Environmental Engineering Reference
In-Depth Information
Volcanic
steam
Water in the atmosphere
Condensation
Sublimation
Ice and
snow
Evapotrans-
piration
Precipitation
Desublimation
Evaporation
Fog
drip
Surface
runoff
Snowmelt runoff
Dew
Streamflow
Infiltration
Evaporation
Seepage
Flora and
fauna
Spring
Plant
uptake
Fresh-
water
Oceans
Vents and
volcanoes
Groundwater storage
FIGURE 28.1
Natural water cycle is a balance that is dependent on many different inputs. As human activity changes these
inputs, such as amount stored in groundwater or evapotranspiration from increased agricultural activity, the
cycle can be disrupted or altered. (From USGS. Summary of the Water Cycle . [cited February 18, 2013]; Available
http://ga.water.usgs.gov/edu/watercyclesummary.html, 2013.)
+37%
+20%
+68%
+81%
+29%
%
+10%
Projected
population
growth
To tal freshwater withdrawal, 1995/available precip.
percent, number of countries in parentheses
>=500
100 to 500
30 to 100
5 to 30
1 to 5
0 to 1
+36%
(49)
(207)
(303)
(740)
(1078)
(614)
FIGURE 28.2
Projected population growth by percentage and water shortages by color. Water shortage is deined as total
freshwater withdrawal divided by an area's precipitation, based on most recent available data. (From USDOE,
Energy Demands on Water Resources . US Department of Energy, 2006.)
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