Justifiability of Tayammum when one is almost sure of not finding water

Q: Respected Shaykh, we sometimes leave the city of Riyadh to spend some days in the desert. We have more than one car on which we carry a tank or more of water to use it for drinking, cooking, washing dishes, and so on. In the evening, we camp in a place which is twenty kilometers or more or less away from the nearest place where water is available. Some of us perform Tayammum (dry ablution with clean earth) to offer the Salah under the pretext that the water we have is only used for drinking, cooking, washing dishes, and so on, whereas others perform Wudu' (ablution), saying that water is available and any of us can go by car to get water from the nearest village or petrol station at any time. Also, we shorten the Salahs (Prayers) and combine the `Isha' (Night) Prayer with the Maghrib (Sunset) Prayer and the Zhuhr (Noon) Prayer with the `Asr (Afternoon) Prayer, although we stay in the same place for more than one Salah. For example, we may stop at a place before the Maghrib Prayer and leave it after (Part No. 4; Page No. 181) the Fajr (Dawn) Prayer. Also, we may stop at a place before the Zhuhr Prayer and leave it after the `Asr Prayer, and so on.Respected Shaykh, is it permissible for us in such a case to perform Tayammum to offer Salah? Also, is it permissible for us to shorten the four-Rak`ah Salah (Prayer consisting of four units) to two-Rak`ah Salah or to combine the Maghrib Prayer with the `Isha' Prayer or the Zhuhr Prayer with the `Asr Prayer, although the distance to our home city, Riyadh, is most probably more than one hundred kilometers. If there is a fixed distance for shortening the Salahs, we will be grateful if you could mention it. May Allah reward you with the best. May Allah prolong your life and extend the benefit of your knowledge to all Muslims.

A: Allah (Glorified be He) permitted Tayammum and made it a substitute for water when it is not available or difficult to get, or when one is unable to use water because of an illness or any other legal excuse. Also, Allah made it obligatory to use water for Wudu' when water is available and not difficult to get. Allah (Exalted be He) says: 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. 4; Page No. 182) Since you can get water for your Wudu' and your personal needs, such as drinking and other purposes, from the villages and the stations you pass by on your way, which are no more than twenty kilometers away from you, it is obligatory for you to use water for Wudu'. It is not permissible for you to perform Tayammum instead, as Tayammum will not be sufficient for you to perform Salah. This is because you fall under the same ruling as those who have water, because you can get it by your cars. Therefore, you are not excused for performing Tayammum in such a case. The person who has an excuse for performing Tayammum is the one who is almost sure that he will not find water if he searches for it, or a person who fears death due to searching for water, or fears that he may miss the due time of a particular Salah. The distance that allows shortening Salahs is eighty kilometers, as agreed upon by the Jumhur (dominant majority of scholars). Consequently, it is permissible for you to shorten the four-Rak`ah Salah to two Rak`ahs over this distance, and to combine the Zhuhr Prayer with the `Asr Prayer and the Maghrib Prayer with the `Isha' Prayer at the due time of any of the two combined Salahs, whether the earlier or the later one.May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.