Analytical study on probability distribution of critical hydrological drought duration

YUAN Chao1,SONG Song-bai1,JI Ping2 (1 College of Water Resource and Architectural Engineering,Northwest A&F University,Yangling,Shaanxi 712100,China;2 People's Government of Wuquan Town,Yangling District,Yangling,Shaanxi 712100,China)

critical hydrologic drought duration;probability distribution;return period;P-Ⅲ distribution;Markove

【Objective】 The variation of the probability distribution of critical hydrological drought duration with hydrological parameters of runoff which was followed with P-Ⅲ distribution and Markove process was made.【Method】 Based on the theory of run and extremes of random number of random variable and taking North Luo River and Jing River as examples,the probability distribution of critical drought duration in a certain period and the variation of the probability distribution and expected value of critical drought duration with first-order auto-correlation coefficient and skewed coefficient were completed.【Result】 In a certain period,the probability and expected value of critical drought duration got larger with the increase of first-order autocorrelation coefficient and skewed coefficient,especially with first-order auto-correlation coefficient.The return periods of consecutive 11-year drought in North Luo River and Jing River were 1 000 years.【Conclusion】 The analytical method in this paper avoided much calculation caused by simulation and had the traits of high accuracy and convenience,so it could be used in meteorological drought analysis.