Design Criteria for Hydrologic Extremes

Hydrologic extremes such as floods and low flows are treated as independent random variables. Accordingly, probabilistic models are derived for two approaches of adopting hydrologic extremes as design criteria in water resources project planning. One approach is to use the hydrologic event of a given recurrence interval, and the other is to use the extreme event observed in the record. The models are verified agreeably by the flood data of 10 Illinois rivers. Both models give essentially the same results when the period of design is less than one-tenth of the recurrence interval and the length of record. Also, by the Monte Carlo method, synthetic hydrologic extremes are generated by a time-series model for use in water resources systems analysis.