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SGMA Inadequate Subbasins Update

There is intense activity going on right now in the Groundwater Sustainability Agencies (GSAs) whose plans were deemed “inadequate” by the Department of Water Resources (DWR) this past spring. Sustainable Groundwater Management Act (SGMA) enforcement for the six inadequate subbasins was transferred to the State Water Resources Control Board (SWRCB).


A SWRCB staff report to the State Board last month had this summary: “the six basins with inadequate GSPs, from north to south, are the Chowchilla, Delta-Mendota, Kaweah, Tulare Lake, Tule, and Kern County subbasins. Deficiencies DWR noted include, but are not limited to, insufficient sustainable management criteria, the potential for dewatering of drinking water wells, impacts of subsidence, and lack of coordination amongst GSAs.”


The SWRCB staff has put out a schedule for conducting a “probationary hearing” for each of the subbasins starting in December of 2023 with the Tulare Lake Subbasin, then the Tule Subbasin in January 2024, the Kaweah Subbasin in March and the Kern Subbasin in April, the Delta Mendota Subbasin in May and the Chowchilla Subbasin in June 2024. It is important to note that while there are multiple Groundwater Sustainability Agencies in each of these Subbasins, the State is treating each subbasin as a unit.


Here is what I am learning from the public meetings I attend about where these subbasins are in addressing the items identified by DWR.


Tulare Lake points out that their GSP set minimum thresholds (MTs) at groundwater levels that would be protective of domestic wells. DWR criticized them for not considering agriculture and industrial wells in setting minimum thresholds, but the Tulare Lake folks pointed out that the domestic wells were shallower so by protecting the domestic wells they are also protecting the deeper ag and industrial wells. The subsidence deficiency is much harder to address and given the public attention subsidence in Tulare Lake received over the past number of months, this issue will require significant work to address. It is pretty well known that subsidence is caused by pumping from below the Corcoran clay in the deep aquifer. There is and has been a lot of groundwater production from those deep wells. The Tulare Lake technical people have been given the task of understanding how much production is occurring below the clay for the purpose of eventually determining how much this production must be curtailed to slow down and eventually stop subsidence.


At the Tule Subbasin, most of the GSAs set very low MTs. However, one GSA in Tule set their MTs higher. This presents a coordination problem right off the bat. The GSA that set the higher MT has access to a lot of surface water; the other GSAs have less surface water. So, coordinating the MTs in the subbasin is job one. It is likely the MTs will have to be significantly raised to satisfy the SWRCB. This will likely have an impact on how much overdraft will be allowed in the transition period from now until 2040 when SGMA requires everyone to be sustainable. The subsidence issue is also a big deal in the Tule Subbasin. The technical people are in the middle of trying to understand the amount of pumping below the Corcoran clay and devise a strategy to reduce that pumping and slow down the rate of subsidence with the goal of eventually eliminating it. One other wrinkle that could become an issue: The GSA with the good surface water supply had agreed to cover about 7,500 acres of irrigated land that was outside of their boundaries as part of their GSA on behalf of Tulare County. Two weeks ago, the GSA terminated that agreement and is no longer willing to cover those 7,500 acres. SGMA requires all land in the Subbasin to be covered by a GSA. If another GSA does not cover those 7,500 acres then the subbasin for that reason alone would be in probation.


The three GSAs in Kaweah Subbasin were not coordinated in their MTs. They have now brought in additional technical resources, and those engineering firms, with the managers, are working collaboratively to update their hydrologic modeling with the goal of being able to adjust MTs for water levels and subsidence that will allow them to come back into compliance. The modeling work is not completed. When it is, folks will have to see what adjustment to pumping plans will have to be made to comply with the new MTs for both water levels and subsidence. They are also working on implementing domestic well mitigation programs. Those are out for public comment right now.


The Kern Subbasin has about 19 GSAs and submitted at least five Groundwater Sustainability Plans (GSPs). They cover over 1 million acres and are not coordinated in their MTs. Kern is a complicated subbasin with access to significant local, state and federal surface water resources. They also have significant groundwater banking operations. A formal coordination committee has been established and is the vehicle for bringing all of the various parts of the subbasin together. There are several highly capable hydrologic engineering firms that are working collaboratively to develop a common approach for setting subbasin-wide MTs. The goal is to have the technical people start the process and propose options that the GSAs can evaluate for impacts to their specific area. The hope is that they will be able to find a unified approach that everyone can live with. While SGMA promotes local control, it requires coordination within a subbasin with your neighbors. Different GSAs are in very different positions with regards to their water supplies. Finding a common approach will require painful choices.


The Delta Mendota Subbasin has 19 GSAs and lack of coordination between their GSPs in addressing MTs was the major concern of DWR. The Delta Mendota Subbasin spokesman at the SWRCB meeting last month said that they were reorganizing and committing to put together a single GSP for the entire subbasin that will address the coordination issue as well as coming up with MTs that will meet the requirements. The State Board members were quite complementary of that direction, but of course it will take enormous effort to get everyone on the same page.


The Chowchilla Subbasin took a very aggressive approach. Chowchilla decided to adopt the Merced Subbasin approach which had been accepted by DWR and essentially raised their MTs to 2015 groundwater levels. This is a very ambitious MT level considering that current groundwater levels in much of Chowchilla are BELOW those MTs and will therefore need to be raised in order to meet the MT requirement. For this, Chowchilla proposes interim milestones that will require the raising of water levels over the next 17 years. The Chowchilla GSAs also made a commitment to slow the rate of subsidence over the transition period to essentially zero. A domestic well mitigation plan was also developed. All these changes were adopted by the Chowchilla GSAs very quickly and submitted to the State Board staff for feedback. That feedback was as follows: The State Board was concerned about the ability of Chowchilla to actually raise their water levels in the interim. They wanted more explanation about how the GSA planned to slow the rate of subsidence and they really disliked the $30,000 per well cap on spending to mitigate a dry domestic well. So, more work to do.


These subbasins find themselves in a very difficult position. Regulating groundwater under SGMA is a new process and so there are no historical precedents to reference. The State Board members ultimately hold the power to vote to put a subbasin under probation which would trigger a direct relationship between landowners and the state. There is not a lot of clarity about how this would work and there is great fear that going down this route will stop much of the very positive momentum toward sustainability that has been achieved already. My assessment is that everyone is genuinely working to reach sustainability. Unfortunately, these are very tough situations and as human beings we tend to try to avoid painful decisions. SGMA at its core is about allocating pain. The inadequate subbasins are living that reality right now. I continue to be impressed by the people engaged in this process. Folks are taking it seriously and making hard choices. I continue to be optimistic that in the end we will get where we need to be.








Geoff Vanden Heuvel

Director of Regulatory and Economic Affairs

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