(Posted to science for the people mailing list by Marshall Ambros.)
It would be great if people started to use less water at their home, but
the statement, "best Foods has swapped its dishes for paper plates and
foam cups," is very scary - if everyone did this than all our hills
would become landfills.
It is important to fully understand who is using the water so I have
attached an article from the US Geological Survey which gives some
figures. Using this data I have calculated that, for total fresh water
usage in the USA:
Irrigation uses 137 Bgal/d: 39.6 percent
Thermoelectric power uses 135 Bgal/d: 39.1 percent
Public water supply uses 43 Bgal/d: 12.5 percent
Further, Public water supplies 85 percent of all residences. If it is
assumed that residences with private water supply (15 percent of total)
use roughly the same amount as a residence with public water supply,
then ((43 multiplied by 0.15) plus 43) is equal to:
Residential water supply uses 49.45 Bgal/d: 14.3 percent
These are rough figures.
If people were to cut their use of water at home in half, it would be
equivalent to reducing Irrigational use by a less than a fifth.
Reduction in residential usage of water has limited return because of
it's small percentage, though maybe this is an area where water usage is
most easily reduced. In order to have a significant reduction in
national fresh water usage we will need to encourage drip irrigation
over sprinklers and power generation systems that are not thermoelectric
- or use of salt water in thermoelectric plants. (Power plants that use
thermoelectric power generation are coal and nuclear).
Marshall Ambros
[EMAIL PROTECTED]
http://pubs.usgs.gov/circ/2004/circ1268/
Estimated Use of Water in the United States in 2000
ABSTRACT
Estimates of water use in the United States indicate that about 408
billion gallons per day (one thousand million gallons per day,
abbreviated Bgal/d) were withdrawn for all uses during 2000. This total
has varied less than 3 percent since 1985 as withdrawals have stabilized
for the two largest uses—thermoelectric power and irrigation. Fresh
ground-water withdrawals (83.3 Bgal/d) during 2000 were 14 percent more
than during 1985. Fresh surface-water withdrawals for 2000 were 262
Bgal/d, varying less than 2 percent since 1985.
About 195 Bgal/d, or 48 percent of all freshwater and saline-water
withdrawals for 2000, were used for thermoelectric power. Most of this
water was derived from surface water and used for once-through cooling
at power plants. About 52 percent of fresh surface water withdrawals and
about 96 percent of saline-water withdrawals were for
thermoelectric-power use. Withdrawals for thermoelectric power have been
relatively stable since 1985.
Irrigation remained the largest use of freshwater in the United States
and totaled 137 Bgal/d for 2000. Since 1950, irrigation has accounted
for about 65 percent of total water withdrawals, excluding those for
thermoelectric power. Historically, more surface water than ground water
has been used for irrigation. However, the percentage of total
irrigation withdrawals from ground water has continued to increase, from
23 percent in 1950 to 42 percent in 2000. Total irrigation withdrawals
were 2 percent more for 2000 than for 1995, because of a 16-percent
increase in ground-water withdrawals and a small decrease in
surface-water withdrawals. Irrigated acreage more than doubled between
1950 and 1980, then remained constant before increasing nearly 7 percent
between 1995 and 2000. The number of acres irrigated with sprinkler and
microirrigation systems has continued to increase and now comprises more
than one-half the total irrigated acreage.
Public-supply withdrawals were more than 43 Bgal/d for 2000.
Public-supply withdrawals during 1950 were 14 Bgal/d. During 2000, about
85 percent of the population in the United States obtained drinking
water from public suppliers, compared to 62 percent during 1950. Surface
water provided 63 percent of the total during 2000, whereas surface
water provided 74 percent during 1950.
Self-supplied industrial withdrawals totaled nearly 20 Bgal/d in 2000,
or 12 percent less than in 1995. Compared to 1985, industrial
self-supplied withdrawals declined by 24 percent. Estimates of
industrial water use in the United States were largest during the years
from 1965 to 1980, but during 2000, estimates were at the lowest level
since reporting began in 1950. Combined withdrawals for self-supplied
domestic, livestock, aquaculture, and mining were less than 13 Bgal/d
for 2000, and represented about 3 percent of total withdrawals.
California, Texas, and Florida accounted for one-fourth of all water
withdrawals for 2000. States with the largest surface-water withdrawals
were California, which had large withdrawals for irrigation and
thermoelectric power, and Texas, which had large withdrawals for
thermoelectric power. States with the largest ground-water withdrawals
were California, Texas, and Nebraska, all of which had large withdrawals
for irrigation.
