1. Solution to water crisis
2.Sustainable, participatory, equitable management of water
3. To inculcate a culture of water conservation
4. To reduce soil erosion
5. To conserve surface water runoff during monsoon
6. To beneficiate water quality in aquifers 
7. To arrest ground water decline 
8. To agument ground water table
9. Collection of water for irrigation
10. Concious storage of water for domestic purposes 

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The Brainliest Answer!
Points regarding to your question:
1) it reduces soil erosion 
2) is suitable for irrigation
3) Reduces Demand on Ground Water
Reduces Floods
Can be Used for many Non-drinking purposes
will have a known quality of water
Reducing water bills and demand on your community’s drinking water supply by using rainwater for flushing toilets, washing clothes etc
Promotes both water and energy conservation
9) Requires some technical skills to install and provide regular maintenance
10) Limited and uncertain local rainfall
Hope This helps We just Had a activity on rainwater harvesting so these are the point which I remember
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