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Probability Analysis for One Day to Three Consecutive Days of Annual Maximum Rainfall: The Case of Gimbi Town, Oromia Region, Ethiopia

Received: 20 October 2025     Accepted: 30 October 2025     Published: 11 December 2025
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Abstract

Rainfall data frequency analysis and probability distribution enable future extreme events. Determining the magnitude of an extreme rainfall event for a given probability level is crucial for constructing irrigation and other hydraulic systems. On Earth, rainfall is a rare but significant hydrological characteristic. The analysis was for one to three consecutive days of maximum annual rainfall using a variety of widely used probability distributions. In order to determine the best-fit probability distribution, daily rainfall data for Gimbi Town were taken from 1995 to 2019 and gathered from the Ethiopian Meteorological Institute (EMI). The chi-square (χ²) test was used to measure the goodness of fit between the expected and observed values. The chi-square value of the 1, 2 and 3-day maximum annual daily rainfall was 8.8, 3.8, and 5.4 respectively. Chow method was the best-fit probability distribution for predicting the annual 1 and 2-day maximum rainfall for various return periods and the log-Pearson type-III distribution was the best-fit probability distribution for predicting the annual 3-day maximum rainfall for various return periods. The results of this study would be useful for agricultural scientists, decision-makers, policy planners, and researchers for agricultural development and construction of small soil and water conservation structures, irrigation, and drainage systems in Gimbi Town, Ethiopia.

Published in Science Futures (Volume 1, Issue 1)
DOI 10.11648/j.scif.20250101.19
Page(s) 70-83
Creative Commons

This is an Open Access article, distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution and reproduction in any medium or format, provided the original work is properly cited.

Copyright

Copyright © The Author(s), 2025. Published by Science Publishing Group

Keywords

Chi-square Test, Gimbi, Gumbel, Rainfall, Return Period, Probability Distribution

References
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  • APA Style

    Mosisa, G. (2025). Probability Analysis for One Day to Three Consecutive Days of Annual Maximum Rainfall: The Case of Gimbi Town, Oromia Region, Ethiopia. Science Futures, 1(1), 70-83. https://doi.org/10.11648/j.scif.20250101.19

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    ACS Style

    Mosisa, G. Probability Analysis for One Day to Three Consecutive Days of Annual Maximum Rainfall: The Case of Gimbi Town, Oromia Region, Ethiopia. Sci. Futures 2025, 1(1), 70-83. doi: 10.11648/j.scif.20250101.19

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    AMA Style

    Mosisa G. Probability Analysis for One Day to Three Consecutive Days of Annual Maximum Rainfall: The Case of Gimbi Town, Oromia Region, Ethiopia. Sci Futures. 2025;1(1):70-83. doi: 10.11648/j.scif.20250101.19

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  • @article{10.11648/j.scif.20250101.19,
      author = {Gemechu Mosisa},
      title = {Probability Analysis for One Day to Three Consecutive Days of Annual Maximum Rainfall: The Case of Gimbi Town, Oromia Region, Ethiopia},
      journal = {Science Futures},
      volume = {1},
      number = {1},
      pages = {70-83},
      doi = {10.11648/j.scif.20250101.19},
      url = {https://doi.org/10.11648/j.scif.20250101.19},
      eprint = {https://article.sciencepublishinggroup.com/pdf/10.11648.j.scif.20250101.19},
      abstract = {Rainfall data frequency analysis and probability distribution enable future extreme events. Determining the magnitude of an extreme rainfall event for a given probability level is crucial for constructing irrigation and other hydraulic systems. On Earth, rainfall is a rare but significant hydrological characteristic. The analysis was for one to three consecutive days of maximum annual rainfall using a variety of widely used probability distributions. In order to determine the best-fit probability distribution, daily rainfall data for Gimbi Town were taken from 1995 to 2019 and gathered from the Ethiopian Meteorological Institute (EMI). The chi-square (χ²) test was used to measure the goodness of fit between the expected and observed values. The chi-square value of the 1, 2 and 3-day maximum annual daily rainfall was 8.8, 3.8, and 5.4 respectively. Chow method was the best-fit probability distribution for predicting the annual 1 and 2-day maximum rainfall for various return periods and the log-Pearson type-III distribution was the best-fit probability distribution for predicting the annual 3-day maximum rainfall for various return periods. The results of this study would be useful for agricultural scientists, decision-makers, policy planners, and researchers for agricultural development and construction of small soil and water conservation structures, irrigation, and drainage systems in Gimbi Town, Ethiopia.},
     year = {2025}
    }
    

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    AU  - Gemechu Mosisa
    Y1  - 2025/12/11
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    N1  - https://doi.org/10.11648/j.scif.20250101.19
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    T2  - Science Futures
    JF  - Science Futures
    JO  - Science Futures
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    UR  - https://doi.org/10.11648/j.scif.20250101.19
    AB  - Rainfall data frequency analysis and probability distribution enable future extreme events. Determining the magnitude of an extreme rainfall event for a given probability level is crucial for constructing irrigation and other hydraulic systems. On Earth, rainfall is a rare but significant hydrological characteristic. The analysis was for one to three consecutive days of maximum annual rainfall using a variety of widely used probability distributions. In order to determine the best-fit probability distribution, daily rainfall data for Gimbi Town were taken from 1995 to 2019 and gathered from the Ethiopian Meteorological Institute (EMI). The chi-square (χ²) test was used to measure the goodness of fit between the expected and observed values. The chi-square value of the 1, 2 and 3-day maximum annual daily rainfall was 8.8, 3.8, and 5.4 respectively. Chow method was the best-fit probability distribution for predicting the annual 1 and 2-day maximum rainfall for various return periods and the log-Pearson type-III distribution was the best-fit probability distribution for predicting the annual 3-day maximum rainfall for various return periods. The results of this study would be useful for agricultural scientists, decision-makers, policy planners, and researchers for agricultural development and construction of small soil and water conservation structures, irrigation, and drainage systems in Gimbi Town, Ethiopia.
    VL  - 1
    IS  - 1
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