“…Not a single answer exists for such a question. Institutionalists (Bakker et al,1998;Kenney, 1995;O´Riordian and A.Jordan, 1999;Ostrom, 1990); economists (Beare et al, 1998;Howe and Smith, 1994); modellers (Dudley and Hearn, 1993;Garrido and Gómez-Ramos, 2000); geographers (Emel and Roberts, 1995), engineers (Harding et al, 1995); sociologists (Keenan and Krannich, 1997); and statisticians (Tarboton, 1995;Hobbs, 1997), among others, contribute with alternative and non-exclusive explanations of why societies experience periods of water shortages. Several authors argue that attenuated property rights over State-managed water bodies are conducive to dominant non-cooperative strategies pursued by rights-holders in their game with water managers to secure water access in uncertain hydrological conditions (Lise et al, 2000).…”