Page 46 - Beaumont Basin Watermaster

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

1. Deep infiltration of precipitation and runoff in stream channels was fixed at 2012 rates.
Infiltration of areal precipitation represents an 85-yr average hydrology. Infiltration of
runoff in stream channels was adjusted during model calibration to account for increases
associated with land use changes. No further increases in stream channel infiltration
were incorporated into the future projection scenario.

2. Return flow recharge is estimated to require at least 25 years to reach the groundwater
from the time it is applied at the land surface. As such, estimates of return flow recharge
in 2012 are based on land use conditions observed in 1987. As the future projection
simulated in the model is only 20 years, return flow recharge was applied in the future
scenario based on land use conditions observed between 1987 and 2007.

3. By definition, artificial recharge of supplemental water is not included in the Safe Yield
estimate of the Beaumont Basin per Equation 4 above. Although the Little San Gorgonio
Creek Recharge Facility is located outside the Beaumont Basin adjudication area, it is
located over the hydrogeological basin and artificial recharge at this facility becomes
subsurface inflow to the adjudication area. Given that water historically recharged at this
facility has been supplemental water and in keeping with the definition of Safe Yield, no
artificial recharge at the Little San Gorgonio Creek Recharge Facility was simulated in
the 10-yr future projection scenario used to estimate the Safe Yield of the Beaumont
Basin adjudication area.

4. Artificial recharge in the Noble Creek Artificial Recharge Facility was assumed to be 60
percent of SGPWA’s Table A allotment (10,380 acre-ft/yr) minus SGPWA recharge
(1,557 acre-ft/yr) or 8,823 acre-ft/yr. The 60 percent of Table A value was based on
projections of available imported water from SGPWA’s 2010 Urban Water Management
Plan (UWMP). As per Equation 4 above, artificial recharge was subtracted from the
pumping and storage change to estimate the Safe Yield of the Beaumont Basin.

5. Annual Overlyer pumping within the Beaumont Basin was fixed at 2012 rates for the
entire 20-yr projection simulation.

6. Appropriator pumping within the Beaumont Basin was based on water demand
projections reported in UWMPs. For BCVWD, groundwater production in the Beaumont
Basin was based on the total water demand minus Edgar Canyon supplies. Pumping was
allocated among individual Appropriator wells in the same proportions as was reported in
2012. Pumping for SMWC was assumed to remain the same as 2012 pumping rates. The

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