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Tri County Water Authority May 26, 2021

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TechnofloThe Tri County Water Authority held its Advisory Committee meeting on Wednesday, May 26, 2021 on Zoom from its Corcoran offices. The meeting was scheduled to begin at 10:00am and I have no reason to doubt that it did start then. I was having trouble getting in through Zoom and arrived a bit late.

The Meeting

When I tuned in Geosyntec Engineering’s Amir Hussain was talking about land retirementw funds in Governor Gavin Newsome’s budget. Hussain said it is not clear if this budget will pass, when the funds will be available and what projects will be included. He did say it is important to have projects lined up and ready to go if there is to be any hope of receiving funding. Executive Director Deanna Jackson said projects have to be at the minimum, listed on the website and then the GSP to be eligible for grant funding. She advocated getting some kind of land fallowing draft on the TCWD website. Hussain agreed there needs to be a draft document up for review. Director Molly Thurman asked if these projects can be landowner driven or have to be GSA driven. Jackson used the White River flood capture as a start and other projects need to be listed on the GSP for public funding. He said to get any private projects to them by August so they get on the DWR radar. Hussain said to bring even the concept of a project to him. Someone said if they were the governor facing a recall they’d want to get the funds out ASAP.

Jackson said she’s heard choosing a coordinator for the Deer Creek Watershed was very near.

DMS Update

Jackson said she’s working with Four Creeks Engineering and the data management system is close to operational.Conterra

Subsidence

Hussain said there have been groundwater models for all the Tule Basin areas and they don’t all match up. He said DWR uses the C2V Sims model. A gentleman named Bob Anderson who also works for Geosyntec led the committee through updates on models and related a discussion with hydrogeologist Tom Harder. He said it was a productive conversation. There was input that changed things. Not sure what was changed. 

Anderson said the 2019 model has been updated to the 2020 model that had a higher resolution but Land IQ wasn’t used so there are still some differences in unity. Some areas had different evapotranspiration figures. The Tri County pumping rates were dramatically different between the 2019 and the 2020 model. Also changed was the distribution of depth for wells being pumped. The 2020 divided the depth into four zones as opposed to the 2019 two zone model. This helped refine the amount estimated to be pumped above and below the Corcoran Clay layer and that has a big impact on figuring the rate of subsidence.

The model uses force factors – pumping and recharge. The changes of force factors caused some differences between the modeling results. One big change was the rate of subsidence in TCWD. It’s increased in the second model. There is still some data that needs to be run through the grinder to satisfactorily determine results as accurate as can be. One issue was to define is this was truly a model update and if so how. Also how will the sustainable yield be impacted? Anderson said there needs to be a better understanding of the deep and shallow aquifer impacts.

Next Anderson talked about DWR’s C2V Sims model. There is now a fine grid version of this model and only Kern County chose to use C2V Sims as most folks didn’t think it was accurate enough. That led to a hodgepodge of models throughout the Valley.

Anderson said there are many issues to consider in modeling. Boundary constrains of multiple GSP models is one problem. Tying modeling results to yield, allocation and boundary flow management needs to be available. Well fields verses individual wells need to be sorted.

Anderson said trying the C2V Sims model could be another tool in the kit to help support the current modeling to implement the GSP. There are some potential benefits. The latest C2V Sims is now a fine grid upgrade from the older version. Anderson said this model allows for cross boundary flows and other features that improve efficiency and flexibility. He put up some screen shots that showed the comparison and contrast of the C2V Sims and the Harder models. Some of these comparisons show what I would call conflicting data. For instance the direction of the flows above and below the Corcoran clay are moving in different directions. Anderson said this is very rare and will have to be checked with some serious monitoring.

Recently local reporter Lois Henry had a piece in the New York Times, good for her, that covered subsidence in and near the City of Corcoran. It appears the cause of the problem may be broader then first considered. Anderson spoke on elastic and non-elastic aquifers. He said the conclusion for this presentation is the C2V Sims model could help provide more information that will help plan for preventing subsidence and other undesirable results. He pointed out the models won’t solve anything but they will provide some data (as long as it isn’t conflicting) that will help negotiate the least painful remedies to SGMA compliance.

I believe it was Mark Grewal who said for his choice he’d like to see these models continue at least through a wet year. Jackson asked if there was anything else Anderson wanted to say. She thanked him because Tri County is in two different subbasins and the modeling differences need to be reconciled.

Water Accounting

Perhaps Jackson didn’t feel that groundwater modeling was mentally taxing enough on me so she dived into water accounting policy. She said she expects much more water to be brought into the area than sold or transferred out of the area. However, the proposed policy will allow a landowner to credit a water transfer out of the GSA and into and within the Tulare Lake Subbasin or the Tule River Subbasin. But, if I understood correctly you can’t transfer out of the Tulare Lake Subbasin.

Someone asked about a water bank. Can you transfer that water out? It was argued, logically I believe, that the leave behind will benefit the area enough to justify the practice. Everyone on the committee was very much OK with importing water for recharge. Thurman was in favor to start discussions on developing incentives in the policy to bring in new water and not let that be confused with native water. There was much more policy talk before the meeting adjourned.

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TRI-COUNTY WATER AUTHORITY

www.tcwater.org

944 Whitely Ave. Ste. E, Corcoran, CA 93212   Phone: 559/762-7240 DWR# 5-022.12

Tri-County Water Authority is a collaboration of Public Agencies, Water Suppliers, Communities, Cities, County, Environmental Groups, Government Representatives, and a variety of other interested parties. The goal is to identify and implement water management solutions on a regional scale that increase regional self-reliance, reduce conflict, and manage water to concurrently achieve social, environmental, and economic objectives.

Directors & Staff: Cory VanderHam – Chairman, Mark Grewal – Vice Chair, Steve Jackson, Wade Magden. Deanna Jackson – Executive Director, Amer Hussain – consulting engineer.

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