A range of variables can be used, such as resource availability, consumption trends, climate change, population growth, or policy frameworks. Scenarios can help parties to understand the competition between various sectors, including irrigation, drinking water supply, hydropower generation, flood control and other ecosystem services, as well as the evolution and implication of existing and potential conflicts. Closely related to scenario-building is a technique called “back-casting", which envisions a future desirable outcome, and then tracks backwards, allowing parties to identify the steps that would be needed to achieve it. Agreement on a desirable future can then translate into agreement on the steps needed to get there.