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 Agricultural production and food manufacturing account for a
third of water usage in the U.S. Water use fluctuates with
weather patterns but is also affected by shifts in production
technology, supply-chain linkages, and domestic and foreign
consumer demand.
A comprehensive University of Illinois study looked at water
withdrawals in U.S. agriculture and food production from 1995 to
2010. The main trend was a decline in water use, driven by a
combination of factors.
“Overall, the use of water for irrigation decreased by 8.3% over
this period,” says Sandy Dall’erba, regional economist at U of I
and co-author on the study.
“However, one needs to identify the drivers of water use by crop
as they differ from one commodity to the next, so water-saving
strategies for one crop may not be relevant for another one,”
Dall’erba explains. “For instance, water use in cereal grains,
fruits, and vegetables is mostly driven by the efficiency of the
irrigation system, domestic per-capita income, and sales to the
food processing industry. If irrigation is more efficient, water
demand decreases. When demand for fruits and vegetables
decreased in 2005-2010 during the financial crisis, so did
demand for water.”
Oilseed crops, on the other hand, have experienced a 98%
increase in water demand over the period. The change is
primarily driven by international supply-chain linkages. It
means foreign companies, mostly in China, have purchased large
amount of U.S. oilseed crops for further processing.
“There has also been a shift in consumer demand from red meat to
white meat in the U.S. People consume less beef and more
chicken, which require 3.5 times less water per pound of
production. Those trends in consumption and taste have helped
the U.S. reduce water use for livestock by 14%,” Dall’erba says.
Dall’erba and co-author Andre Avelino performed a structural
decomposition analysis, looking at 18 factors that drive U.S.
water withdrawals across eight crops, six livestock categories,
and 11 food manufacturing industries.
Based on data from Exiobase, a global supply-chain database,
their analysis included water that’s embedded into the
production at all stages of the domestic and international
supply chain, from crops and livestock to processed food
production – highlighting the interconnectedness of global
agribusiness.
For example, crops produced in the U.S. may rely on fertilizers
produced in a different country. Similarly, soybeans produced in
the U.S. could be used for food processing in China, or to feed
livestock in Europe.
The current U.S.-China trade war is likely to affect these
supply-chain linkages, as Chinese import of oilseeds shifts to
South America and Europe. The U.S. exported less soybean and
pork to China over the last two years; therefore, less water was
embedded into those exports. However, the next few years under a
new U.S. administration may see an improvement in these
relationships, Dall’erba notes.
The COVID-19 pandemic is also likely affecting
water usage. Unemployment and economic crises have always
impacted consumer demand, and international trade has sharply
declined since the pandemic began. The 2008 recession resulted
in decreased water usage and similar effects are expected in the
current crisis, Dall’erba states.
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Traditionally, scientists measuring the amount of water associated
with production and the supply chain rely on a worldwide data set
called the Water Footprint Network (WFN), which is based on a crop
water-use model. However, Dall’erba and Avelino used data from the
U.S. Geological Survey (USGS), which are based on observations
rather than physical models.
“With the USGS data we find a decrease in the amount of water used,
while the WFN data indicated a small increase. The difference is not
large, but it's still a big deal, because you would find the wrong
trend and reach misleading conclusions if you use the wrong data
set,” Dall’erba explains.
“This is important information for researchers. If you’re in a
situation where you have access to data based on observations rather
than crop models, you should use those official data, especially
because water saving policies are based on this dataset,” he notes.
The questions addressed in this research are extremely relevant for
any country that is heavy on agricultural production, Dall’erba
says. “Namely, how can we feed the 10 billion people we expect to be
at the global level by 2080, considering that we cannot necessarily
expand the amount of land that's going to be used? And, given
climate change, there is quite a lot of uncertainty with respect to
the availability of water needed to grow crops and feed livestock in
the years to come.”
Water management strategies may include farm-level efforts such as
increasing efficiency of the irrigation system, switching crops, and
growing genetically modified crops.
Other measures may include policies aimed at affecting consumer
behavior such as increasing taxes on water-intensive products and
supporting ecolabeling, Dall’erba suggests.
Ecolabeling would require food manufacturing companies to report the
amounts of water, carbon dioxide emissions, and labor associated
with production. That could help consumers make informed choices and
potentially shift consumption to less water-intensive products, he
concludes.
The article, “What Factors Drive the Changes in Water Withdrawals in
the U.S. Agriculture and Food Manufacturing Industries between 1995
and 2010?” is published in Environmental Science and Technology. [doi.org/10.1021/acs.est.9b07071]
Authors are Sandy Dall’erba, Department of Agricultural and Consumer
Economics, College of Agricultural, Consumer and Environmental
Sciences, University of Illinois, and Andre Avelino, National
Renewable Energy Laboratory.
The research was funded by a United States Department of Agriculture
hatch grant.
[Source: Sandy Dall’erba
News writer: Marianne Stein]
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