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ESCOMP / CTSM

Community Terrestrial Systems Model (includes the Community Land Model of CESM)
http://www.cesm.ucar.edu/models/cesm2.0/land/
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Generalize groundwater irrigation availability to handle multiple patches per column #593

Closed billsacks closed 5 years ago

billsacks commented 5 years ago

Groundwater irrigation (introduced by @swensosc in ctsm1.0.dev020) will compute the wrong water availability if there are multiple irrigated patches in a single column. Currently this is never the case, but the code should be flexible enough to handle this case.

The problem is in this block of code:

https://github.com/ESCOMP/ctsm/blob/7755baf3f729ff9adb0e39088c02113bbc9ebb58/src/biogeophys/IrrigationMod.F90#L917-L923

Note that this compares patch-level demand / fluxes with column-level availability. I think this can lead to the irrigation flux being overly constrained (e.g., if there are two patches on a column, with one being irrigated and the other not: I think the irrigated patch is currently constrained as if it took up the entire column).

Off-hand, I'm not sure how to solve this problem, but I don't think we want code like this that implicitly assumes one patch per column.

billsacks commented 5 years ago

@swensosc I'm tentatively assigning this to you to at least think about. I'm happy to talk with you more about it.

billsacks commented 5 years ago

Upon further thought, the current behavior is probably okay (I think it leads to irrigation withdrawals being potentially overconstrained, but not undersconstrained as far as I can see), and making this better than it currently is could be tricky. So I'm closing this as a wontfix.

billsacks commented 5 years ago

It turns out that the resolution of this issue falls out naturally in the course of resolving #521 . So I'm reopening this and assigning it to myself.