ABSTRACT: Tourism leads to a drastic and mostly irreversible change of the behaviour of indigenous population of the dry areas concerning water usage. Southern Tunisia Oasis: Douz, Tozeur and Nefta are an area where such process takes place. The tourist who reaches the southern part of Tunisia is often the ‘beach’ tourist who took an optional trip, not particularly sensitive as far as cultural diversity and ecological problems are concerned. In this case it is hard to speak of any kind of water economy. Nevertheless, it is important to notice that there is no information in the hotels about the limited amount of water. What is more, water resources are even more drastically wasted by the hotel service. For local population which is used to economical water usage, watching such behaviour is both a ‘cultural shock’and a sort of ‘discovery’. They learn that water is not a ‘limited’ resource, hence it can be used for other purposes – such as for unlimited irrigation of crops – as well. As a result, the highest water usage (often water waste) is observed in the agricultural sector, not in the tourism sector. Yet it is hard to refute that this kind of imprudent behaviour is an indirect effect of the development of tourism.