Question

why is rain water harvesting a ray of hope for overcoming the present scarcity of water in cities

Answer 1

As compared to villages cities are having less no. of source of water.
To meet the needs of each and every citizen in cities, rain water harvesting is the best idea to overcome the scarcity of water.

Answer 2

$\huge\mathbb{ANSWER:-}$

Rainwater harvesting is a 'ray of hope' for overcoming the present 'scarcity of water' in cities as rain water harvesting can supplement the requirement of water in cities and raise the sub-soil water level. This can help to maintain greenery in urban areas.