Wasting water

Q: There is a Muslim brother who waters his lawn all day. The water runs off on to the road. I as a Muslim know that water is a gift from Allah Ta'ala. How do I approach my fellow Muslim brother in Islam and tell him not to waste this precious gift from Allah Ta'ala? His neighbours who are Hindus only water their lawn for a few hours and it does not run on to the road. The saddest thing is he is a Moulana.