Environmental Engineering Reference
In-Depth Information
discussed in more detail in Chapter 4 but is presented here briefly to allow
for discussion of water available for human use. The total runoff from land
to oceans via rivers has been reported as 22,100, 30,000, and 35,000 km 3
per year by Leopold (1994), Todd (1970), and Berner and Berner (1987),
respectively. These estimates vary because of uncertainty in gauging large
rivers in remote regions. Next, I discuss demands on this potential upper
limit of sustainable water supply.
HUMAN UTILIZATION OF WATER: PRESSURES ON A KEY RESOURCE
People in developed countries generally are not aware of the quantity
of water that is necessary to sustain their standard of living. In North
America particularly, high-quality water often is used for such luxuries as
filling swimming pools and watering lawns. Perhaps people notice that
their water bills increase in the summer months. Publicized concern over
conservation may translate, at best, into people turning off the tap while
brushing their teeth or using low-flow showerheads or low-flush toilets.
Few understand the massive demands for water by industry, agriculture,
and power generation that their lifestyle requires (Fig. 1.3).
Some of these uses such as domestic require high-quality water, and
others, such as hydroelectric power generation and industrial cooling,
Total
Industry
Irrigation
Domestic
A
600
400
200
0
300
3000
B
2500
200
2000
1500
100
1000
Population
Per capita use
500
0
0
1950
1960
1970
1980
1990
2000
Year
FIGURE 1.3 Estimated uses of water (A), total population and per capita water use (B) in
the United States from 1950 to 1990 [after Gleick (1993) and Solley et al. (1983)]. Note that
industrial and irrigation uses of water are dominant. Offstream withdrawals used in these es-
timates do not include hydroelectric uses.
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