This paper is on the problem of short-term hydro scheduling, particularly concerning a head-dependent hydro chain. We propose a novel mixed-integer nonlinear programming approach for optimizing power generation efficiency. The proposed approach considers not only the nonlinear dependence between power generation, water discharge and head, but also discontinuous operating regions, in order to obtain more realistic and feasible results. Numerical results, based on one of the Portuguese cascaded hydro systems, illustrate the proficiency of the proposed approach. Finally, conclusions are duly drawn.