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4 | Groundwater Sustainability Plan for the Yucaipa Basin Area | San Bernardino Valley Municipal Water District
2.2 Sustainability Indicators
This task will document historical and current sustainability indicators as established by SGMA. This
documentation will become the foundation for the development of the sustainability criteria (Task 6). The
team understands that the identification of sustainability criteria is a critical aspect to the development
of the GSP and will be referenced throughout the development process. This process will be stakeholder
driven and two TAC meetings will be dedicated to evaluating and achieving consensus of the historical
water level and water quality conditions of the Yucaipa Basin.

The GSA members have maintained an extensive record of groundwater data from numerous wells in the
Valley. Having prepared a preliminary groundwater model of the basin, Geoscience is very familiar with the
database for the Valley. The results of the 2014 “Safe Yield” study indicated that the basin was in overdraft
for the period of study. The USGS model will be used to further assess the basin conditions with regards
to groundwater overdraft and the other sustainability indicators.

• Groundwater Levels and Storage. Considerable work has been completed to understand the change
in storage in the groundwater basin by Valley District. Current and historical groundwater level and
storage estimates data will be reviewed.
• Water Quality. The existing data will be used to evaluate the ambient groundwater quality as a basis for
evaluation of future projects including recycled water recharge.

• Seawater Intrusion. Although the Yucaipa groundwater basin has no direct hydraulic connection to the
sea, an evaluation of potential brackish water sources potentially from irrigation return flows will be
considered in the analysis.

• Subsidence. The subsurface geologic conditions in the southern portion of the basin indicate the
presence of a well-defined aquitard as well as lenses of materials that may be potentially susceptible
to liquefaction. The USGS model will be equipped with the subsidence package to evaluate potential
subsidence under various planning scenarios.

• Identification of Interconnected Surface Water Streams. Several surface streams are present in Yucaipa
Valley including Yucaipa Creek, Live Oak Canyon Creek, and Wildwood Canyon Creek. These streams
have seasonal flowing water which recharge the groundwater aquifer. However, most of the year there
is a vadose zone between the surface of the stream and the groundwater surface, so basin pumping
does not directly influence the seasonal flow in streams.

• Identification of Groundwater-Dependent Ecosystems. Groundwater-dependent ecosystems will be
identified using available shapefiles generated by projects in the Santa Ana Watershed in combination
with the hydrologic model developed by the USGS.

TAC Meetings Deliverables: TM that will become the “Current
• Evaluation of Historical Groundwater Levels and Historic Groundwater Conditions” chapter
• Evaluation of Historical Groundwater Quality Conditions of the Yucaipa GSP.

TASK 3.0 PLAN AREA including land use
This task provides a description of the plan area for the Yucaipa Basin. Many of the requirements of the
plan area chapter are included in many of the documents already prepared for the Yucaipa Basin and have
been written by the project team. The team will leverage the existing work prepared for the USGS Model,
Regional Urban Water Management Plan, Regional Recycled Water Concept Study, Ambient Water Quality,
Safe Yield, and other studies to efficiently describe the Yucaipa Groundwater Sustainability Plan area.

Deliverables: TM that will become the “Plan Area” chapter of the Yucaipa GSP.
Yucaipa Sustainable Groundwater Management Agency - August 9, 2018 - Page 8 of 208