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Groundwater Model Update COHYST2010

Groundwater Model Update COHYST2010. December 17-18 th , 2012 HDR Offices – Omaha, NE Nebraska DNR James Gilbert, Mahesh Pun, Ruopu Li, Jesse Bradley, Jim Schneider. Monday 12/17 – Morning Discussion. Groundwater Model Report: Review of work done since 11/2/2012 Workshop

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Groundwater Model Update COHYST2010

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  1. Groundwater Model UpdateCOHYST2010 December 17-18th, 2012 HDR Offices – Omaha, NE Nebraska DNR James Gilbert, Mahesh Pun, Ruopu Li, Jesse Bradley, Jim Schneider

  2. Monday 12/17 – Morning Discussion • Groundwater Model Report: • Review of work done since 11/2/2012 Workshop • Optimization/PEST - Recharge • Scenario structure • Target Review • Status of Model – Results Unique to GW model • Head calibration • Trends • Residuals

  3. GW Model: Progress Since November • Inverse model runs – Recharge • Goal: improve GW model & STELLA head, flux, and flow calibration • Using: 1) CROPSIM-consistent soil zonation (3, then 9 from 17) 2) PEST optimization of GW model using recharge multipliers

  4. GW Model: Progress Since November3-Zone Recharge Optimization (11/16 – 11/30)

  5. GW Model: Progress Since November3-Zone Recharge Optimization (11/30/2012) • 3- Zone Optimization Results: • Increase Sandhills recharge • Decrease recharge everywhere else • Challenge to resolve North-South trend discrepancies

  6. GW Model: Progress Since November9-Zone Recharge Optimization (based on 17 CROPSIM zones)

  7. GW Model: Progress Since November9-Zone Recharge Optimization (12/6/2012) • 9- Zone Optimization Results: • Increase recharge in Sandhills area north of North Platte (zone 3) • Decrease recharge everywhere else (except spurious zone 1 Platte Valley) • Again, challenge to resolve North-South trend discrepancies; “problem” area in SW Custer/NW Dawson counties

  8. GW Model: Progress Since November9-Zone Recharge Optimization (based on 17 CROPSIM zones)

  9. GW Model: Progress Since NovemberRevised9-Zone Recharge Optimization (12/12/12) • Revised 9- Zone Optimization: • Held Kx in Platte River Zone 5 Constant at 61 ft/d • Results: • Decrease recharge everywhere except Zone 4 (Perkins, SW Lincoln counties) • Manual adjustments to recharge multiplier in SW Custer Co did little to affect trend differences • Suspect issue with boundary conditions in region

  10. Recharge Optimization Conclusion • Head residuals and trend differences reduced by model-wide reduction in recharge • Outbasin flux calibration improved through reduction of recharge in Blue Basin area • Mainstem Platte flux calibration mostly insensitive to reduction in RCH • Outcome: • CROPSIM Run019 – reduced recharge

  11. CROPSIM Run019 and Kx Optimized – Outcome12/13/2012 • Head calibration • Areas of improvement (Blue Basin, south central model area) • Remaining issue areas • Outbasin Fluxes

  12. Head Trends Progress– Early Sept 2012

  13. Head Trends Progress– CROPSIM Run019, Dec 2012

  14. Head Trends Progress– CROPSIM Run019 (Kx optimized, zone 5 Kx constant), Dec 2012

  15. Head Trends Progress– CROPSIM Run019, Dec 2012 – Censored Calibration Window (1990-2005)

  16. Head Trends Progress– CROPSIM Run019 (Kx optimized, zone 5 Kx constant), Dec 2012 – Censored Calibration Window (1990-2005)

  17. CROPSIM Run019 and Kx Optimized – Outcome12/13/2012 • Head calibration – remaining issues: • SW Custer, NW Dawson counties • Perkins & Clay county clusters • 50 worst head trend sites – what is good enough? • Outbasin Fluxes: • In ballpark with most using Run019 RCH • Close enough given uncertainty and location outside area of interest?

  18. GW Model: Platte Fluxes, Issues • Platte river flux (baseflow) calibration • Adjustments made to STR package • Targets (focus on Reach 1) • SPR, Roscoe to NP • Proposed revisions • History matching • Cumulative, seasonal, annual • Issues • Critical for model purposes • Acceptable - Explain and justify

  19. GW Model: Baseflow to North Platte • Adjustments • Moved Sutherland return point downstream to be closer to actual geographic location • Resolved runoff, canal return routing mistake on North Platte River • Effect on baseflows minor, but ensures conceptual and geographic consistency

  20. GW Model: Baseflow to North Platte • Baseflow Targets: • Error in Roscoe to North Platte reach • Result of inconsistent filtering between upstream, downstream gage locations – introduced erroneous shift • Resolved by ensuring baseflow gain does not exceed total flow gain • Resolved issue of negative runoff by assigning all losses as baseflow • Previously losses, as with gains, were partitioned into a runoff and baseflow component

  21. GW Model: Baseflow to North Platte • Baseflow Targets: • In process of applying total flow gain check on all reach targets • so far only SPR Roscoe-North Platte seems to have been affected • The moving average smoothing was applied when the goal was a “less flashy” target • Model only simulated baseflow gain or loss from Platte using baseflow-derived stage (very minor stage variability  very minor baseflow fluctuations) • Now model “sees” all the water that actually is in the river- variability in stage and target now appropriate • Solution: Revert back to un-smoothed targets

  22. Reach 1 and Other Hydrographs • PDFs of baseflowhydrographs • Time series – by season • Hydrograph_20121215_Flux.pdf • Hydrograph_20121215_Flux_Irrig.pdf • Hydrograph_20121215_Flux_nonIrrig.pdf • Cumulative – by season • Hydrograph_accu_20121215.pdf • Hydrograph_accu_20121215_Irrig.pdf • Hydrograph_accu_20121215_NonIrrig.pdf

  23. Issues • Critical • Potential boundary condition issue in SW Custer Co • Baseflow and runoff targets – GW model contribution to integrated model • Do sites with large head residuals indicate a local/regional problem? • Convergence issues with Kx-optimized Run19_06_13 • Informational • Stage variability in STR • ET in Platte Valley • Baseflow losses on north side Platte tributaries

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