Local Groundwater Flow Model Addendum Guadalupe Restoration Project San Luis Obispo County October

Reasons for LGFM Revision Excess water entering DSA from agricultural fields to the east Drainage channel along eastern DSA identified Update layer structure to conform with new data Overall goals: more realistic water balance, enhance model reliability

Model Revisions Changed layer structure –Base of DSA revised throughout GOF –Top of PA conforms with Worts (1951) Included agricultural drainage channel Revised recharge and soil properties for agricultural fields Revised calibration targets and improved model calibration

Revisions to Layers

Old Layer 5 Bottom (gray) New Layer 5 Bottom (colored) Old DSA Bottom (gray) New DSA Bottom (colored)

Old PA Top (gray) New PA Top (colored)

Addition of Agricultural Drain

Drain Location in LGFM 3.0 Agricultural Fields DSA

Changes to Recharge and Soil Properties

Recharge Rates in LGFM in/yr 8 in/yr 10.7 in/yr

Recharge Rates in LGFM in/yr 8 in/yr 3 in/yr

Hydraulic Conductivities in LGFM 2.0 K h = 75 ft/day K v = 33 ft/day K h = 50 ft/day K v = 5 ft/day

Hydraulic Conductivities in LGFM 3.0 K h = 75 ft/day K v = 33 ft/day K h = 25 ft/day K v = 2.5 ft/day

Calibration

Recalibration Statistics

How Has Flow Balance Changed? Bottom Outflow Bottom Inflow Lateral Outflow Lateral Inflow Outflow to River Willows Outflow Recharge Inflow Evapotranspiration Outflow Drain Outflow

Flow Balance: Old vs. New

Conclusions Model is more realistic in several ways: –layer structure –drain and river –agricultural fields –water balance Complies better with conceptual model

Conclusions Model represents shared vision Will provide better predictions of groundwater flow for future characterization and remediation issues