Rainwater can be harvested in the following ways :(any four points)
i) By digging ponds and tanks.
ii) By building embankments and check dams.
iii) By making arrangements for storage of rainwater on rooftops.
iv) By constructing concrete underground reservoirs.
v) By constructing reservoirs in park and public places and covering them with concrete slabs.
vi) Building plans should invariably be made only when there is a provision for water harvesting.

The different causes of water pollution are:
(a) Mix-up of domestic wastes
(b) Mix-up of Industrial wastes,
 (c)Use of Chemicals, pesticides and fertilizers used in agriculture
 (d) Oil slicking by ships in oceans