The correct options are
A Conservation of water
C Improvement of groundwater level
Rainwater harvesting is a technique used for collecting, storing and using rainwater. It can be done for groundwater refilling or for conserving water for day-to-day use.
During rainfall, water is stored on the top of rooftops and concrete roads. This water is guided via pipes to be stored in tanks or reservoirs for future use. It can be made to seep through the ground so as to increase the underground water level.