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The real facts on Napa's aquifer

The real facts on Napa's aquifer


On April 22, Chris Malan weighed in with her support of Measure C, using the argument that "the science is solid and long settled..." ("Science supports an imperative yes vote for Measure C").

I am writing not about the pros or cons of Measure C, but about the repeated citing of "facts" that are anything but factual.

Malan writes about both quality and quantity of water, and I am going to focus on Malan's comments about the quantity of water in our well-studied aquifer, the one that lies under the floor of the Napa Valley from Calistoga to just south of the town of Napa.

The California Deptartment of Water Resources identifies it as the "Napa Valley Subbasin" and has determined that it is a "Medium Priority" aquifer in their classification system, which uses, among other factors, population, total number of wells and total irrigated acreage. Malan's main allegations about the state of the aquifer are:

1) the Sub-basin has been determined to be "in moderate depletion" [determined by whom is not revealed.]

2) the aquifer is "unable to recharge itself sufficiently over time;"

3) that is because of "60 percent of groundwater demand by vineyards;"

4) that groundwater is polluted, and that there is salt water intrusion, land subsidence and surface water depletion of streams.

5) For all the above reasons, Napa County is "required to develop a Groundwater Sustainability Agency and a Groundwater Sustainability Plan, which could regulate triggers to stop pumping if over drafting is causing harm."

6) "Napa County chose to sidestep this science [sic] and represents to [the state] that a groundwater monitoring program should suffice."

7) Therefore, "Napa County's groundwater is in peril."

As called for in the 2008 General Plan, the County in 2009 embarked on a thorough and well-designed program to understand the aquifer of the Napa Valley Subbasin, with the aid of consulting engineers LSCE. The culmination of all that work done to date, accomplished with the cooperation of countless landowners, indicates without doubt that:

1) The aquifer is in equilibrium with demand;

2) Taken as a whole, groundwater levels do respond to rainfall patterns, so that in dry years, groundwater levels drop, but with the return of normal or above-normal rainfall, groundwater levels recover—almost immediately.

3) Much of the aquifer's groundwater feeds the flow of the Napa River—it is a "gaining stream" over much its length during much of the year.

4) There is no evidence of widespread pollution of groundwater, though there are a few very localized areas of elevated nitrate levels. There is a natural freshwater/saltwater interface but no evidence of increasing salt water intrusion or ground subsidence in the Subbasin. The county has embarked on a program to study surface-groundwater interactions at five sites and is looking to install several additional study wells as funding permits.

5) To comply with the Sustainable Groundwater Management Act, Napa County is required to analyze the condition and trends of the Subbasin's groundwater resources, which it has done and has submitted for approval to the state Department of Water Resources. The Board of Supervisors chose proactively to submit an Alternative Plan to meet the following criterion: “An analysis of basin conditions that demonstrates that the basin has operated within its sustainable yield over a period of at least 10 years." [Water Code 10733.6.b(3)

6) The Supervisors aren't sidestepping anything—they are relying on information painstakingly collected and analyzed in some cases for decades. They chose this path because the information and analysis to write the Alternative Plan was available to show sustainability— and the state required that these Alternative Plans be submitted by Jan. 1, 2017 (Napa County's was submitted on Dec. 16, 2016); the deadline for a Groundwater Sustainability Plan (GSP) would otherwise be Jan. 31, 2022. The standards of analysis that need to be met and the level of scrutiny by the Department of Water Resources are similar for an Alternative Plan (functionally equivalent GSP) and a GSP.

7) For all of the above reasons, I believe our common resource of the aquifer of the Napa Valley Subbasin is in good condition, is being monitored diligently and that additional information is being gathered to improve our understanding and management of this vital resource.

But don't take my word for it; the entire Alternative Plan and the most recent Annual Report are available at There, you will find the Basin Analysis Report for the Napa Valley Subbasin and the Annual Reports, the most recent of which was presented in February 2018 for the 2017 Water Year.

David Graves


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