A scenario is a consistent description of a possible future situation, a story about the way the world might turn out tomorrow. Developing a set of narrative scenarios helps to identify possible pathways (strategies) towards a shared vision of the future, based on current trends together with knowledge of the sources of greatest uncertainity in those trends. A scenario is not a forecast or prediction; rather it is a plausible story about the future with a logical plot and narrative governing the manner in which events unfold (Schwartz, 1991). Scenario analysis or development may be defined an approach or method in water sector planning for dealing with uncertainties in the distant future, and aims to assess possible impacts and to design policies (e.g. Carter et al., 2007).There can be normative and explorative scenarios.Scenarios can entail a sequence of possible events leading from the present situation to certain future conditions. It can also merely represent a story of a future or a specific event in the future. Some scenarios might also represent a desired long-term future vision. Exploratory scenarios probe the future starting from the present, while normative or back-casting scenarios begin with a description of the desired future vision and work backwards to the present. Normative scenarios describe a pre-specified future, presenting "a picture of the world achievable (or avoidable) only through certain actions” (IPCC). The external context of scenarios is important: scenarios are mainly driven by autonomous external forces that are hard (if not impossible) to influence. Both types identify the major driving forces and uncertainties and evaluate possible consequences and vulnerabilities. Different strategies and decisions can be assessed for each scenario, which will give an indication of the ‘robustness’ of different actions. Robust actions perform well under a wide variety of possible futures or are flexible to adapt in case the future runs out differently than foreseen.