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Unadjusted Parameters in PEST with Pilot Points


Chris Greer
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I am running a transient PEST model with pilot points, using HK and RCH values. However, during the run I notice that the RCH values are not changing between optimization iterations. None of the points are defined as fixed.

I created the RCH scatter points by duplicating the HK scatter points then editing the values. Could the additional "Active" field (populated with "1"'s) in the new RCH scatter point file be causing the problem?

Both pilot-point-defined Parameters are referencing the correct scatter point sets.

I am using 18 pilot points, but have over 100 Observation Points so I do not think I am violating that ratio.

Thanks for your help!

Chris

post-12658-0-34854900-1355504908_thumb.j

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Thanks for the responses! I will have to come back to this issue to polish off the calibration, but I need to move forward with my "predictive" modeling to generate a preliminary drawdown map.

How do I get the PEST-derived pilot point HK's back into MODFLOW to run a transient forward model from this point? I've imported the optimal values from the Parameter dialogue, and can contour the PEST-derived HK's, but I still don't see those new K's in the HK array under LPF in the 3D Grid Data section. I didn't see how to do this in the tutorials.

Thanks, Chris

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  • 2 weeks later...
  • 6 months later...

I successfully imported the optimal values - thanks! But I am still trying to interpret the sensitivity results from my PEST run. I've attached a plot of the sensitivity results (the RCH sensitivities aren't zero, but are much less than the values for K). I've also attaché the .sen file. Are these raw sensitivities or relative sensitivities? I've tried reading through the sensitivity section of the PEST manual (5.3.2) but I'm till having trouble figuring out exactly what numbers I have here.post-12658-0-88303300-1374508725_thumb.jriversideeast_1l_transonly_1211_pilotpts_sen.txt

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This is from an old email from John Doherty. They are "raw" sensitivities.

The latest version of PEST does not write out relative sensitivities. I think they were a bit misleading.

So the sensitivities that are printed out are sensitivities as PEST sees them. If a parameter is log transformed they are with respect to the log of the parameter. If not, they are with respect to the parameter itself. This, I think, is the best way to know whether something should be done to the parameter - whether it should in fact be log transformed (as this is the great equalizer of sensitivities and log transformation can reduce the sensitivity of an over-bearing parameter) or maybe held fixed (if the sensitivity is just too small).

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