Historical fluctuations in hydroclimatic variables can reveal important information about water resource changes in any basin. The innovative polygon trend analysis (IPTA) method was used to analyze 45-year rainfall data from eight monitoring stations in the Mae Klong River Basin, Thailand. The IPTA graphics were developed for the mean monthly rainfall and the standard deviation of the monthly rainfall for each station. In addition, the IPTA results were compared with the Mann–Kendall (MK) test and the Sen's slope method. The IPTA graphics showed no regular polygon for any rainfall station, which indicated variability of rainfall over the years. The IPTA method showed increasing trends for the month of April while decreasing trends in the month of October for the majority of the stations (7 of 8). A good agreement for detection of trends was found between the IPTA method and the MK test. Both the methods found trends (increasing/decreasing) for 69 months (72%) and showed no trend for 27 months (28%) out of a total of 96 months. The findings of this study could benefit water supply and management, drought monitoring, and agricultural production activities in the Mae Klong River Basin in the future.

  • Application of innovative polygon trend analysis for monthly rainfall in the Mae Klong River Basin, Thailand.

  • Trend length and trend slopes are calculated.

  • A comparison is made between the innovative polygon analysis method and the nonparametric tests: the Mann–Kendall test and the Sen's slope method.

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