Q: I notice that watering of graves is quite a common practice. Is there any Islamic reason why this practice takes place? What is the ruling?
A: It is permissible to sprinkle water on the Qabr immediately after burial. Rasulullah (Sallallaahu Alayhi wa Sallam) himself done this. (Raddul Muhtaar V6 P379).
It will be permissible afterwards also, if the intention is protection of the sand and to save it from dispersing. It will not be correct with any other intention.
Moulana Yusuf Laher