Stochastic Depth-Duration Analysis and Estimate of Drought on Low Precipitation

Abstract

One of the many causes for drought is due to low precipitation, an amount below the mean value. In case it continues for several months, the occurrence of drought phenomena can be seen many times. A new method for depth-duration analysis (D-D analysis) concerning droughts, based on the characteristics and mechanisms with a time lapse of successive low precipitation, is discussed.
The definition of “duration preciptitation” is given first as precipitation accumulated for any duration of months beginning from any particular month. On the basis of monthly precipitation for the last several years, the occurrence probabilities of every duration precipitation for every month is derived stochastically.
Many interpretations and applications of the D-D analysis of low precipitation, according to the duration precipitation, are possible and shown:
1) Restoration or maintenance duration of low precipitation regarding any month is capable of being evaluated,
2) Maintenance and judgement of the design precipitation in any duration can easily be estimated with the occurrence probability regarding the residual duration precipitation after calculating the accumulated precipitation with a time lapse within its duration.
The same argument and interpretation on the occurrence probability of duration precipitation is applied to high precipitation, amount up the mean value, also.
The depth-duration analysis shown in this paper is an adequate method that could be applied to predicting and provisions for drought phenomena, and management and control planning of water resources.