Syncrosim › Forums › ST-Sim & State-and-Transition Simulation Models › Extracting ST-Sim Stock Flow sampled flow rates using rsyncrosim
Tagged: flow rate, output, state attribute, stochastic
- This topic has 1 reply, 1 voice, and was last updated 1 month, 2 weeks ago by Leonardo Frid.
April 18, 2023 at 6:24 pm #21879Leonardo FridKeymaster
Question from an ST-Sim user:
I’m working on an updated version of the LUCAS-W model I’ve talked with you about earlier. This is a land-use change model where water use is associated with each LULC cell. The data needs to be reprocessed in rsyncrosim to assess total water use per agency management area at the end of each timestep, which subsequently alters land-use change rules in the next timestep in that agency’s management area. I am wondering if there is a way to pull the actual rates sampled from a stochastic distribution in each timestep into RSyncroSim.
The previous version modeled this simply by importing the State Attribute Output into rsyncrosim and summing across the management area strata.
Total Water Use = Sum(Per-Cell Water Use State Attribute)
Where the State Attribute determines the flow between water stocks (water use extracts water from the stock). One of the things about the new version we’re working on is that the associated water use is variable across years, based on actual empirical distributions. This is being modeled via Flow Multipliers, which have a variety of different distributions (Normal, Gamma, and Uniform), that alter a set of “base” water use rates. (These are currently set up as “Always” sampled, could also be “Timestep, Iteration” if need be). The way I have it set up is:
Total Water Use = Sum(Per-Cell Water Use State Attribute) * Expected Flow Modifier
Where the Expected value is the Mean for the Normal / Gamma distributions, and calculated as Mean(DistributionMin, DistributionMax) for the Uniform distribution. The long-term average water use should be the same, but I am wondering if there is a way to pull in the actual sampled rates instead?
Alternatively, is State Attribute * Flow Modifier = “stsimsf_OutputFlow” datasheet? Would it make more sense to just use that directly, rather than recalculating the water-useApril 18, 2023 at 6:27 pm #21880Leonardo FridKeymaster
If I understand your question correctly, your flow multipliers are now stochastic and are sampled from a distribution in SyncroSim. You would like to know the sampled rate values and pull them into your rsyncrosim external program. As I understand it, these values vary across years so your sampling frequency should be “Iteration and Timestep”.
stsimsf_OutputFlow will get you the total flow “Amount” broken down by source state class, strata, etc… Using this datasheet, you would then need to back calculate the rate taking into account total area. For example if a particular row has a value of x that represents a flow amount for that combination of strata, your rate would be x divided by the total area on the landscape associated with that combination of strata.
Note that you could also get the rate associated with each individual cell on your landscape by getting the raster you need from stsimsf_OutputSpatialFlowGroup. These values are already rates specified as flow amount per unit area.
One final note: if you prefer to continue using State Attributes to specify your rates, this datasheet also allows for specifying distributions rather than single values.
Hope that helps!
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