Two complementary main lines are considered in this work. Firstly, the LCA of the water supply alternatives within the Segura Basin includes the environmental comparison of local alternatives (natural surface resources and ground waters), as well as the external ones: Tajo-Segura water transfer (TSWT) and seawater desalination. Base case (scenario 1) corresponded to the 2009 water balance. Irrigation and drinking water were distinguished in the analysis, since they presente significant differences. Two additional stages are required for drinking purposes: water supply network and water treatment plants. Once the base situation was analysed, three additional scenarios (2–4) were included in order to know, from the LCA approach, the environmental impact in wet and dry years, or the dependence from the TSWT. The four scenarios maintained the overall water demands on the watershed. Secondly, apart from water cycle infrastructures, the environmental impact of water consumption in this water scarce area was also calculated for the four different scenarios. The main purpose of this paper is then to show the combined LCA of the water supply alternatives and the water use in this water-stressed region in order to compare the environmental consequences, from the LCA perspective, of widening (or not) the supply options in order to reduce the depletion of local water resources.