When water is 50 kms far from the person, they are not excused to perform Tayammum
All praise be to Allah Alone, and peace and blessings be upon His Messenger, and his family and Companions.
Allah (Exalted be He) has made it obligatory to perform Wudu’ and Ghusl when water is available, and He also made it obligatory to perform Tayammum when water is not available or when it is difficult to use due to an illness or the like. Allah (Exalted be He) says (what means),
O you who believe! When you intend to offer As-Salât (the prayer), wash your faces and your hands (forearms) up to the elbows, rub (by passing wet hands over) your heads, and (wash) your feet up to ankles. If you are in a state of Janâba (i.e. after a sexual discharge), purify yourselves (bathe your whole body). But if you are ill or on a journey, or any of you comes after answering the call of nature, or you have been in contact with women (i.e. sexual intercourse), and you find no water, then perform Tayammum with clean earth and rub therewith your faces and hands.
(Part No. 5; Page No. 332) Since you obtain water for camels and cattle, then water is available. Consequently, performing Wudu’ and Ghusl is obligatory on you. Living in the desert with the nearest water source fifty kilometers away is not a valid excuse to perform Tayammum, as long as you can get water on your vehicles for the camels and cattle. Allah knows best.May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.