Hawzah News Agency – Ayatollah Khamenei answers a question pertaining to the rules of the lavatory.
Q: The nomadic tribes do not have sufficient water, especially during the days of their migration, for purifying the urinary outlet. Is it sufficient to purify it with wood or pebbles? And can they offer their prayers in such a situation?
A: The urinary outlet cannot be purified except by water. But if it is not possible to purify it with water, the prayer will be valid.
Source: https://www.leader.ir/en/book/32/Practical-Laws-of-Islam