Sep 1 2014
In the New Testament of the Bible, Christ turns water into wine, and
apparently Deborah Brennan Sullivan is an advocate of doing the same thing.
The front page story of the Monday, September 1, 2014 UT San Diego goes into
great detail about why growing grapes and making wine is a serious water
saving alternative to growing avocados or other thirsty crops.
Since avocados are measured by the pound and wine is usually measured in
liters, comparing them is a little dicey, but for the purpose of the blog,
let’s say a pound of avocados is equal to a liter of wine. It is true that
avocados, a very thirsty fruit, take a lot of water. A pound of them has a
water footprint of 582 liters of water (154 gallons) While a liter of wine takes much
less, only 120 liters.
For those who don’t think about water footprints, those numbers may seem
high. The water embedded in a pound of avocados is not just the irrigation
water it takes to maintain a healthy tree, it is all of the infrastructure
needed to bring a pound of avocados from that tree to the mound of avocados
in a super market where the shopper can select just the right ones (not too
hard and not too soft). For wine, it is essentially the same process (grapes
to bottles of wine on the grocery store shelves).
Figuring how many bottles of wine there are to an acre depends upon the
yield, but it is somewhere between two and ten tons of grapes per acre, or
between 1440 bottles and 7200 bottles. Let’s use six tons for an average
yield, or 4,320 bottles of wine. So, how much water is used per acre?
Because we are used to figures in gallons, first we need to convert 120
liters to gallons (for one bottle). That is 31.7 gallons per bottle. And
multiplying by 4,320 bottles per acre, we get 136,947 gallons of water
needed per acre.
According to Ms. Brennan’s piece, in 2012 there were 303,983 acres being
cultivated for agricultural use. We know there will always be diversity in
crops, but let’s assume that all of that acreage is devoted to grapes and
wine production, which the article seems to recommend. When we multiply one
hundred thirty seven thousand gallons per acre time three hundred four
thousand acres. The result is 41.4 trillion gallons (with a T), or in acre
feet, that is 127,184 A-F.
Again using Ms. Brennan’s numbers for Agricultural Water Usage for 2013 in
San Diego County: 50,503 acre-feet was used. An important assumption is
necessary at this point. Let’s assume all of the grapes harvested are
processed into wine within the county, just as the article indicates, so the
water footprint is a San Diego water footprint.
Even if we drop the grapes yield per acre down to two tons from the average
six tons used above, we see the calculated 304 thousand acres require one
third of the total above or 42,394 acre-feet. The University of California
Cooperative Extension Publication for Wine Grapes is a study in the
Temecula area in 2000. At that time, and costs are higher now, it took
between four and seven and a half tons per acre to profitably grow grapes.
So the assumption of six tons per acre used in the example is close.
The amount of water used for crops in San Diego County is out of proportion
to the economic effect. With a 2012 GDP of $177.4 billion, the contribution
is less than one percent, or $1.74 billion, again using Ms. Brennan’s
numbers. In the article, unless there is a baseline, that $1.74
billion looks huge, but it isn’t. In the pie chart, it is a sliver that is
less than the arts and entertainment or educational services.
Can we say if all of the 304 thousand acres of agricultural land was planted
to grapes there would be a savings in water imported into the county?
Absolutely not, in fact the water use could nearly triple. When will reason
prevail that attempting to make San Diego an agricultural mecca is out of
the question? We live in a desert. However romantic the idea, growing
grapes does not transcend reason. It is not sustainable to consume ten
percent or more of the water imported for agricultural uses, even to grow grapes.
By Milt Burgess • Blog • 0 • Tags: augmentation, California Aqueduct, Colorado River, conservation, dry centuries, El Nino, La Nina, MWD, precipitation, purple pipe, SDCWA, State Water Project, water districts, water rate hike, water Storage, wet centuries