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Bruce Campbell

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  1. Hi -- I'm getting different water-level results with GMS 10.4.7 files when I switch from a PEST calibrated binary version to native text files. Here's the workflow: 1) Build and calibrate the models using PEST in GMS, 2) Get good results and acceptable calibration, using pilot points for aquifer horizontal hydraulic conductivities (HK) and specific yield (Sy) (for the surficial aquifer), 3) Interpolate the calibrated pilot point HK and Sy data to a 2-D grid created from the 3-D grid (same cell size and alignment) with the same interpolation methods as PEST used, 4) Repla
  2. Does the 10.4.3 version of GMS produce text files that incorporate PEST variables/parameters without having to do it manually?
  3. Hi -- I'm having trouble getting all of the water level residuals out of a multi-layer transient MODFLOW model in GMS 10.3.8. I need to get the residuals out layer-by-layer. For instance, in the surficial layer of the model, I have 224 observation points but the number of water levels associated with each point varies. There may be only 1 water level with a observation point or there may be 100's of water levels with another observation point over a period of time simulated by the model. When I go through the Plot Wizard, I can get one residual per observation point but can't see a way to get
  4. Hi Sylvain -- I've had good results using a 2-D grid. I) create a 2-D grid from the 3-D grid 2) do a linear (or other type) interpolation of your raster recharge data to the to 2-D grid. These will stack up for your 120 rasters under the 2-D grid 3) Go to MODFLOW -> Optional Packages -> Recharge and the use the 2D Dataset - > Array to put the 120 datasets into the model at the appropriate stress period
  5. Hi Michal -- I do all of my pest work outside of GMS. I set up the pilot points and other variables in GMS, save and run the files - up to the point where the *.PST file is written. I stop the execution in GMS and do all of the PEST work in DOS prompt windows. The *.PST file usually requires extensive edits but when I get in all back together, PEST works fine.
  6. Hi -- Wanted to see if an attribute could be added to the water-level observation coverage indicating a PEST observation group. Of course. this would have to travel through the PEST setup process and end up in the *.PST file, somehow. In conversations with John Doherty, he recommends putting the water-level observations into groups - by aquifer / model layer / other, to help with the PEST process. I've tried to think of way to edit the *.PST file but haven't been successful.
  7. Hi Michal -- I've had this same problem. What I've done is interpolate the pilot point values to a 2-D grid (hopefully, the same as the model 3-D grid) and then import the interpolated values into the corresponding model layer input. For example, horizontal hydraulic conductivity pilot points for the models surficial layer are interpolated to the 2-D grid then in your MODFLOW package, use the "2D Dataset -> Layer" command to place the interpolated horizontal hydraulic conductivity values into layer 1 of the model. Do this for all of your pilot point sets. Remove all other PEST variables, se
  8. Hi Petra -- Sounds like a good compromise to reduce the number of model cells. Groundwater modeling always seems to be a series of compromises... Here's the NWT solver settings that Rich passed along. I went back and looked at his description of the settings and he wrote that these settings would be a good starting point for large NWT models, 1.0E-1 1500.0 100 1.0e-8 2 1 1 SPECIFIED CONTINUE 0.90 0.00001 0.000 0.10 0 50 3.0 0.9 linmeth=1 (GMRES); =2 (xmd) 1 0 3 7 1 0.0 1 5.0E-3 1.0e-3 100 XMD I've had good results with these settings and was able to reduce my runtimes.
  9. Hi Petra -- I've been struggling with long run times for a couple of large (up to about 8 million active cell) models, also. I'm doing PEST parameter estimation calibration runs across my local network and see differences in run times depending on the computer capabilities. On older machines (4-5 years old) the run times are usually around 10 hours. On a brand new machine (Dell Latitude - lots of RAM and a fast processor) the run times are about 4 hours. I'm using MODFLOW-NWT and have a unconfined surficial layer and have gotten very good results. I suspect the difference in run times you see
  10. Hi -- Wanted to see if there was a way to designate PEST observation groups directly in GMS. I have tried editing the *.pst file after it's created by GMS but with about 92,000 head observations (from multiple map coverages representing multiple model layers) it quickly becomes problematic.
  11. Hi Sean -- I did the SFR2 package construction all in GMS. The segments have to be in order - from upstream to downstream and the GMS MAP module programming does a good job of this. The trick I found was having a good DEM and matching flowlines to work with. Even with all the prep work we did, there we still some segments that had to fixed by hand.
  12. I'm running with about 8,000 segments in the larger of the 2 model I'm working on. I don't think the type of topography is that important, just get the closed depressions out and make the flowlines match the DEM
  13. Hi Sean -- What we did recently to get the SFR2 package running was mainly a GIS exercise. We simplified and put all of the streams in a "blanket" type surficial layer that covers the entire active model area. Then we put a Digital Elevation Model (DEM) together of the land surface altitudes and and made it match the model grid - grid-wise. Next, use GIS magic to get the sinks (closed topographic) areas out of the DEM. Use more GIS magic to create flowlines from the DEM. We didn't have any luck with the National Hydrography Dataset - the flowlines don't match the topography and you get some ar
  14. FYI - A new version of MODFLOW was posted on the USGS page yesterday: https://water.usgs.gov/ogw/modflow/6beta.html
  15. Hi -- I'm using PEST to estimate MODFLOW Drain Package conductance terms. I have a number of stream gages where I have analysed the data and calculated the groundwater baseflow component and I'm using these data as observations in PEST. In several of the basins, I have 2 (or more) gages and have a question about the PEST variable. In the stream arcs, I'm setting up a negative number in the attribute table for the conductance term (-201, -202, etc). What is the best procedure to use for having the 2 gages in the same basin. What I've done in the past is have 2 separate variables for the 2 gages
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