A mixed integer linear programming (MILP) model for scheduling of the short-term operation of a price-taker hydroelectric plant is presented. The objective of the model is to maximize the profit of energy production in the next hours' operations. Non-linear production curves of hydro power units are considered through a piecewise representation. A detailed modeling of the hydro network is also described. Realistic test-cases of Los Molles and Sauzal-Sauzalito power plants, both part of the Enel group operations in Chile, are analyzed in detail. Results of real operation are compared to the schedules produced with the model showing the potential of the proposed approach in the industry.