We discuss the human role in hydropower system control, noting how it is different from other supervisory control environments and the typical shortcomings in current displays provided to hydropower system controllers. We describe steps towards evaluating proposed functional displays with the industry hydropower controllers. This involves selecting test scenarios that may demonstrate the advantages, if any, of the functional displays. Starting from a basic human control loop: detect analyse act evaluate, we identify scenarios in which the functional displays are expected to provide information in a more effective way than current displays.