In January of this year, the Kings and Tulare Lake Subbasin Groundwater Sustainability Agencies (GSAs) were notified by the Department of Water Resources (DWR) that their Groundwater Sustainability Plans (GSPs) were incomplete. DWR identified several deficiencies in the GSPs. Below is a summary of the responses to DWR’s identified deficiencies in the Kings and Tulare Lake Subbasin GSPs.
KINGS SUBBASIN RESPONSES
The Department of Water Resources centered their comments of the Kings Subbasin GSPs around the Sustainable Management Criteria. The deficiencies covered four main topics: groundwater levels, land subsidence, interconnected surface water systems, and water quality.
Deficiency – Groundwater Levels: GSPs do not set Sustainable Management Criteria for chronic lowering of groundwater levels in a manner consistent with the requirements of SGMA and the regulations.
Response: Changes to the GSPs included adding language stating groundwater levels will decline in dry periods to a point that they will not likely recover during normal/wet periods and a significant and unreasonable number of shallow domestic wells will go dry. A Shallow Well Mitigation Program was added to the GSPs.
Deficiency – Subsidence: GSPs do not set Minimum Thresholds and Measurable Objectives for subsidence in a manner consistent with their undesirable result definition, SGMA requirements, and GSP regulations.
Response: Primary concern is loss of capacity in gravity flow water conveyance systems. Changes to the GSPs include focus on impacts on infrastructure on main irrigation canals based on canal capacity. It was noted that the Subbasin does not have good data on confined aquifer pumping.
Deficiency – Interconnected Water Systems: GSPs do not consistently identify interconnected surface water systems, or provide the location, quantity, and timing of depletions of those systems due to groundwater use. The GSPs do not define Sustainable Management Criteria for the depletions of interconnected surface water in the manner required by the regulations.
Response: Much of the language in the GSPs was revised to list this as a data gap. A plan was included to gather missing information and determine extent of interconnection, as well as estimate of possible groundwater pumping.
Deficiency – Water Quality: GSPs do not provide adequate information to support the selection of degraded water quality Sustainable Management Criteria.
Response: Language was revised to be more specific about the determination of undesirable results. Water quality data will be collected annually and compared against Minimum Threshold levels. If there is an exceedance, site-specific investigation will try to determine if GSA actions have contributed to groundwater quality degradation, and if so, management actions would be implemented.
TULARE LAKE SUBBASIN RESPONSES
The Department of Water Resources centered their comments of the Tulare Subbasin GSP around the Sustainable Management Criteria. The deficiencies covered three main topics: groundwater levels, land subsidence, and water quality.
Deficiency- Chronic Lowering of Groundwater Levels: The GSP does not address potential impacts of dewatering wells in the context of the undesirable result of significant and unreasonable depletion of supply associated with the chronic lowering of groundwater levels.
Response : The GSAs will implement a well registry of active wells locations and their construction information. The information will provide additional clarification on the amount of pumping in each aquifer zone. Each GSA will prepare a mitigation plan to address impacted wells following the general requirements of the Mitigation Plan Framework. The GSAs are seeking to coordinate these mitigation programs.
Deficiency- Chronic Lowering of Groundwater Levels: The GSP does not set Sustainable Management Criteria for chronic lowering of groundwater levels in a manner consistent with the requirements of SGMA and the regulations.
Response: The methodology used to calculate the Minimum Threshold (MT) has been updated. The revised approach for developing the Sustainable Management Criteria (SMC) is based on a regional analysis of aquifer and well completion depths. This method defines a mapping framework within which the groundwater level SMC is defined. The groundwater infrastructure used to access the groundwater beneficial uses has been statistically analyzed using DWR’s database of well completions in the Subbasin. The MTs were set to be protective of 90% of wells listed in the database.
Deficiency- Land Subsidence: The GSP does not define undesirable results or set sustainable management criteria for subsidence in the manner consistent with SGMA and the GSP Regulations.
Response: Addressed using a risk assessment approach by combining the key elements of subsidence. MTs were set for total subsidence to be protective of infrastructure with “early warning” monitoring based on differential subsidence. Areas where impacts are most likely occurring will be identified through the risk framework. Local-scale minimum thresholds are defined that relate to specific infrastructure tolerances. Additionally, a regional scale risk framework is defined to identify areas that are most prone to undesirable results.
Deficiency- Water Quality: The GSP does not identify sustainable management criteria for degraded water quality. The reliance on existing regulations and policies to define undesirable results that represent degraded water quality conditions occurring throughout the Subbasin for the purposes of SGMA does not satisfy the requirements of the GSP Regulations.
Response: The SMCs for each constituent of concern (COC) were developed using the most stringent water quality goal. Ongoing evaluation will be based on utilizing statistical analysis for establishing concentration limits and trend analysis to evaluate COCs annually. Under this approach, an undesirable result for degraded water quality may be triggered and protective efforts will be implemented if the statistical assessment conducted each year indicates an upward trend of one or more COCs.
Both Subbasins submitted their revised GSPs to the Department of Water Resources prior to the July 27 deadline. As August 1st, the public can comment on the updated Kings and Tulare Lake Subbasin GSPs on DWR’s SGMA Portal. The public comment period will last for 60 days and close on September 30.