Basin sustainability criteria discussed at TAC

Committee questions use of Navy funds for subsidence research

Basin sustainability criteria discussed at TACBy BRIAN COSNER

News Review Staff Writer

What is sustainability when it comes to groundwater resources? The Indian Wells Valley Groundwater Authority’s Technical Advisory Committee spent part of its meeting last week discussing the sustainability criteria as required by the Sustainable Groundwater Management Act.

“There’s a misconception in many basins that the sustainable management criteria are about how much pumping you can do in a particular year,” said Anthony Brown, TAC member and consulting hydrologist for Mojave Pistachio. “SGMA is about undesirable results and about establishing minimum thresholds and measurable objectives for water levels primarily.”

Discussions at the Authority level have gravitated toward the idea that any pumping over 7,650 acre-feet per year – our estimated natural recharge – would need to be offset by an augmented water supply, whether it’s imported, recycled or desalinated water or some other alternative.

“If you can manage your basin and hit those measurable objectives and stay within those minimum thresholds, you may be able to pump the basin for much more than what you thought might be the safe yield,” said Brown. “So it’s not about targeting some number in terms of acre-feet per year. It’s about targeting those thresholds.”

Jean Moran of Stetson Engineers (the water resources management firm for the Authority) verified Brown’s explanation. But Don Decker, the TAC’s private well owner representative, said that declining water levels and our natural recharge are “intimately connected” and that pumping restrictions would be the same.

“We’re already repairing shallow wells, so it’s not like it’s a future thing that’s going to happen,” said Decker. “It’s been happening and it will continue.”

Brown agreed to an extent, but reiterated that “it’s the levels you set with SGMA, not pumping rate. The outcome of those water levels will be your pumping rate eventually. It will be some number close to what might be perceived as the safe yield.”

“This is a very important point,” said Tim Parker, the IWV Water District’s consulting hydrogeologist. “We’ve got a model and it’s based on our best guess to safe yield … and we debated the model as to what the actual safe yield is. And it was anywhere from 2,000 acre-feet per year to 11,000. And if then you look at the literature it could be up to 30,000.”

He said the realistic range was probably 4,000 to 11,000 acre-feet per year, but again it would come down to the rate of decline to our groundwater table.

Other sustainable management criteria include reduction of groundwater storage, seawater intrusion, degraded water quality, land subsidence and depletion of interconnected surface water – most of which are non-issues for our valley.

According to the Department of Water Resources, all criteria need to be considered to some extent even if only to eliminate them from further analysis.

TAC members agreed that degrading groundwater quality would probably need to be addressed, but questioned whether subsidence was a real problem.

Steve Bacon of the Desert Research Institute gave a brief presentation on land subsidence – gradual or sudden sinking of the earth’s surface – caused by tectonic activity and groundwater pumping.

According to Bacon, the portions of our basin composed of fine-grained material are prone to compression as a result of groundwater pumping, which can result in measurable land subsidence. Areas of our basin are experiencing such subsidence, but only at the rate of tenths of an inch per year.

Bacon added that determining how much of the subsidence is being caused by tectonic activity, groundwater pumping or both can be a complex issue.

“Are we making a mountain out of a molehill here?” asked Eddie Teasdale, TAC vice chair and representative of Meadowbrook Dairy. “Maybe there are certain areas we need to focus on, but everywhere else I don’t see any ‘significant and unreasonable’ issues.”

Decker said there is photographic evidence of serious subsidence issues stemming back to early 20th- century agricultural pumping in the valley. But beyond photographs that would need to be found, he said, there’s no hard evidence for it.

Brown said he doesn’t think subsidence is in issue here in relative terms.

“In the Central Valley we’re dealing with levels of subsidence that are 100 times what it is here,” he said. “And they don’t even think it’s significant, though that might be questionable.”

“We’re not seeing subsidence to be a controlling factor in developing a sustainability plan right now,” said Water Resource Manager Steve Johnson. “Monitoring going forward I think is something we really want to look at and get input on. We certainly want to get input from the Navy on that.”

Despite the TAC’s consensus on the topic, Navy Representative Stephan Bork announced that China Lake would be using National Defense Authorization Act funds to look more into subsidence.

“Has the Navy made the final decision that they want to move subsidence above drilling some of the wells that we proposed?” asked TAC Member Scott O’Neil.

“Yes, we actually had a very short time frame to make a decision on what to apply for for funding,” said Bork.

NAWS China Lake Community Planning Liaison John Kersey added that the group had three days to put in for a project or they would have missed the deadline.

“As far as I’m concerned, the Navy has had nine months to really work on this, so I would like to have a conversation with the Navy on this,” said O’Neil. “I’m saying there’s other ways to challenge the deadline.”

The IWV Groundwater Authority will next meet on Thursday, May 16, 11 a.m. at City Hall.

Brown will also give a brackish water presentation to the IWV?Water District during it’s regular meeting on Monday, May 13 at the district office, 500 W. Ridgecrest Blvd.

Pictured: Technical Advisory Committee Chair Adam Bingham (left) and Mojave Pistachio’s consulting hydrologist Anthony Brown (sitting in for Wade Major) at last week’s TAC meeting — Photo by Laura Austin

Story First Published: 2019-05-10