Planning a century in advance may seem futile. The problem with not planning for long-term objectives is that water infrastructure is expensive and once built it is very hard to detach from the dependencies it creates. It is easy to plan for the short term and build infrastructure that will support a vibrant economy today. It is harder to deconstruct that economy when the water supply is no longer reliable or the quality is no longer usable. The state of the art of climate prediction is still not great, but it is far better than it used to be. In ten years’ time, the forecast for 2117 will be different than our current 100-year projection, but it probably won’t be wildly different. The adjustments in planning that will be needed to stay on course will be minor (probably!). None of this is without uncertainty, but we are also getting much better at understanding, communicating and planning with uncertainty.