The Congress theme "Balance and Uncertainty: Hydraulic Engineering in a Changing World" focuses on the central roles of hydraulic engineering, hydrology, and water resources for our changing world, and how these roles link to the broader issues. A balance is continually being sought between competing values in water engineering, including the environment, the economy, tourism, social and indigenous values, health aspects, aesthetics, and the needs of current and future generations. Careful management and innovative solutions are required to balance these competing values, and these solutions must be able to deal with the uncertainty in the natural world as well as the changing human world.