An analysis of non-normal Markovian extremal droughts

✍ Scribed by T. C. Sharma

• Publisher: John Wiley and Sons
• Year: 1998
• Tongue: English
• Weight: 259 KB
• Volume: 12
• Category: Article
• ISSN: 0885-6087
• DOI: 10.1002/(sici)1099-1085(19980330)12:4<597::aid-hyp596>3.0.co;2-n

✦ Synopsis

In many arid and semi-arid environments of the world, years of extended droughts are not uncommon. The occurrence of a drought can be re¯ected by the de®ciency of the rainfall or stream ¯ow sequences below the long-term mean value, which is generally taken as the truncation level for the identi®cation of the droughts. The commonly available statistics for the above processes are mean, coecient of variation and the lag-one serial correlation coecient, and at times some indication of the probability distribution function (pdf) of the sequences. The important elements of a drought phenomenon are the longest duration and the largest severity for a desired return period, which form a basis for designing facilities to meet exigencies arising as a result of droughts. The sequences of drought variable, such as annual rainfall or stream ¯ow, may follow normal, lognormal or gamma distributions, and may evolve in a Markovian fashion and are bound to in¯uence extremal values of the duration and severity. The eect of the aforesaid statistical parameters on the extremal drought durations and severity have been analysed in the present paper. A formula in terms of the extremal severity and the return period `T' in years has been suggested in parallel to the ¯ood frequency formula, commonly cited in the hydrological texts.