9. Lakes and ponds are inland bodies of standing or slowly moving water.
Although lakes and ponds cover only 2 percent of the world's land
surface, they contain most of the world's fresh water. Individual lakes
and ponds range in area from a few square meters to thousands of
square kilometers.
ponds are smaller than lakes, though regional idiosyncrasies of naming
abound—Henry David Thoreau's famous Walden Pond in Massachusetts
has a surface area of 64 acres. Lakes and ponds are an important source
of fresh water for human consumption and are inhabited by a diverse
suite of organisms.
10. A stream is a body of water that flows on Earth’s surface. The word stream is often used
interchangeably with river, though rivers usually describe larger streams.
Streams provide many benefits to humans. Besides providing drinking water and irrigation for
crops, streams wash away waste and can provide electricity through hydropower. People often
use streams recreationally for activities such as swimming, fishing, and boating. Streams also
provide important habitat for wildlife.
Streams need two things to exist: gravity and water.
Streams create channels by wearing down rock and carrying it and other sediment downstream.
11. A river is a natural flowing watercourse, usually freshwater, flowing towards an ocean, sea, lake
or another river. In some cases a river flows into the ground and becomes dry at the end of its
course without reaching another body of water. Small rivers can be referred to using names such
as stream, creek, brook, rivulet, and rill. There are no official definitions for the generic term river
as applied to geographic features,[1] although in some countries or communities a stream is
defined by its size. Many names for small rivers are specific to geographic location; examples are
"run" in some parts of the United States, "burn" in Scotland and northeast England, and "beck"
in northern England. Sometimes a river is defined as being larger than a creek,[2] but not always:
the language is vague.[1]
Rivers are part of the hydrological cycle. Water generally collects in a river from precipitation
through a drainage basin from surface runoff and other sources such as groundwater recharge,
springs, and the release of stored water in natural ice and snowpacks (e.g., from glaciers).
12. The pool of water created by the construction of a dam across a river is called reservoir. When the reservoir remains
in water supply during the rainy season and releases it during dry period as per requirement, it is called storage or
impounded reservoir.
The storage reservoir is generally constructed on the notion – a perennial river which cannot supply water during
the summer season with the storage reservoir, the flow of water in the river is regulated.
The various purposes for which the storage works are required are
Irrigation
Hydro-electric power generation
Domestic and industrial water supply
Control of destructive floods
Low water regulation for generation
Recreation
Preservation and breeding of useful aquatic life
13.
14.
15. A tube well is a type of water well in which a long, 100–200 millimetres (3.9–7.9
in)-wide, stainless steel tube or pipe is bored into an underground aquifer. The
lower end is fitted with a strainer, and a pump lifts water for irrigation. The
required depth of the well depends on the depth of the water table.
In tube wells the metal pipe driven in ground is perforated to allow only clear water to enter the
hole. It is obvious that if no other means is adopted the perforations in the metal tube will have
to be made very fine. It is very costly process.
As an alternative wire net may be wrapped on the cylindrical frame of small diameter but it is
liable to break as it is very delicate. So the best and most commonly adopted practice is to
provide a pipe with fairly big perforations and surrounding that is a wire net or a strainer with
smaller openings.
16. A spring may be the result of karst topography where surface water has infiltrated
the Earth's surface (recharge area), becoming part of the area groundwater. The
groundwater then travels through a network of cracks and fissures—openings
ranging from intergranular spaces to large caves. The water eventually emerges
from below the surface, in the form of a karst spring.
The forcing of the spring to the surface can be the result of a confined aquifer in
which the recharge area of the spring water table rests at a higher elevation than
that of the outlet. Spring water forced to the surface by elevated sources are
artesian wells. This is possible even if the outlet is in the form of a 300-foot-deep
(91 m) cave. In this case the cave is used like a hose by the higher elevated
recharge area of groundwater to exit through the lower elevation opening.
