Author(s): Ayuko Hirani Saleh; Akira Tai; Mukhsan Putra Hatta; Shinichiro Yano

Linked Author(s): Ayuko Hirani Saleh, Akira Tai, Shinichiro Yano

Keywords: Climate change; Rainfall variability; Trends; Jeneberang river basin

Abstract: An in-depth understanding of the erratic rainfall patterns in a watershed due to the negative impacts of climate change is crucial to understand the hydrological cycle in a watershed. The main objective of this study is to better understand rainfall trends using statistical tools in the Jeneberang River basin, South Sulawesi, Indonesia. At present, there is still no research on the distribution of precipitation trends in the area. This study examined general rainfall data for 23 years (1996-2019) and collected from three rainfall stations. The nonparametric Mann-Kendall and Sen Slope estimator statistical tests were performed to identify whether there was a positive or negative trend in the rainfall data with statistical significance. Results showed an increasing trend in the monthly rainfall data only in both rainfall stations. The Alukeke station had a minimum rainfall of zero millimeters in May, June, and July, while other months, which included January and December, had a minimum of over a hundred millimeters respectively. Monthly rainfall data for the Alukeke rainfall station revealed that there was no significant trend detected in ten months, but May and June indicated a significant trend. This result proved an increasing trend in the data series, though insignificant for the Sen-slope’s test. Similarly, the Malino station had a minimum rainfall of 0 mm, while the highest amount of rainfall of 1518 mm was recorded in December. The p-value for June in the Malino rainfall station was the only one with a significant level of α < 0.05, thereby signifying a trend in the data series. The overall p-value of 6.041 was, however, well above the significant level of α of 0.05, thus indicated that there was no significant trend detected in the data series. The Sen slope estimator indicated a decreasing trend in February, October, and December, unlike a significantly positive trend in the other eight months of the seasons. The results of the p-value in the Paladingan rainfall station detected an insignificant trend in the data series, while the Paladingan station recorded a maximum of 1435 mm in December. The sen-slope statistic showed no change in four months of the year as well as a decreasing trend in the other five months. In contrast, three months had positive changes, with 1.951 for May, 1.038 for June, and 0.343 for July. Thus, the overall Sen Slope tests of -33.513 indicated that there was a slight decrease in the data series. The novelty of this research lies in the theory of value in the analysis of extreme rainfall in the data-scarce Jeneberang watershed. The results are useful for water resources management and disaster risk reduction functions in this watershed.

DOI: https://doi.org/10.3850/IAHR-39WC252171192022842

Year: 2022