Hamera Shabbir at City Council Meeting

PHS AP student Hamera Shabbir, right, listens to the groundwater management program presentation during the City Council meeting on Tuesday, Oct. 1. Hamera asked a couple of questions that triggered a more in-depth discussion of land subsidence, which scientists believe is caused by groundwater pumping.

terson Irrigator

As required by legislation signed into law during the drought, the City Council on Oct. 1 accepted a Groundwater Sustainability Plan (GSP) presented by staff, and set a public hearing to adopt the plan, called the Northern and Central Delta-Mendota Region Groundwater Sustainability Plan, during its meeting on Dec. 17.

The new law, called the Sustainable Groundwater Management Act of 2014 (SGMA), calls for a statewide plan to manage groundwater sustainably, and requires, for the first time ever, that local jurisdictions dependent on a water resource, such as the Delta Mendota sub-basin, work together to ensure the sustainability of that resource.

In creating the plan, a nearly 2,000-page document covering every aspect of managing local groundwater, the city worked cooperatively with the Aliso Water District GSP Group, Farmers Water District GSP Group, Fresno County GSP Group, Grassland GSP Group, Northern & Central Delta-Mendota Region GSP Group, and San Joaquin River Exchange Contractors GSP Group. A total of six GSPs are being developed for the Delta Mendota sub-basin by eight groups, called Groundwater Sustainability Agencies (GSAs). The City of Patterson is one of the these. The others are Central Delta-Mendota, DM-II, Northwestern Delta-Mendota, Oro Loma Water District, Patterson Irrigation District, West Stanislaus Irrigation District and Widren Water District.

SGMA requires that a GSP be developed that achieves groundwater sustainability in the Delta Mendota sub-basin, one of 21 water resources that the Department of Water Resources (DWR) considers “critically overdrafted,” by 2040. The plan must be adopted and submitted to the DWR by January 31.

A number of public workshops were held during the creation of the GSP, and although not required, the city voluntarily included a public comment period, which ended on Oct. 11.

GSPs are required to cover a 20-year implementation period, as well as a 50-year planning period. In her presentation, Dr. Leslie Dumas, Senior Technical Practice Leader with Sacramento-based Woodard & Curran, pointed out, extends to the year 2070.

Dumas and her team used a conceptual model to study how water comes into, and moves within, layers of the earth in the sub-basin. Thirty-five wells will be monitored for changes in groundwater; both levels and quality. Two wells will be monitored for interconnected surface water, and land subsidence will be measured at 31 sites.

Land subsidence

Land subsidence, or sinking, is believed to be related to groundwater pumping, Dumas said. Elevation benchmarks have been placed along Delta Mendota Canal and other locations, Dumas said, “especially up here in the Patterson area, because there are some indications that this area could be more sensitive to subsidence, and we want to get information as soon as we can to confirm that.”

Water quality

SGMA requires GSAs to manage the quality of the groundwater supply, among other things. Naturally-occurring contaminants, such as chromium 6 and arsenic, exist in the sub-basin. The GSP must acknowledge that such contaminants exist, Dumas said, but it is not within the GSA’s realm to control them. Of local concern are total dissolved solids (TDS), nitrates and boron, she said.

Interconnected surface water

This aspect of the GSP focuses on river flows and stages, and the impacts changes in flows have on wildlife habitat.

“We should be ok”

Based on the studies, assuming the GSP is adopted and implemented, Dumas said, “we should be OK – that’s an important takeaway.”

When Councilmember Cynthia Homen expressed concerned about wildlife along San Joaquin River, Dumas said that the section of the GSP covering interconnected surface water addresses the relationship between groundwater extractions and surface water bodies, such as the river. But, because several members of the GSA hold permits to divert water from the San Joaquin river, Dumas said, it’s “very important that the flows are maintained in the river, because that’s what allows them to divert; it becomes a win-win.”

Councilmember Dominic Farinha asked what happens to those entities that are are actually doing the right thing, but they’re immediately adjacent to other GSAs that may not be as honest.

Dr. Dumas explained that the entities involved in the GSA are currently coming up with implementation guidelines, and pointed out that the bulk of the work to date has been geared toward creating a GSP by the deadline. “Everybody’s been so hyper-focused on getting these plans done in the timeframe that we’ve had, there really isn’t a lot of time for coordination. Those concerns are currently being discussed, she added. She also said that the group has been meeting with groups from neighboring sub-basins

Mayor Deborah Novelli asked about assistance from the federal government; Dumas pointed out that the DWR has an established relationship with the Bureau of Reclamation, who has recently shown interest in participating in the GSP process.

Good question

PHS senior Hamera Shabbir, attending the council meeting with a group of AP government students, asked if groundwater levels in the Delta Mendota lower aquifer, which reached 95 percent of historic low during the drought, would have to reach 95% of historic low, or would have to come within 5% of that for there to be any concern.

Dr. Dumas, clearly pleased with the question, explained that the Delta Mendota sub-basin 

is considered critically overdrafted because of land subsidence. Scientists believe that most land subsidence occurs due to pumping of the lower aquifer, which lies beneath a layer of Corcoran clay, which is under the upper aquifer.Scientists believe that most land subsidence occurs due to pumping of the lower aquifer, which lies beneath a layer of Corcoran clay, which is under the upper aquifer.

There was “a lot of land subsidence during the last drought.,” Dumas said. Using the example of a mattress with too many people on it, Dumas explained that when groundwater, which separates layers of clay and soil under the earth, is pumped out and removed, the land subsides, or sinks, as the spaces where the water was held collapse. Once that has happened, she said, “you can’t put water back in; there’s no space there.”

To arrive at the percentage, which Dumas admitted was “an estimate on our part,” the group took levels measured in 2015, the worst during the most recent drought, at which point “we know we have problems,” and determined that water levels within 95 percent of that level would trigger further measures. That number is subject to change, she noted, as conditions are observed in real time.

With the heavy rains in 2017, she said, groundwater levels “came shooting back up,” and land subsidence began to slow down.

Hamera also asked if the plan included private wells. Dumas explained that all well owners are required to manage them, as well. However, specific wells have been selected for monitoring, most of which belonged to larger water users, such as the City of Patterson.

The Public Draft Groundwater Sustainability Plan is available online at deltamendota.org.

Weed, mistletoe abatement liens

The council also approved a resolution to place liens on properties whose owners have outstanding weed or mistletoe abatement charges with the city. Such charges occur when property owners do not remove weeds and other debris from their property or mistletoe from their trees, and the city pays an outside contractor to do the work. The owner is then billed for the cleanup. If unpaid, the city can place a lien the property for the amount due. A total of nine property owners have outstanding charges of $6,265.25, which will be placed as liens against their properties. Generally speaking, such liens must be satisfied when a property is sold.

Parks, Recreation & Beautification Commission

The following were appointed or reappointed to the Parks, Recreation & Beautification Commission: Alexandria Tyler, May 2019 - May, 2021; (reappointment) Karina Contreras, May 2019 - May 2021; Richard Reiller, May 2019 - May, 2021; Paula Obledo, May 2018 - May 2020. were all appointed to the commission.

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