Document Type : Original Article
Authors
1 Water engineering department, university of birjand
2 Department of Water Engineering,Department of ِResearch Group of Drought and Climate Change Faculty of Agriculture,University of Birjand, Birjand, Iran.
Abstract
Drought is one of the most damaging natural events that should be considered by water resource planners due to its dominance in a geographical area and its long duration. Two obvious characteristics that should be taken into consideration in the study of drought are its intensity and duration. In this research, two-dimensional detailed functions were used to create bivariate distributions of drought intensity and duration in Qaen meteorological station during 1998-2018. To determine the severity and duration of drought, the 12-month Standardized Precipitation Index (SPI) time series was used. Tau-Kendall and Spearman correlation coefficients were used to determine the significance of the correlation between drought severity and duration, and their values were determined as 0.74 and 0.88, respectively. The results of examining the distribution of marginal probabilities showed that the duration and severity of drought follow the distribution of normal and log normal probability, respectively, and the parameters of these distributions were determined. Also, among the studied joint functions, the atmospheric joint function with RMSE value equal to 0.0924 and NSE index equal to 0.996 is the most suitable function for the analysis of the two variables of drought intensity and duration, and the maximum value of its logarithm is 7.87. Came. Finally, the probability of occurrence of two variables and the probability of return periods were calculated, and the results can provide valuable information for the planning and integrated management of water resources in the study area to the planners and stakeholders.
Keywords
- Bivariate analysis
- intensity and duration
- Qaen observation station
- precipitation
- marginal probability distribution
Main Subjects
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