SodaCanyonRoad | What is Happening to Our Most Precious and Irreplaceable Resource: Our Water
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What is Happening to Our Most Precious and Irreplaceable Resource: Our Water


Gary Margadant | Feb 13, 2017 on: Napa Vision 2050

Editor: This interesting read researched and written by Gary Margadant and Elaine de Man describes why we need to think carefully about Napa County's alternative plan for groundwater management. In the next days we will post some of the public comments on the Sustainable Groundwater Management Act alternative submitted by our Board of Supervisors to the California Department of Water Resources. It is critically important that citizens become aware of the stakes involved to our future water supply.


The number of wineries in the Napa Valley has more than doubled over the last twenty years—from about 280 in 1996 to around 570 now--all using free water from the ground. This growth is unsustainable, yet local government and wine industry trade groups continue to fund and market Napa Valley, attracting visitors from around the world at a rate that increasingly overburdens our roads and resources. What we don’t see, however, is what is happening underground to our water supply.

In 2014 Governor Brown signed the Sustainable Groundwater Management Act (SGMA) to address the alarming depletion of regional groundwater. Among other things, this act requires local governments to form a Groundwater Sustainability Agency (GSA) to create and implement a Groundwater Management Plan for water basins that have been designated as medium- or high-priority. The floor of the Napa Valley from Calistoga to Napa, more formally known as the “Napa Valley Sub-Basin,” is considered a medium-priority water basin.

Sustainable Water Management?

Instead of following SGMA’s plan, the Napa County Board of Supervisors opted to take an end-run by submitting an “alternative” plan to the GSA. Napa County claims that the groundwater in the Napa Valley has been sustainably managed for the past 10 years. To support that idea, the County hired consultants Luhdorff and Scalmanini (LSCE) to prepare a report on the state of the Napa Valley Sub-Basin and county’s management of it. The report, entitled Basin Analysis Report, was completed late last year and claims that the Napa Valley Basin has been ‘stable’ for the last 10 years, eliminating the need for a Groundwater Sustainability Agency or the Groundwater Management Plan that would otherwise be required by the state.

Careful examination of the LSCE report determined that there could be catastrophic errors in acting on the conclusion that the Napa Valley Sub-Basin has been adequately managed over the past 10 years. Recommendations by citizens were made to the Board of Supervisors that more study was needed. Nevertheless, this report was accepted, approved, and submitted to the State of California by the Napa County Board of Supervisors.

Factors not considered in this report:

* The report does not consider the impact of the changes in climate that we already are experiencing on groundwater supplies, including the impact of hot days, the effect of drought on groundwater and the diminution of water supplied by the North Bay Aqueduct (NBA).The NBA is a pipeline carrying water from the Sacramento River to Napa Valley and Solano Valley. The NBA water supply is dependent on the Snow Pack in the Sierra Mountains. In a drought, the amount can be reduced to 5% of normal, requiring cities in Napa County to rely only on their limited water reservoirs, Hennessey and Milliken (Napa City), Bell (St Helena), Rector (Yountville, Veterans Home), Kimball (Calistoga).

*Most of the grapes grown in the Napa Valley are grown on the valley floor. These grapes are grown using groundwater extracted from wells drawing on our aquifers.

*The amount of water extracted through these wells is not metered.

*Some well owners are not required to report groundwater extraction at all.

*Some are required to self-report to the county the amount of groundwater extracted.

*Water use estimations are part of a winery use permit, yet the water amount actually used is never verified.

These groundwater extraction reports are not available to the public. The bottom line is that no one really knows how much groundwater is being extracted from our aquifers. If the county is successful in dodging the establishment of a Groundwater Sustainability Agency, business will continue as usual and groundwater extraction will continue to go unmetered and unknown.

An Uncertain Water Budget

Part of the flawed LSCE analysis includes a “water budget”: a determination of how much water flows into the valley through rainfall versus how much water is removed from the valley or captured in ponds and reservoirs before reaching the valley floor for consumption by residents or agricultural irrigation. The chart below, not based on water meters, calculates that there should be a net gain within the aquifer of 6,000 acre ft/yr.

But, the data collected over the last 10 years does not show that to be the case. The aquifer has remained stable, not grown and will not grow in the future.

How can that be? As the LSCE chart indicates, uncertainty in the individual budget components (italicized) of “Upland Runoff” and “SW Outflow and Baseflow,” which represent the greatest amount of water flowing into and out of the aquifer, bear the greatest degree of uncertainty.

As some of these conclusions are based on hypothetical, calculated information, we might conservatively assume they may be off by 2%. And if we take a worst case scenario which is less input AND more outflow than shown we might see that:

Upland Runoff is actually 145,000 minus 2,900 (2%) or 142,100 ac-ft/yr
and, SW Outflow and Baseflow are 176,000 plus 3,520 (2%) or 179,520 ac-ft/yr

If that is the case, we would have an annual change in Subbasin Storage of negative 37,420 ac-ft/yr.

What the LSCE report fails to state is the actual margins of error in the calculations. So the question is, is the 2% margin of error we estimate a risk we are willing to take?
If the answer is yes, it would 1. save the county money by not having to create a new agency (GSA) and 2. avoid more bureaucracy. But we believe the answer is No. Ongoing monitoring of our water supply is paramount to the future of the wine industry and residents of the Napa Valley. Vineyard development of our hillsides and watersheds is rampant with more applications in the pipeline at the County’s Planning Department. No data has been presented to back up the LSCE report assumption that hillside vineyard development will not impact the “upland” flow of water into the subbasin. Although data may be available from wells that are already located in strategic areas, the groundwater levels are subject to the impact of hillside development. If those wells are not identified and we don’t have access to the data, we have no way of knowing what the negative impacts of the conversion of hillside forests to vineyards might be.

The consequences of the County’s current course of action are too high: lowered groundwater levels, degraded water quality, land subsidence, and saltwater intrusion into groundwater. These are the same undesirable results that SGMA was designed to curtail! It is imperative that we take the long view in this time of global climate change and inform the State of California of the serious errors in the County’s report and the dire consequences to our Napa Valley if we do not establish accurate groundwater data by metering. The fate of our water supply is in the State’s hands now.

Please use this link to comment to the State of California Department of Water Resources by February 15, 2017.

Talking points:

1. Although the County report prepared by Luhdorff and Scalmanini claims the Napa Valley Sub-Basin has been adequately managed over the past 10 years, there appear to be serious errors that could be catastrophic to the county’s water supply. More study is needed before such an alternative plan is granted.

2. The report does not take into consideration the impact of the development of the hillsides on the groundwater in the subbasin.

3. Until we have more available hard data on groundwater levels, water quality, land subsidence, and saltwater intrusion into groundwater wells, we cannot make responsible decisions on groundwater management. Recommend that use permit holders be required to monitor wells and to submit data to the county.

4. Any abuse of water use, when metered and identified, must be corrected.

Please also contact our Board of Supervisors and encourage them to support and enact this crucial monitoring of groundwater to fully understand the impact of hillside planting and wells on our groundwater supply.

From the Water Balance charts in the NV Basin Plan.