A closer look at State Water Board probationary hearing staff reports.
By Natalie Willis, Reporter, Valley Ag Voice
Despite varying interests and distinct stakeholder needs, one thing Groundwater Sustainability Agencies can collectively agree on is the need to avoid a probation determination from the State Water Resources Control Board.
Of the six critically overdrafted basins in the Central Valley, only the Tulare Lake Subbasin has officially been placed on probation. While the six basins cover different areas with unique water needs and landowner interests, there are several commonalities in the deficiencies the SWB found within the separate groundwater sustainability plans.
State Water Board staff has released three probationary hearing draft staff reports for the following basins — Tulare, Tule, and Kaweah. The subbasin GSPs share three specific inadequacies: chronic lowering of groundwater levels with insufficient Sustainable Management Criteria, continued land subsidence, and further degradation of groundwater quality.
LOWERING GROUNDWATER LEVELS
According to the SWB reports, achieving the sustainability objective for a basin under SGMA includes the lowering of groundwater levels as it can cause shallow wells to go dry or reduce their productivity.
For both the Tule Subbasin and Kaweah Subbasin — which will have their probationary hearings on Sept. 17 and Nov. 5, respectively — the Department of Water Resources identified three key deficiencies related to the chronic lowering of groundwater levels.
The lowering of groundwater levels indicates a “significant and unreasonable” depletion of supply, according to SWB staff. Three key deficiencies for this management criteria found within Tule and Kaweah Subbasin GSPs include insufficient goals within the GSP that allow significant impacts on domestic wells, GSP goals do not achieve sustainability, and the GSPs plan to measure progress against modeled projections rather than goals that achieve sustainability and avoid harm caused by declining groundwater levels.
Tulare Lake Subbasin’s GSP was labeled with similar deficiencies in the chronic lowering of groundwater levels. Staff concluded that the most recent GSP submitted in 2022 did not justify its approach to lowering groundwater levels, and as such was recommended for probation.
For Tule and Kaweah, SWB staff offered recommendations to address this deficiency, calling for revisions to both GSPs’ goals so that they prevent overdraft, revise how sustainability progress is measured, do not allow significant and unreasonable impacts, and add details to well mitigation and demand management plans.
LAND SUBSIDENCE
Another consideration under SGMA is avoiding “significant and unreasonable” land subsidence that interferes with surface land uses. Simply stated, subsidence is the sinking of land as a result of groundwater removal — land subsidence from excessive groundwater extraction often leads to irreversible damage to infrastructure and aqueducts.
To avoid probation, the Tule and Kaweah GSPs must clearly define how they will avoid the effects of land subsidence on critical infrastructure and ensure sustainability goals are consistent with avoiding subsidence impacts.
SWB staff built upon DWR’s analysis that subsidence in the Tule and Kaweah subbasins may greatly impact the Friant-Kern Canal which delivers irrigation water to over 1 million acres of farmland.
The staff reports recommend that the GSAs develop and implement plans that avoid significant impacts on critical infrastructure due to subsidence. The Tulare Lake Subbasin’s GSP failed to revise its subsidence-based inadequacies before its hearing in April.
GROUNDWATER QUALITY DEGRADATION
The degradation of water quality relates to the local drinking water supply as SGMA requires GSAs to consider the interests of all groundwater uses, including municipal well operators and public water systems.
While the DWR analysis on Degraded Water Quality in the Kaweah Subbasin’s GSP did not list any deficiencies, the water board staff are concerned about the “potential impacts” that the subbasin’s management actions would have on drinking water and, as such, listed it as a reason for probation.
“The GSP’s goals are not well described, so it is unclear if the goals would prevent significant and unreasonable impacts,” the staff report said.
The DWR analysis for the Tule Subbasin, however, did list its degraded water quality section as insufficient. Reasons included not specifying which groundwater conditions are suitable for agricultural irrigation and domestic users, not explaining how using a 10-year running average for sustainable management criteria will avoid undesirable results, and failure to explain how the criteria relate to existing groundwater regulatory requirements in the subbasin.
Tulare Lake’s 2022 GSP did not adequately address its approach to Degraded Water Quality, thereby failing to remedy the third deficiency outlined by DWR.
INTERCONNECTED SURFACE WATER
The Tule and Kaweah GSPs had a fourth deficiency not included in the Tulare Lake Subbasin staff report — depletions of interconnected surface water.
Again, the DWR analysis on the Kaweah Subbasin GSP did not include this as a deficiency in their inadequate determination and acknowledged that while the section was not fully consistent with GSP Regulation requirements, the GSA’s efforts to address the deficiency are adequate.
SWB staff took a reversed stance, claiming that while they acknowledge Kaweah Subbasin’s efforts to address data gaps related to interconnected surface water depletions, the current GSPs do not meet SGMA requirements.
The Tule Subbasin also does not have an adequate plan to address the depletion of interconnected surface water to achieve groundwater sustainability by 2040.
