Page 48 - Beaumont Basin Watermaster

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

7.0 Summary of Findings and Recommendations

A calibrated numerical groundwater flow model of the Beaumont Basin has been updated and
refined based on previous work by the USGS. The updated and refined model is calibrated to
industry standards and is a valuable tool for evaluating both the historical water balance of the
Beaumont Basin and future water balance based on projections of groundwater production and
artificial recharge. Analysis of the Beaumont Basin historical water budget from the
groundwater flow model has resulted in the following findings:

 Between 1972 and 2012 (40-year history), the annualized Safe Yield ranged from
approximately 3,500 to 8,100 acre-ft/yr with a 40-yr average Safe Yield of
5,424 acre-ft/yr.
 Prior to 2000, year-to-year variations in Safe Yield were due primarily to changes in
groundwater pumping within the Beaumont Basin. Years of higher groundwater
pumping generally resulted in the increased capture of groundwater that would have
otherwise migrated out of the basin, resulting in a higher Safe Yield.
 After 2000, increases in groundwater pumping in the Banning area outside the
Beaumont Basin as well as the introduction of artificial recharge within and outside
the basin began to influence the Safe Yield. Although direct correlations between
groundwater pumping and Safe Yield were not possible between 2000 and 2012, the
combination of basin management factors resulted in a Safe Yield increase from
5,123 acre-ft in 2000 to 5,881 acre-ft in 2012.
 Because of recent rapid changes in land use, artificial recharge and pumping in the
Beaumont Basin, estimates of Safe Yield based on the historical water balance are not
representative of the future Safe Yield of the basin.
 Analysis of the Safe Yield of the Beaumont Basin using the groundwater flow model
and based on future projections of artificial recharge and pumping shows that the Safe
Yield can be increased through basin management.
 Analysis of a future basin management projection scenario using the groundwater
flow model resulted in a Safe Yield estimate of approximately 6,700 acre-ft/yr.
 It appears from the analysis of future basin management projection scenarios that
maximum levels of artificial recharge within the basin have the potential to result in
greater subsurface outflow from the basin unless groundwater production is increased
to limit the outflow.

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