Page 12 - Beaumont Basin Watermaster

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

Safe Yield = S + O p - I ar (4)

This relationship is valid if the following conditions are met:

1. The Safe Yield incorporates a hydrology that is representative of a relatively long period
of record that includes multiple wet and dry hydrologic cycles.
2. The land use conditions are representative of the time period.
3. Pumping and recharge within the basin does not result in adverse impacts.

The approach used to reevaluate the Safe Yield of the Beaumont Basin was to use the calibrated
numerical groundwater flow model to simulate future projections of groundwater pumping and
artificial recharge in the context of a long-term average hydrology and return flow based on
projected land use conditions. The Safe Yield was estimated for the 10-yr period from 2013 to
2022 based on the projected water balance for this period from the calibrated model and
Equation 4 above.

1.4 Summary of Updates and Refinements to Existing Models

In order to use the existing USGS groundwater flow model for the Safe Yield reevaluation, it
was necessary to update and refine the model. The previous model (Rewis et al., 2006) was
calibrated from 1927 through 2003. For this analysis, the model was updated with pumping,
recharge and other data through December 2012. Model refinements included:

1. Expansion of the groundwater flow model area to incorporate the entire Beaumont
Basin adjudicated area and immediate surroundings consistent with the
hydrogeological basin.
2. Reorientation of the model grid to be north-south/east-west to match the surface water
model grid.
3. Refinement of the model grid from 200 meter squares to 50 meter (164 ft) squares.
4. Incorporation of monthly stress periods from 2003 through 2012.
5. Modification of layer boundaries consistent with data collected since 2003.
6. Modification of aquifer properties consistent with data collected since 2003.
7. Changes in the location and rate of areal recharge consistent with changing land use
conditions.

A detailed discussion of the updated and refined groundwater flow model is provided in
Section 5.

4