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COHYST2010 Groundwater Model: Phase II Summary

COHYST2010 Groundwater Model: Phase II Summary. April 15 th -16 th Lincoln, NE Nebraska Department of Natural Resources. COHYST 2010 - Groundwater Model Phase III. COHYST 2010 - Phase II Groundwater Model Phase III. High resolution “tracking and accounting”

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COHYST2010 Groundwater Model: Phase II Summary

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  1. COHYST2010 Groundwater Model:Phase II Summary April 15th-16th Lincoln, NE Nebraska Department of Natural Resources

  2. COHYST 2010 - Groundwater ModelPhase III

  3. COHYST 2010 - Phase II Groundwater ModelPhase III • High resolution “tracking and accounting” • Refinements to put more confidence of parcel-scale, monthly estimates of impacts to river • Impact of local heterogeneity, detail • Boundary conditions, properties would need to be resolved further for site-specific assessments • CROPSIM process that tracks historic variation as measured

  4. COHYST 2010 - Phase II Groundwater ModelSuccesses&Limitations • Temporal discretization • Type curve stresses distribute extreme events • {Seasons, months, days, years} characterized by anomalous (not following average pattern) pumping, recharge preclude a match in the model • Linkage between slow (gw) and fast (sw, weather) systems • Impossible to fully translate impacts of temporal variability scale without a fully coupled multi-physics model • Not comprehensively understood

  5. COHYST 2010 - Phase II Groundwater ModelSuccesses&Limitations • Temporal & Spatial discretization • Time & space scales related • Point stress propagates quickly, effect local • Regional model suited to longer term, broad stresses • At 2640 ft x 2640 ft, not able to match local impacts from point stress • Can approximate regional-level (township, county, NRD) changes

  6. -Multi-year variability magnitude affected by Sy (aquifer property) -Shape of variability driven by net recharge (CROPSIM)

  7. Sy affects seasonal variability some, but with regional impact

  8. -Drawdown, recovery a local phenomenon (~feet) -1/2 mile grid cells CAN’T match this -Measured water levels reflect myriad factor, not all modeled

  9. -Can approximate local response using “equivalent well block” adjustments -Model contains multi-scale information, possible to project behavior at finer scale as a check

  10. COHYST 2010 - Phase II Groundwater ModelSuccesses&Limitations • History Mismatch - Odessa to Grand Island • Reach known to lose part of year • Target shows losses, although noisy • Simulated baseflow gain/loss • Match gains • Don’t simulate losses • Reasons? • Simulated stages approximately correct, heads high • Initial (head) condition high • Non-stream discharges too low (pumping, GW/surface ET)

  11. COHYST 2010 - Phase II Groundwater ModelSuccesses & Limitations • History Mismatch – Initial Condition • Groundwater system moves slowly • Impacts of decades of GW development being propagated at 1985 • But NOT in dynamic equilibrium • Impossible to fully characterize initial state of system for October 1984 • Where synthetic initial state and boundary conditions/stresses don’t align model takes time to equilibrate

  12. Original Distributed Hydraulic Conductivity

  13. COHYST 2010: Groundwater Model: Key Changes since 2010 • Procedural: • “Warm-up” period – either: • separate synthetic stress periods, or • Beginning years of 1985-2005 model • Calibration tools, metrics • Trend differences • Qualitative, quantitative comparisons • Baseflow targets

  14. COHYST 2010: Groundwater Model: Final Run (22a_17_21) • Adjustments to CROPSIM pumping, recharge, runoff (run 22a – addressed by Marc) • Simulated diversions, returns from STELLA run 17 • Minor QA/QC modifications to boundary condition assignments • Updated K, Sy zonation and preferred values from Roger Miller, Lee Wilson

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