They are fashioned to capture the rain so the water will trickle down and replenish the aquifer eventually giving rise to water in the wells and bringing dead rivers back to life.
At the Rain Centre, Mr Sekhar, a physics professor, demonstrates that rain falling on a typical Chennai flat roof can be gathered for use by the household in the kitchen and bathroom, and the rest channelled into wells where it can be used or go to replenish the water table.