Environmental Engineering Reference
In-Depth Information
Unconfined Aquifer Recharge Area
Evaporation and transpiration
Evaporation
Precipitation
Confined
Recharge
Area
Runoff
Flowing
artesian well
Recharge
Unconfined
Aquifer
Stream
Well
requiring
a pump
Water
table
Water
table
Infiltration
Infiltration
Lake
Infiltration
Infiltration
Unconfined aquifer
Confined aquifer
Figure 11-3
Natural capital:
groundwater system. An
unconfined aquifer
is an aquifer with a water table. A
confined aquifer
is bounded above and below by less permeable beds of rock. Groundwater in this type of
aquifer is confined under pressure. Some aquifers are replenished by precipitation; others are not.
To meet the demands of our growing population,
global withdrawal rates of surface water could reach
more than 70% of the reliable runoff by 2025 and 90%
if per capita withdrawal of water continues increasing
at the current rate. This is a global average. With-
drawal rates already exceed the reliable runoff in some
areas.
water withdrawn each year, and cities and residences
use the remaining 10%.
Manufacturing and agriculture use large amounts
of water. For example, it takes 400,000 liters (106,000
gallons) of water to produce an automobile, 9,000 liters
(2,800 gallons) to produce 1 kilogram (2.2 pounds) of
aluminum, and 7,000 liters (1,900 gallons) to produce
1 kilogram (2.2 pounds) of grain-fed beef. You could
save more water by not eating a half a kilogram
(1 pound) of grain-fed beef than by not showering for
six months.
Global Outlook: Uses of the World's
Fresh Water
Irrigation is the biggest user of water (70%), followed
by industries (20%) and cities and residences (10%).
Worldwide, we use 70% of the water we withdraw
each year from rivers, lakes, and aquifers to irrigate
one-fifth of the world's cropland. This land produces
about 40% of the world's food, including two-thirds of
the world's rice and wheat. Industry uses 20% of the
Science Case Study: Freshwater Resources
in the United States
The United States has plenty of fresh water, but
supplies vary in different areas depending on
climate.
