(John Kemp is a Reuters columnist. The views expressed are his
By John Kemp
LONDON Feb 10 Water supplies across the western
and southwestern United States are becoming severely strained as
more people move into areas with limited rainfall and shrinking
Since the turn of the century, the 15 states that the
federal government includes in its Pacific, Mountain and West
South Central census divisions have seen their population rise
by almost 17 million.
These three census divisions accounted for half the total
population growth in the United States between 2000 and 2013.
The western and southwestern divisions include most of the
fastest-growing urban areas in the country, according to the
U.S. Census Bureau.
Living without water chartbook:
Population in the western and southwestern divisions grew
twice as fast (1.3 percent a year) as the rest of the country
(0.7 percent). Nevada (2.5 percent), Utah (2.0 percent), Arizona
(1.9 percent), Texas (1.8 percent) and Colorado (1.5 percent)
had some of the fastest compound annual growth rates.
But the west and southwest are also the driest regions in
the country. Most areas receive less than 15 inches (38 cm) of
rain per year, and in some cases less than 10. Rainfall is less
than half that in the rest of the country. In effect, population
is migrating to parts of the country that lack the water
resources to support the increase.
Water has long been the most valuable and fought-over
commodity in the west.
By far the most important source in the region is the
Colorado River. Nearly 40 million people in the basin states of
Arizona, California, Nevada, Colorado, New Mexico, Utah and
Wyoming rely on the river and its tributaries for some or all of
their supply, according to the U.S. Bureau of Reclamation, the
federal government's water management agency.
Use of Colorado water is apportioned among the seven basin
states according to a complex set of interstate compacts,
federal laws and Supreme Court decisions collectively known as
the "Law of the River".
The Law of the River sets out how much water each state can
divert for its own use to supply homes, businesses and farms.
But as regional demands for irrigation and municipal water
supplies increase in line with economic development, pressures
on the water supply are intensifying.
To make matters worse, much of the region is suffering a
long-term drought, with below-average rainfall since 1999. That
has sharply curtailed the volume of water in the Colorado and
other rivers, and trapped behind the region's giant dams.
Between 2010 and 2012, the Bureau of Reclamation and basin
states conducted a voluminous "Colorado Basin Water Supply and
Demand Study" to assess likely imbalances over the half century
The aim was to provide a technical foundation for what are
likely to be difficult negotiations among the basin states,
federal agencies and the U.S. Congress over how to update past
agreements and share the river water sustainably in future.
STATE OF EMERGENCY
Long-term drought across much of the west is being
compounded by a short-term downturn in rainfall in California
and a number of other states, leaving them acutely short of
On Jan. 17, California's governor declared a state of
emergency and directed officials to take all necessary measures
to cut water consumption and boost supplies. Local water
providers were ordered to activate contingency plans to try to
forestall outright restrictions that could still be necessary
later in the year.
California's rainfall is highly variable. Droughts are
common. The worst one in recent times occurred between 1928 and
1934, which saw the lowest rainfall since the mid-1500s, and
provided the backdrop to John Steinbeck's novel "East of Eden".
Other significant droughts occurred in 1976-77, 1987-1992
and 2007-2009, according to the state Department of Water
California receives about three quarters of its yearly
rainfall between November and March in the form of a small
number of storms.
"A few storms more or less during the winter season can
determine if the year will be wet or dry," the department
explains on its website. "If a persistent Pacific high pressure
zone remains over California in mid-winter, there is a tendency
for the year to be dry."
The winters of 2011/12 and 2012/13 saw very low rainfall.
Now the state is experiencing its third dry winter in a row,
pushing water resources to critical levels.
Just 3.3 inches of rain and snow fell across the Northern
Sierra region between October and December, less than 20 percent
of the normal amount.
On Dec. 31, the state's key reservoirs contained only 65
percent of their normal amount of water. Four of the 12 main
reservoir systems had under 50 percent of their normal water. By
Feb. 7, total storage had fallen to 58 percent of the norm.
California depends on winter rainfall, as well as snow melt
from mountains, for its water supplies as well as the
hydroelectric power which provides a large share of the state's
But with reservoirs already critically low, the state will
have to rely heavily on its allocation of water from the
Colorado River as well as groundwater supplies from the giant
aquifers beneath the Central Valley.
The problem is that aquifers across California and much of
the rest of the west and southwest United States have been
depleting as homes, businesses and especially farmers extract
water from them faster than it can be replenished.
Between 1900 and 2008, the 40 most important aquifers in the
United States lost almost 1,000 cubic kilometres of water as a
result of depletion, according to the U.S. Geological Survey
("Groundwater Depletion in the United States", 2013).
Nearly all the losses occurred in the west and southwest.
California's Central Valley aquifers have lost almost 145 cubic
kilometres of water since 1900. Other western aquifers lost 177
Aquifers along the Gulf Coast (stretching from Florida to
Texas) lost 266 cubic kilometres. The High Plains or Ogallala
aquifer (which runs from South Dakota down to Texas) lost a
staggering 340 cubic kilometres. In the worst-affected parts of
the Ogallala, the water table has dropped more than 150 feet.
The rate of depletion appears to be accelerating. The High
Plains aquifer lost an average of 10 cubic kilometres a year
between 2000 and 2008, while Central Valley lost an average of 4
cubic kilometres of water, according to the USGS.
The Central Valley is one of the biggest agricultural areas
in the United States. The underlying aquifer depends on run-off
from the Sierra Nevada to its east and the Klamath Mountains in
the north to recharge. But groundwater supplies have been under
pressure for some time. Falls in the water table were recorded
as long ago as the 1930s.
By the 1980s, there were 100,000 high-capacity groundwater
wells for irrigation or municipal supply, according to USGS.
During the 1976-77 drought, they pumped a staggering 18.5 cubic
kilometres of water out of the aquifer. By 1980, the water level
in some wells had declined by 200 feet. There has been
widespread and severe subsidence.
Water use in California as well as much of the west and
southwest is clearly unsustainable. But proposals to bring large
volumes of water in from rivers in the Pacific Northwest, Canada
or even Alaska, through giant canals or even pipelines, are
There is a pressing need to curb regional water consumption.
However, effective water management has eluded the region since
it opened up for homesteaders in the 19th century.
State and local governments are no closer to solving the
problem, so water shortages seem set to worsen in the next few
years unless the west and southwest get luckier with rainfall.
(Editing by Dale Hudson)