If a person has wuḍūʾ and knows that if he invalidates his wuḍūʾ it will not be possible to find water or he will not be able to perform wuḍūʾ, then in the event that he can keep his wuḍūʾ, based on obligatory precaution, he must not invalidate his wuḍūʾ, whether that be before or after the time for prayers has set in. However, one can have sexual intercourse with his wife even if he knows that he will not be able to perform ghusl.