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per GSP Regulations Subarticle 3, § 354.22‐§ 354.30. This evaluation allows identification of metrics
under which the sustainability indicators become significant and unreasonable, thereby defining
undesirable results. This metric is referred to as a minimum threshold and will be developed for each
sustainability indicator applicable to the YGSA. Measurable objectives will be identified to demonstrate
future performance and ability to achieve the sustainability goal.
Analysis of undesirable results will build on results of the previous tasks and be used to determine
minimum thresholds and measurable objectives. It will involve focused discussion of groundwater
conditions with respect to the six undesirable results (only four of which may be applicable or significant
to YGSA), the related beneficial uses and users, and the potential effects (existing, projected, and
cumulative) of groundwater conditions on beneficial uses/users.

Analysis of undesirable results will be accomplished through various analytical and numerical
assessments. For chronic lowering of water levels, the analysis will focus on historical and current water
level contour maps and well hydrographs, with comparison to potentially affected wells. Depletion of
groundwater storage will be evaluated with the USGS model and supplemented by findings from
previous evaluations to ensure availability of supply through drought and climate change. Potential
groundwater quality degradation will involve analysis of water chemistry with depth, overall
groundwater quality, and constituents of concern, but are likely to be readily managed. Subsidence is
not expected to be a critical sustainability indicator but will be assessed using data provided by DWR and
USGS California Water Science Center. Historical low water levels may provide a reasonable minimum
threshold. Identification of interconnected surface water systems will be assessed with the USGS Model,
and identification of GDEs will be based on review of GIS mapping and DWR‐provided data. Preliminary
review of depth to water indicates that sustainability indicators for interconnected surface water
systems and GDEs are likely to be constrained to the northern and eastern margins of the Basin.
The GSP draft regulations outline how minimum thresholds are defined with regard to supporting
information, their mutual inter‐relationships, relation to existing regulations, consistency with the
monitoring program, and effects on beneficial uses across the basin. Consistent with GSP regulations,
minimum thresholds will be identified for each of the sustainability indicators in each management area,
if more than one such area is defined for the YGSA.

Task 4 – Identify and Evaluate Management Actions

We will collaborate with YGSA to develop and analyze projects and management actions to achieve the
identified sustainability goal (and interim goals) per GSP Regulations Subarticle 5, § 354.42– 354.44.
Once groundwater sustainability has been defined, measurable objectives identified (including minimum
thresholds), and the water budget established, sufficient information will exist to assess groundwater
conditions relative to the sustainability goal. It is at this point that an implementation program is
developed and presented in the Management Actions and Projects sections of the GSP.
The development of projects and management actions will be tied closely to sustainability criteria
developed in Task 3. A range of possible management actions, programs, and projects will be identified
(based on existing planning documents, ongoing investigations, and outreach) that can be implemented
to help achieve (or maintain) sustainability. Projects will be screened for feasibility and ability to meet
the GSP objectives. Individual projects will first be simulated using groundwater modeling to assess the
ability to meet the sustainability goal; promising projects will be re‐analyzed as scenarios for GSP
development. Although projects and actions will be evaluated during a public process, some key

Proposal – SBVMWD Groundwater TODD GROUNDWATER
Sustainability Plan for the Yucaipa Basin Area 6 June 2018
Yucaipa Sustainable Groundwater Management Agency - August 9, 2018 - Page 153 of 208