The network of pipes which carries waste water to water treatment plant is called _____.

One of the important factors, that can lead to a scarcity of water, is -

Due to increase in population, the demand for usable water has increased whereas it's availability has _______.

The top level of the ground water is called______.

Use of _______ and _____ for irrigation reduces wastage of water.

Three methods of drawing out ground water are-

Which among the following is a method to avoid wastage of water?

Only ______ percent of water on the earth is fresh water.

Unnecessary, cutting down of trees will cause an increase in the level of ________ gas, which causes global warming.