Groundwater pumping limits in the San Joaquin Valley A management strategy in the COEQWAL scenario library
This strategy adds limits on groundwater pumping for demand units in the San Joaquin Valley, set at levels estimated to minimize long-term groundwater storage decline. Everything else matches the Current Operations scenario.
This brief describes a scenario that incorporates direct groundwater pumping limits in the San Joaquin Valley, one of 28 management strategies in the COEQWAL scenario library. Each strategy is simulated once under each of five hydroclimates; the references note at the end of this brief lists the model runs.
§2 What this strategy changes
The strategy assigns limits to groundwater pumping in demand units in the San Joaquin Valley. The limits are spatially variable and set according to estimates of the pumping reduction needed to minimize groundwater storage decline over the full 100-year simulation period under a baseline historical simulation. The reductions are implemented via adjusted maximum pumping limits set in lookup tables referenced in the CalSim3 model code. The reductions apply as a fraction of applied water demand for each month and demand unit.
When surface deliveries and the pumping limit together fall short of a demand unit's applied water demand, the remainder appears as a shortage for that unit in that timestep. For example, if a unit's pumping limit is 60% of an applied water demand of 10 TAF, and surface-water deliveries total 3 TAF, groundwater pumping can supply at most 6 TAF and the remaining 1 TAF is recorded as a shortage.
The configuration is meant to mimic, in part, groundwater management actions that may occur under the Sustainable Groundwater Management Act (SGMA). It should not be read as a direct or detailed implementation of that process as it exists now or as it may evolve.
§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.
| Aspect | Current operations | This strategy |
|---|---|---|
| TUCP actions | Active | Active |
| SGMA actions | None | Limit San Joaquin region groundwater pumping |
| Land use | 2020 LandIQ | 2020 LandIQ |
| Delta regulations | Standard | Standard |
| BiOps | 2019 / 2020 ITP | 2019 / 2020 ITP |
| Infrastructure | Standard | Standard |
| Flows | Standard | Standard |
| Allocation / priorities | Standard | Standard |
§4 Lineage and source
This strategy was developed by the COEQWAL team using the COEQWAL Current Operations scenario as the base to which modifications were made. The change is the addition of groundwater pumping limits for San Joaquin Valley demand units, with associated adjustments to weighting, shortage terms, and irrigation water-budget corrections. 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 Farms and groundwater theme brief.
To see outcomes at a specific location of interest, see the relevant LOI briefs — particularly those for groundwater and agricultural locations in the San Joaquin Valley.
References — model runs
Each strategy is simulated once under each of five hydroclimates. The table lists the model run behind this strategy and the current-operations run it is compared against, for each hydroclimate, so any reader can trace this page to specific CalSim runs.
| Hydroclimate | This strategy | Current operations |
|---|---|---|
| Historical hydroclimate (adjusted) | s0025 | s0020 |
| Moderate climate stress (EC-Earth3-Veg) | s0138 | s0134 |
| Moderate-high climate stress (cc50) | s0067 | s0047 |
| High climate stress (cc95) | s0087 | s0056 |
| Extreme climate stress (TaiESM1) | s0112 | s0108 |