Keeping flowers in a bowl filled with water in front of main entrance of houses is considered as auspicious as per Indian tradition.
This helps to maintain harmony among family members as well as neighbours.
It is proven fact that flowers have a quality of soothing stressed mind , this will be reason for keeping flowers in front of door and also may be for welcoming.
The water in bowl will be for preserving the flower till evening. Whatever , the flowers seems very beautiful.