Document Type : Complete scientific research article
Authors
1
Department of Water Engineering, Faculty of Agriculture, Shahid Bahonar University of Kerman, Kerman 7616913439, Iran.
2
Institute of Hydro-Engineering, Polish Academy of Sciences, Gdansk 80-328, Poland.
3
Associate Professor. Department of Water Engineering, Faculty of Agriculture, Shahid Bahonar University of Kerman, Kerman 7616913439, Iran.
Abstract
Background and Objectives: River flow, one of the most influential factors affecting water resources and hydrological phenomena, interacts with climatic factors. Consequently, detecting changes in river discharge over time can reveal the presence or absence of climate change in a specific region. Previous studies have shown that river discharge varies owing to changes in hydrological patterns, human intervention, changes in vegetation, or annual climate fluctuations. The innovation of the current research lies in evaluating the discharge trend of the Halilrood River in the Hamon-e Jaz-Murian basin in Iran using wavelet transform, assessing its performance, and comparing it with the Mann-Kendall method.
Materials and Methods: In this study, wavelet transform was used to detect possible trends in the discharge flow of the Halilrood River, which is one of the most important rivers in south-eastern Iran. For this purpose, discharge data from the Hossein-Abad station, from 1963 to 2010, and the Kohank-Sheibani station, from 1982 to 2012, both located on the Halilrood River, were analyzed. Moreover, the results of the model were compared with the Mann-Kendall trend test.
Results: The monthly, seasonal, and annual trends at both stations showed consistent downward trends, indicating a decrease in the river discharge. Moreover, the trend detection results obtained using the wavelet transform, indicated a negative trend at all scales in the Hossein-Abad station, with a significance level of 0.001. The same result was observed at Kohank-Sheibani station. Both the Mann-Kendall and wavelet transform methods recognize the type of downward or upward trend well. For the annual trend analysis, both modes of the wavelet transform method outperformed the Mann-Kendall method, exhibiting higher values and greater significance across various significance levels. In the seasonal mode, the Mann-Kendall method outperformed the wavelet transform at the second level, but showed weaker performance at the first level. In the monthly analysis at the Kohank-Sheibani station, a basin outlet, the Mann-Kendall method's trend values show greater significance.
Conclusion: The wavelet transforms and the Mann-Kendall trend test was used to detect the possible trends in the discharge flow of the Halilrood River at the Hossein-Abad and the Kohank-Sheibani stations. In general, the results showed a decrease in discharge at this station on all timescales. Wavelet transform analysis revealed a significant downward trend in discharge at the Kohank-Sheibani station across monthly, seasonal, and annual scales, all at the 0.001 significance level. Overall, the results indicate a decrease in discharge at the stations across all scales throughout the periods.
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