the solution if I did want to try and replicate the model exactly would be to evaluate the hydrologic processes in the various HRUs (split up by elevation) up to a point, then do a lateral flush to a dummy HRU with an area equivalent to the entire subcatchment which is then evaluated for the rest of the processes, unless there's a cleaner way to do that?