Environmental Microbiology of Aquatic and Waste Systems

10 1 Nature, Properties, and Distribution of Water

3. Ground (or underground) waters:
   (a) Springs
   (b) Wells
   (c) Underground streams

1.4.2 Artificial Waters

Artificial waters, all of which are surface waters, are

man-made, and include:

1. Reservoirs


2. Dams


3. Oxidation ponds


4. Man-made lakes


5. Canals

1.5 Global Distribution of Water

on Earth and Its Study

Much of the world’s surface (71%) is covered by the

oceans, which have a mean depth of 3.8 km and whose

water is highly saline. The oceans and seas hold 97.5%

of all the world’s waters, the remaining 2.5% being

freshwater. Of this freshwater, 68.9% is locked in gla-

ciers and ice-sheets, while most of the rest (29.9%) is

groundwater. Much of the world’s freshwater is held

in rivers and lakes and constitutes 0.3%. Figure 1.5 and

Table 1.3 show the global distribution of water.

The seas and oceans of the world form a continuous

body of water which are linked to each other. They are,

Earth’s water Freshwater

Saline

(oceans)

97%

Fresh

surface water

(liquid)

Fresh

water 3% Other 0.9%

Surface

water

Ground 0.3%

water

30.1%

Icecaps

and

Glaciers

68.7%

Rivers 2%

Swamps 11%

Lakes

87%

Distribution of Earth’s Water

Fig. 1.5 Global distribution

of water (From http://ga.

water.usgs.gov/edu/

waterdistribution.html.

With permission)

Credit: United States

Geological Services (USGS))

Water source

Water volume

(cubic kilometers)

Percent of

freshwater

Percent of

total water

Oceans, seas, and bays 1,338,000,000 – 96.5

Ice caps, glaciers,

and permanent snow

24,064,000 68.7 1.74

Groundwater 23,400,000 – 1.7

Fresh 10,530,000 30.1 0.76

Saline 12,870,000 – 0.94

Soil moisture 16,500 0.05 0.001

Ground ice and permafrost 300,000 0.86 0.022

Lakes 176,400 – 0.013

Fresh 91,000 0.26 0.007

Saline 85,400 – 0.006

Atmosphere 12,900 0.04 0.001

Swamp water 11,470 0.03 0.0008

Rivers 2,120 0.006 0.0002

Biological water 1,120 0.003 0.0001

Total 1,386,000,000 – 100

Table 1.3 Volumes of water
in global water bodies
(Modified from Gleick 1996 )