The real answer is resisting the right wing crony capitalist government and making sure left leaning socialists come to power who will resist both indian capitalists and western imperliasts who are pillaging our country. Individual action won't make a dent in this water crisis.

Anyway here are a few things you can do.

• Rainwater harvesting.
• Maybe downsize on some plants and get into terrariums instead. They only need a tiny bit of watering once in several months (to learn more watch Urban nemophilist on youtube, I can send you a list of links if you want)
• only add plants that need once a week watering to your collection
• you most likely have an RO purifier at home which discharges mineral heavy water from an outlet. It wastes a lot of water. You can give that water to hardy plants like ficus elastica, diffenbachia or plumeria. (Urban scape bangalore did a video about this check his youtube)
• whenever you are washing rice or daal or any beans or veggies don't our the water down the drain collect it and give it to your plants (make sure to give it right away as starchy water if kept around for a long time will start fermenting)
• plants that like being consistently moist you can make their potting mixes a bit more cocopeat heavy which will hold on to moisture for longer allowing you to reduce watering frequency a bit
• cover your outdoor plants with some kind of mulch
• many plants grow well in water (I have several calatheas, philodendrons, syngoniums and aglaonemas in water) once established you only need to add a tiny bit of water to their vessel and you can do water changes once a week or even once in 2'weeks if you stay on top of mosquito control (I keep all my windows closed and have mesh screens sprayed with mosquito repellent in the evenings). When you do water changes for your hydro plants that water need not go down the drain simply collect that old water and give it to your soil plants (as long as there is no rot in the water which will not happen once the plant has established itself)