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Department of Water Resources Approves New Groundwater Sustainability Plans for Northern California Basins

Department of Water Resources Approves New Groundwater Sustainability Plans for Northern California Basins
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By Elleasse Taylor and Steve Anderson

In January 2023, the California Department of Water Resources (DWR) approved Groundwater Sustainability Plans (GSPs) for four northern California groundwater basins pursuant to the Sustainable Groundwater Management Act (SGMA): Napa Valley Subbasin, Santa Rosa Plain Subbasin, Petaluma Valley Basin, and Sonoma Valley Subbasin. The Groundwater Sustainability Agencies (GSAs) for each subbasin adequately demonstrated to DWR that the GSPs would achieve sustainability for each subbasin as required by SGMA, but DWR identified several corrective actions the GSAs should consider moving forward.


Due to the constant changes in drought conditions and flood water levels, groundwater management is of the utmost importance to water agencies throughout the state. By capturing the groundwater and storing it, agencies can keep water available during drought periods. But to do so, local Groundwater Sustainability Agencies must implement groundwater management plans in accordance with the Sustainable Groundwater Management Act (SGMA).

In 2014, then-Governor Jerry Brown signed SGMA into law. SGMA emphasizes local agencies’ expertise of local groundwater conditions and ability to manage those basins, either singly or jointly. Among other things, SGMA requires local agencies to form GSAs for basins experiencing moderate to severe overdraft, which occurs when groundwater withdrawal exceeds recharge and can lead to negative impacts like subsidence (sinking of land), poor groundwater quality, and insufficient water supplies for beneficial uses. GSAs are required under SGMA to develop and implement Groundwater Sustainability Plans to achieve sustainability in overdrafted groundwater basins within a 20-year time horizon. Each GSP has its own goals specific to the covered groundwater basin and must be accomplished within the 20-year period. To achieve the sustainability goal for the Subbasin, the GSP must demonstrate that implementation of the Plan will lead to sustainable groundwater management, which means the management and use of groundwater in a manner that can be maintained during the planning and implementation horizon without causing undesirable results, such subsidence, water quality degradation, and lowering of groundwater levels. Undesirable results must be defined quantitatively by the GSAs.

To date, the Department of Water Resources, which is tasked with reviewing GSPs, has approved several GSPs but has also deemed many to be inadequate, thus requiring additional plan development to achieve sustainability. Many more GSPs are still under review. DWR’s review considers whether there is a reasonable relationship between the information provided and the assumptions and conclusions made by the GSA, including whether the interests of the beneficial uses and users of groundwater in the Subbasin have been considered; whether sustainable management criteria and projects and management actions described in the GSP are commensurate with the level of understanding of the Subbasin setting; and whether those projects and management actions are feasible and likely to prevent undesirable results. To the extent overdraft is present in a subbasin, DWR evaluates whether a GSP provides a reasonable assessment of the overdraft and includes reasonable means to mitigate the overdraft. DWR also considers whether a GSP provides reasonable measures and schedules to eliminate identified data gaps. DWR is also required to evaluate whether the GSP will adversely affect the ability of an adjacent basin to implement its GSP or achieve its sustainability goal.

GSAs are required to evaluate their GSPs at least every five years and whenever a GSP is amended, and to provide a written assessment to DWR. Accordingly, DWR will evaluate approved GSPs and issue an assessment at least every five years. To that end, SGMA provides a process for local GSAs to follow to ensure water data is gathered and stored properly to facilitate adaptation of groundwater management based on climate and water level changes, which in turn allows local agencies to better curate plans for their specific region as conditions shift. The process helps ensure groundwater management accounts for uncertainties resulting from climate changes and drought shifts.

The Approvals

DWR approved GSPs for the Santa Rosa Plain Subbasin, Petaluma Valley Subbasin, Napa Valley Subbasin, and Sonoma Valley Subbasin. A single GSP was submitted by the applicable GSA for each subbasin. Each approval was based on DWR’s determination that the GSP satisfied the objectives of SGMA and substantially complied with GSP regulations. Specifically, DWR issued a statement of findings for each GSP. Notably, DWR found that the Santa Rosa Plain Subbasin GSP would be closely coordinated with the neighboring GSAs in Petaluma Valley and Sonoma Valley, and that the GSP did not appear to adversely affect the ability to implement the GSPs for those subbasins or impede achievement of sustainability goals in those adjacent basins. DWR also recognized that the eight member agencies of the Santa Rosa GSA historically implemented numerous projects and management actions to address problematic groundwater conditions in the subbasin, and that the GSA reasonably demonstrated it had the legal authority and financial resources to implement the GSP. DWR made similar findings for the other GSPs.

However, DWR also recommended a number of corrective actions for each GSP and strongly encouraged each GSA to consider and implement those actions. For instance, DWR recommended that each GSA: (1) identify certain surface water imports; (2) provide additional details and discussion related to specific components the GSA used to establish chronic lowering of groundwater levels sustainable management criteria; (3) continue to fill in data gaps, collect additional monitoring data, coordinate with resource agencies and interested parties to understand beneficial uses and users that may be impacted by depletions of interconnected surface water caused by groundwater pumping, and potentially refine sustainable management criteria; and (4) provide additional details related to monitoring networks. DWR’s recommendations, while different for each GSP, are focused on obtaining increasingly detailed information about the relationship between surface water availability and groundwater use (e.g., from the Russian River), operational responses to chronic lowering of groundwater levels exacerbated by prolonged periods of drought, and impacts on interconnected surface and groundwater related to pumping.

DWR emphasized that this type of information be captured and made available to assist DWR in its five-year review of the GSPs to ensure that the GSPs are on target for achieving sustainability of the groundwater basins within the time horizon set under SGMA. In sum, DWR approved the GSPs but clearly indicated its focus on detailed hydrological information demonstrating whether sustainability would be achieved moving forward as required by SGMA.

Conclusion and Implications

The Department of Water Resource’s approval of the four GSPs in northern California are a positive sign for groundwater sustainability management in the region. However, DWR’s continuing oversight role in actually achieving sustainability is clear in its approval of the GSPs. It remains to be seen to what extent the GSAs will pursue or satisfy the corrective actions recommended by DWR, and what role accomplishing those actions will play in DWR’s subsequent review of the GSPs in five years. For more information, see: DWR Approves GSPS For Four Northern California Basins (Jan. 26 2023)