Stock limit observance

[ekorning]

Hi,
I am building a STSM-SF for sagebrush rangeland systems. I’m using the stock/flow submodeling capabilities in a novel way (aka not what it was designed for) to simulate and track the fractional vegetation components (stocks) that make up each cell’s vegetation state based on annual canopy cover growth and post-fire recovery rates (flows). I set stock min/max limits to be 0 and 100, respectively, but have a number of cells within stocks exceeding ceiling limits during simulation runs. The flow “growth” rates are executing as expected/designed, which will push some stocks to the ceiling limits within a cell; I anticipated they would “cap” at those limits, but it appears they keep going. I’m trying to track down if I have missed a setting somewhere or misunderstood terminology for how this feature executes in the SF portion of the model. Stock amount “per unit area” refers to the cell, correct? Any thoughts or suggestions for resolving so the limits are observed would be greatly appreciated; I’m working with Syncrosim (v2.2.27); stsim (v3.2.28); stsimsf (v.3.3.2).

Thanks!

Beth

[leonardo-frid]

Hi Beth,

Thanks for sharing this observation. My initial response is that you may have discovered a bug in the stock limit feature in the software. Would you be able to share your library with us so we can understand your use case better? If the file is not too large, you could sent it to info@apexrms.com. Otherwise, you could post it somewhere for us to download.

Thanks,
Leonardo

[leonardo-frid]

Thanks Beth for pointing out this issue and sharing your library. After reviewing your library we were able to determine that the use case that leads to this problem is a “Flow Pathway” where the “Target Type” is “From Stock” and your limit is on the “From Stock” for that pathway. In this case “Stock Limits” on the “From Stock” do not get observed. We will work on fixing this issue. In the meantime for users experiencing the same problem the workaround is to reverse the “Flow Pathway” From/To Stocks and set the “Target Type” as “To Stock”.

[leonardo-frid]

Just a quick follow-up that there actually was a bug in stsim sf whereby the limits are not properly checked when the cell size is not equal to 1 area unit. Absolute stock amounts on a cell were being compared to limits on stock density per unit area. A fix will be ready shortly in the package stsimsf v3.3.5.

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