Geology Reference
In-Depth Information
Table 1
Inventory of water at the Earth's surface
Volume 10
6
km
3
(10
18
kg)
Reservoir
Per cent of total
Oceans
1400
95.96
Mixed layer
50
Thermocline
460
Abyssal
890
Ice caps and glaciers
43.4
2.97
Groundwater
15.3
1.05
Lakes
0.125
0.009
Rivers
0.0017
0.0001
Soil moisture
0.065
0.0045
Atmosphere total
a
0.0155
0.001
Terrestrial
0.0045
Oceanic
0.0110
Biosphere
0.002
0.0001
Approximate total
1459
Source: Global Environment: Water Air Geochemical Cycles by Berner/Berner,
r
1996.
Adapted by permission of Prentice-Hall, Upper Saddle River, NJ.
3
a
As liquid volume equivalent of water vapour.
for India (86%, 5%, 8%), and 76% for Bangladesh (96%, 1%, 3%).
2
Many developing countries are using up to 40% of their renewable
freshwater for irrigation.
2
As a consequence of population growth,
pollution and climate change, the average supply of water per person is
likely to drop by one-third over the next two decades,
4
with a global
supply crisis projected to occur between 2025 and 2050, although much
earlier for some individual countries.
1,2,4
The quality of freshwater is also of concern. For example, about 75%
of Europe's drinking water is taken from groundwater,
2
a resource
described as overexploited in almost 60% of European industrial and
urban centres and threatened by pollutants.
5
River and lake eutrophica-
tion caused by excessive phosphorus and nitrogen from agricultural,
domestic, and industrial euents is a problem across most of Europe.
The Eastern European countries in particular fare badly when judged
against the criteria of pathogenic agents, organic matter, salinization,
nitrate, phosphorus, heavy metals, pesticides, acidification, and radio-
activity, and even the Nordic countries of Norway, Sweden, and Fin-
land, despite having generally better freshwater conditions than the rest
of Europe, suffer from acidification.
5
In Asia, 86% of all urban waste-
water and 65% of all wastewater is discharged, untreated, into the
aquatic environment.
6
There is also the unexpected and insidious
chemical contamination of apparently clean drinking water supplies,
exemplified most notably by the arsenic contamination of groundwater
that affects millions in Bangladesh and other Asian countries.
2
