Nuts getting a bad rap for sinking the California Aqueduct

February 6, 2020
by Lois Henry
Lois Henry

BY THE NUMBERS

The recent state report about subsidence along the California Aqueduct looked at changing crop patterns in the San Joaquin Valley.

The report, released Dec. 31 by the Department of Water Resources, is supplemental to a study done last March. The March 2019 study found that subsidence beneath the Aqueduct caused by deep groundwater pumping had reduced its capacity by 20 percent.

The Dec. 31 supplemental report predicted that if current pumping levels continue, the state would not be able to deliver historical maximum supplies in as few as three years.

The report also looked at top-value crops over an extended period of time county by county and estimated the water use of those crops.

Merced County

Between 2004 and 2015, estimated water use for Merced’s top crops increased by about 230,000 acre feet per year, according to the report.
Here’s how the top crops changed over time.

2004 (based on valuation and in descending order of harvested acres)
Almonds
Alfalfa
Corn for silage
Cotton
Pasture
Tomatoes for processing
Sweet potatoes
Nursery products
Acres of top crops: 408,000 of 587,000 total farmed acres
Estimated water use for top crops: Nearly 1.5 million acre feet a year, or 95% of total ag water use.

2015
Corn for silage
Almonds
Other silage
Alfalfa
Tomatoes for processing
Pasture
Sweet potatoes
Wine grapes
Cotton
Tomatoes for market
Acres of top crops: 499,000 of 652,000 total farmed acres.
Estimated water use for top crops: 1.7 million acre feet a year, or 82% of total ag water use.

Fresno County

Between 1994 and 2016 estimated water usage on Fresno’s top crops decreased by about 195,000 acre feet per year, according to the report.

1994
Cotton for lint
Grapes
Tomatoes for processing
Almonds
Cotton
Oranges
Lettuce
Garlic
Nectarines
Tomatoes for market
Acres of top crops: 814,000 of approximately 1.2 million total farmed acres
Estimated water use for top crops: Nearly 2.2 million acre feet a year

2016
Almonds
Grapes
Pistachios
Tomatoes for processing
Cotton
Oranges
Garlic
Peaches
Tomatoes for market
Acres of top crops: 697,000 of 991,000 total farmed acres.
Estimated water use for top crops: Nearly 2 million acre feet a year, 95% of all ag water use.

Kings County

Between 1996 and 2015, estimated water use on Kings’ top crops decreased by about 162,000 acre feet per year, according to the report.

1996
Cotton, Acala
Cotton, Pima
Alfalfa for hay
Tomatoes for processing
Walnuts
Grapes
Peaches
Alfalfa, other
Tomatoes for market
Acres of top crops: 308,000 of approximately 547,000 total farmed acres
Estimated water use on top crops: 1 million acre feet a year

2015
Cotton, Pima
Corn silage
Alfalfa for hay
Tomatoes for processing
Almonds
Walnuts
Alfalfa for stubble
Grapes
Cotton, Acala
Alfalfa
Acres of top crops:  257,000 of approximately 439,000  total farmed acres
Estimated water us on top crops: 883,000 acre feet a year.

Kern County

Between 1998 and  2015, estimated water use on Kern’s top crops increased by about 534,000 acre feet per year, according to report.

1998
Cotton
Alfalfa for hay
Grapes
Almonds
Wheat
Citrus
Pistachios
Potatoes
Tomatoes for processing
Onions
Acres of top crops: 664,000 of 868,500 total farmed acres
Estimated water use on top crops: 2.1 million acre feet a year.

2015
Almonds
Pistachios
Grapes
Alfalfa
Silage
Citrus
Cotton
Tomatoes for processing
Pomegranates
Cherries
Garlic
Acres of top crops: 750,000 of approximately 886,000 farmed acres
Estimated water use on top crops: Nearly 2.5 million acre feet a year.

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State water officials are blaming almond and pistachio orchards for sinking the California Aqueduct before all the evidence is in, according to one western Kern County water district manager.

“They need to do more homework,” said Jason Gianquinto, General Manager of the Semitropic Water Storage District. “It’s easy to say, ‘Hey, this area is subsiding and, by the way, there’s ag here.’ But it’s not taking into account where the water for that ag is coming from.

“It’s a knee jerk reaction.”

Gianquinto referred to a report issued by the Department of Water Resources on Dec. 31 that put the blame for several areas of Aqueduct subsidence on heavy groundwater pumping in order to sustain a massive increase in orchard and vineyard plantings.

In Lost Hills, which is covered by the western fringes of Semitropic, a section of the Aqueduct has dropped up to four feet, according to the report.

“Subsidence around Lost Hills is a valid concern,” Gianquinto said. “But there isn’t a lot of groundwater production out there. It’s too salty. Most of the crops in that area rely on surface water.”

Semitropic does pump groundwater. In fact, it pumps so much groundwater it’s overdrafting by  between 165,000 and 256,000 acre feet a year, according to its groundwater sustainability plan.

But, in regards to subsidence on the Aqueduct, where Semitropic farmers pump is potentially more important than how much they pump, according to Gianquinto.

Very little groundwater pumping is done west of the Buttonwillow Ridge, a geologic barrier which runs along the east side of the Aqueduct, he said. Most of Semitropic’s growers pump east of that ridge.

“(The state) need to look at the geology and see if there is much, if any, groundwater communication east to west. And which zones are collapsing? They looked a lot at crop conversion, but they need to do a deeper dive on the geology before they start pointing fingers.”

It appears, however, that finger pointing has already commenced.

Days before the Dec. 31 report was released, DWR fired off comment letters to several Groundwater Sustainability Agencies with borders along the Aqueduct letting them know the state considers subsidence a top issue.

In Dec. 26 comments sent to the Kern Groundwater Authority, DWR wrote: “GSP (groundwater sustainability plan) Section 3.1.3  Undesirable Results for Land Subsidence, contains the following sentence: ‘While it is generally acknowledged that subsidence exists within the Subbasin, there are generally no significant impacts to infrastructure within the Subbasin.’ We disagree with this conclusion, as subsidence has reduced the flow capacity of the Aqueduct by 19% near Highway 46.”

The state letter also warns KGA not to try and pin responsibility for subsidence on oil production: “GSP states that subsidence associated with oil and gas activities may also occur within the Subbasin. In fact, the March 2019 report finds that oil extraction from the Lost Hill Oilfields did not have a significant contribution along the Aqueduct.”

The same day DWR sent that letter, similar letters were sent to Westlands Water District and groundwater sustainability agencies in the Tulare Lake Subbasin and the Northern and Central Delta-Mendota regions.

The worst area of subsidence on the Aqueduct appears to be in the southern portion of Westlands in western Fresno County.

That section of the Aqueduct, known as Pool 20, has already sunk up to six feet.

DWR wrote of Westlands’ groundwater sustainability plan: “The GSP assumes that ‘residual subsidence’ of 0.1 foot per year will be acceptable on the Aqueduct. We are concerned that if this rate of subsidence continues through 2040 and possibly thereafter, it will further adversely impact the Aqueduct’s conveyance capacity and operational flexibility.”

Calls to Westland’s General Manager Tom Birmingham were not returned.

Groundwater sustainability agencies have until Jan. 31 to revamp their plans and submit them to DWR for approval.


Conversion along the Aqueduct to permanent crops from row crops (in red) in Kings County 1991-2014

 


Conversion along the Aqueduct to permanent crops from row crops (in red) in Fresno County 1986-2014


Conversion along the Aqueduct to permanent crops from row crops (in red) in Merced County 1995-2014

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