Page 164 - Science Class 06
P. 164
Underground Water : Groundwater is contaminants such as animal wastes,
water contained in or by a sub-surface pes cides, insec cides, industrial wastes,
layer of soil or rock. There are many algae and many other organic materials.
sources recharging the supply of ground- Even surface water found in what seems like
water, including rain that soaks into the pris ne mountain streams can be contami-
ground, rivers that disappear under- nated by wild animal wastes, dead animals
ground and mel ng snow. Because of
many sources of recharge, groundwater upstream or other decay.
may contain any or all of the contami-
nants found in surface water as well as
the dissolved minerals it picks up under- 1. Why life is not possible on the earth
ground. without water?
2. About 71% of the earth’s surface is
covered with water, s ll we face the
problems of its shortage. Why?
3. Write any four sources of surface water.
DROUGHT
A drought is when there is a lack of
precipita on over an extended period of
Hand Pump Electric Pump me, usually a season or more, resul ng in
a water shortage for some ac vities, groups,
How the amount of groundwater is
or environmental sectors. Its impacts result
maintained?
from the interplay between the natural
The main source of water for the ground- event (less precipita on than expected) and
water is rain. Whenever it rains, water the demand people place on water supply,
collects in the fields. This water percolates and human ac vi es can exacerbate the
down through the soil and reaches below impacts of drought.
the earth’s surface. Thus, the amount of
Causes of Drought
groundwater or the level of groundwater is
maintained. Absence of rain for a long spell or acute
rainfall within a geographical region is the
Surface Water : Surface water is just what
main cause of drought. Even one year
the name implies; it is water found in a
absence of rain or acute rainfall may cause
river, lake or other surface cavities. This
drought.
water is usually not very high in mineral
content, and is o en called “so water” Causes of low or no rainfall:
even though it is probably not. Surface v Deforesta on is the main cause behind
water is exposed to many different low rainfall.
164 Science-6
