Page 42 - Beaumont Basin Watermaster

Beaumont Basin Watermaster
2013 Reevaluation of the Beaumont Basin Safe Yield 3-Apr-15

Where:

2
C = Streambed conductance, (ft /day)
K = Vertical hydraulic conductivity of streambed, (ft/day)
L = Length of reach, (ft)

W = Width of stream, (ft)

M = Thickness of streambed, (ft)

5.9 Model Calibration

The transient groundwater flow model was calibrated to groundwater levels measured in selected
monitoring wells from January 1927 through December 2012. Target monitoring wells for the
model calibration are shown on Figure 36.

5.9.1 Calibration Process

The groundwater flow model was calibrated by matching model-generated groundwater levels
with measured groundwater levels at the monitoring wells shown on Figure 36. Calibration was
initially achieved through a trial-and-error process by adjusting various model parameters, within
accepted ranges, until an acceptable groundwater level match was achieved. Parameters that
were adjusted included horizontal hydraulic conductivity, vertical hydraulic conductivity,
storativity, specific yield, GHB conductance and barrier conductance.

Once the initial calibration resulted in a relatively good match between model-generated and
measured groundwater levels, the calibration was further refined using PEST. The PEST
calibration involves varying multiple combinations of input parameters in the model within
specified acceptable ranges until the model achieves the best fit possible between model-
generated and measured groundwater levels. Details of the theory and methodology of the PEST
process are described in Doherty (2002).

5.9.2 Transient Model Calibration Results

Measured versus model-generated groundwater levels for 16 target wells are shown on
Figure 37. Calibration hydrographs are provided in Appendix H. The calibration is based on
6,278 groundwater levels measured between January 1927 and December 2012. The solution for
the final calibrated model successfully converged at a head-change criterion of 0.01 ft.

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