The drought frequency index (DFI) is employed in this study as a drought indicator and as a trigger mechanism for multireservoir system operations during drought. The DFI characterizes droughts according to their duration and intensity, using a probabilistic criterion that takes into account the persistence of extreme low precipitation values. Performances with and without the DFI are evaluated, using reliability and resilience indices, for the Conchos river basin—a tributary of the Rio Grande/Bravo basin between United States and Mexico—through a multilevel nonlinear optimization procedure oriented to reduce water deficits to the United States and maximize net benefits for farmers in Mexican irrigation districts. Results show that the inclusion of the DFI improves the reliability of both reservoirs and water deliveries to users during periods of drought, which reflects an overall improvement of net benefits associated with crop production in Mexican irrigation districts.