A 50-year annual series of peak discharges is described by the log-normal distribution. The geometric mean of the series is 60,000 cfs and the standard deviation of the log of the discharges is 0.43.
(1) Determine the discharge with a recurrence interval of 25 years.
(2) Determine the discharge with a recurrence interval of 100 years.
(3) Find the recurrence interval associated with a discharge of 100,OOO cfs.
(4) What is the probability that a discharge of 100,OOO cfs will be equaled or exceeded in the next 15 years?