Increase Shasta carry-over storage A management strategy in the COEQWAL scenario library

§2 What this strategy changes

This scenario targets a 20% increase in Shasta Reservoir carryover storage, relative to the Current Operations scenario, via reductions in CVP allocations. Starting in February of each year, estimates of current and projected supply along with empirical estimates of Shasta storage drawdown conditional on the supplies and proposed allocations are used to forecast April and September Shasta storage levels. If a storage shortfall is projected, the allocations are adjusted by a factor tied to that shortfall amount. The calculations and adjustments are updated each month through April. CVP agricultural contractor and Settlement Contractor allocations may be reduced as needed to meet the storage target according to estimated seasonal water supply and projected Shasta storage shortfalls.

Because of uncertainty in water supply at the time allocations are set in CalSim3 — the use of internally generated seasonal forecasts means the model does not “know” how much water the year will bring — the carry-over condition is not guaranteed to be met in a given year.

The modified allocations, Shasta storage, and deliveries may affect hydrology and reservoir conditions in parts of the system not targeted by this strategy's actions. This is a consequence of the interconnections in the Central Valley water management and hydrologic system, as reflected in a complex but incomplete model.

§3 The configuration in detail

The table compares the eight operational fields that define this strategy against current operations — the strategy that represents existing operational rules, recent (2020) land use, and TUCPs. Rows that match current operations are shown in light gray; rows that differ are highlighted.

§4 Lineage and source

This strategy was developed by the COEQWAL team, in part by adapting the allocation logic of USBR's Alt3 (Modified Natural Hydrograph) scenario onto the COEQWAL Current Operations scenario base. This scenario uses DWR's adjusted historical hydrology with the 2020 LandIQ land-use dataset. The CalSim model files for this strategy are referenced by the run IDs in the references note at the end of this brief.

§6 What this doesn't say

This brief describes a scenario representation in CalSim, not a real-world policy proposal or implementation plan. The strategy as modeled may not capture all details necessary to support direct translation to actual operations. The brief does not predict, evaluate, or recommend any outcome — it describes what the scenario changes about CalSim's representation of the system. For what the model produces under this strategy, see the result briefs referenced in §7.

§7 See results for this strategy

To see modeled outcomes under this strategy across all nine key outcomes at the reference hydroclimate, see the The Delta as a living place theme brief.

To see outcomes at a specific location of interest, see the relevant LOI briefs — particularly those for Shasta reservoir and locations on the Sacramento River.

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