Napa Valley’s annual groundwater checkup yielded the verdict that the water table in the world-famous grapegrowing region is “generally very shallow” and that the basin is “full.”
There are problem spots, such as the Petra Drive area northeast of the city of Napa that the county is studying. The Coombsville area still faces groundwater challenges, though the county sees the situation as having stabilized.
But overall, the county’s 2016 groundwater report by consultating engineers Luhdorff & Scalmanini to the Napa County Board of Supervisors last week emphasized the positive, especially when it came to the valley floor.
“I think the message I really want to challenge everyone with is, ‘how do we share this with our residents?’” Supervisor Alfredo Pedroza said.
Michelle Benvenuto of Winegrowers of Napa County agreed.
“This is good news, quality and quantity,” Benvenuto told supervisors. “We have to let Napa know what’s going on.”
The 2016 data was gathered before the latest rainy season hit, bringing Napa State Hospital more than 43 inches of rain, the third wettest total on record since 1892. Some stations on the valley floor have reported receiving more than 50 inches of rain since Oct. 1.
As a result of all this rain, next year’s groundwater report should look even better, county Natural Resources Conservation Manager Patrick Lowe told the Board.
News is hardly good everywhere in the state. In the San Joaquin Valley, where wells have been overused for decades, some areas have seen recent subsidence rates as much as two feet annually.
As a result, California is requiring communities to take steps to oversee groundwater supplies.
Napa County is trying to convince the state that it has managed the Napa Valley groundwater basin in a sustainable way over a decade. Otherwise, it must form a groundwater sustainability agency by July and this agency must create a groundwater sustainability plan by 2022.
The county is counting on its 1,000-page-plus basin analysis report to sway the state. But the state Department of Water Resources has received various submissions from people and agencies who are urging the agency to reject the county’s request.
In response, the Napa County submitted a 76-page letter to the Department of Water Resources addressing the various criticisms.
At the heart of this debate is whether Napa County has avoided what the state calls “undesirable results.” These results are chronic lowering of groundwater levels, significant groundwater storage reduction, significant seawater intrusion, significant degraded water quality, significant subsidence and significant depletions of groundwater connections with streams and rivers.
For example, the California Department of Fish and Wildlife is concerned that groundwater use near the Napa River affects the amount of groundwater that can seep into the Napa River and increase its summer flow to help fish, such as the steelhead trout.
“In the Napa River, the late spring through fall season is a critical period in the life of steelhead,” the letter said. “Insufficient flow during this period can delay or preclude migration patterns and decrease rearing habitat.”
Napa County responded that diminished groundwater flows into the Napa River have happened at times since the 1930s during dry years. The two parties disagreed over whether the condition is worsening.
The Union of Concerned Scientists is concerned that land subsidence may be occurring. But the county responded that the Union of Concerned Scientists has misinterpreted the data.
Now all the county can do is wait to see if the state will agree that it is already doing a good job managing its groundwater. It expects a decision within a few months.