Regional Frequency Analysis of Drought Severity and Duration in Karkheh River Basin - Using Univariate L-Moments Method

Saeideh Parvizi (  [email protected] ) University of Technology Saeid Eslamian Isfahan University of Technology Mahdi Gheysari Isfahan University of Technology Alireza Gohari Isfahan University of Technology Saeid Soltani Kopai Isfahan University of Technology

Research Article

Keywords: K-means, Clustering Method, Regional Frequency Analysis, Probability Distribution Function, Growth 69 Curve, Karkheh Basin, L-moments, Drought indices

Posted Date: June 7th, 2021

DOI: https://doi.org/10.21203/rs.3.rs-555386/v1

License:   This work is licensed under a Creative Commons Attribution 4.0 International License. Read Full License

Page 1/8 Abstract

Drought is one of the natural disasters that causes a great damage to the human life and natural ecosystems. The main differences are in the gradual effect of drought over a relatively long period; impossibility of accurately determining time of the beginning and end of drought; and geographical extent of the associated effects. On the other hand, lack of a universally accepted defnition of drought has added to the complexity of this phenomenon. In the last decade, due to increasing frequency of drought in Iran and reduction of water resources, its consequences have become apparent and have caused problems for planners and managers. Therefore, in this study, to investigate severity and duration of meteorological, hydrological and agricultural drought in Karkheh River basin, regional frequency analysis of standardized precipitation index ( SPI ), standardized evapotranspiration index ( SEI ), standardized runoff index ( SRI ) and standardized soil moisture index ( SSI ) was performed using L- moments. Then, using Hosking and Wallis heterogeneity test, basin was divided into four homogeneous areas. After that, based on the Z statistic of goodness-of-ft test for each distribution, the best regional distribution function for each homogeneous region was selected. The results showed that hydrological drought occurs with a very short time delay in Karkheh River Basin after the meteorological drought and two indicators show meteorological and hydrological drought conditions well. Agricultural drought occurs after meteorological and hydrological drought, respectively, and its severity and duration are less than the other indicators. Meteorological, hydrological and agricultural droughts do not occur at the same time in all of the years and in general, the SPI drought Index shows the most severe droughts compared with the other three indices.

Full Text

This preprint is available for download as a PDF.

Figures

Page 2/8 Figure 1

Location of Karkheh River Basin in Iran Note: The designations employed and the presentation of the material on this map do not imply the expression of any opinion whatsoever on the part of Research Square concerning the legal status of any country, territory, city or area or of its authorities, or concerning the delimitation of its frontiers or boundaries. This map has been provided by the authors.

Page 3/8 Figure 2

Geographical location of stations in Karkheh River Basin Note: The designations employed and the presentation of the material on this map do not imply the expression of any opinion whatsoever on the part of Research Square concerning the legal status of any country, territory, city or area or of its authorities, or concerning the delimitation of its frontiers or boundaries. This map has been provided by the authors.

Figure 3

Trend of changes in the SPI, SEI, SRI and SSI drought indices during period 1996 to 2019 in Karkheh River Basin (Horizontal axis represents the time interval and vertical axis represents the monthly average regional values of indicators.)

Page 4/8 Figure 4

Estimation of severity and duration of Sthe PI, SEI, SRI and SSI drought indices in NourAbad station (Vertical axis shows amount of severity and duration of drought indicators and horizontal axis shows the changes in indicators over 1996-2019. Red: severe drought, yellow: moderate drought, green: normal years, and blue: wet season.)

Page 5/8 Figure 5

Position of stations in four areas according to K-Means clustering method (Between Sum of Squares / Total Sum of Squares = 70.9 %)

Page 6/8 Figure 6

L-moments ratio Diagram for duration of SPI drought index in four regions

Page 7/8 Figure 7

Growth curve

Page 8/8