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Homogeneity Testing and Trends Analysis in Long Term Rainfall Data for Sungai Pahang River Basin Over 40 Years Records

Author(s): Chun Kiat Chang, Aminuddin Ab. Ghani, How Tion Puay, Mazlina Alang Othman

Linked Author(s): Chun Kiat Chang

Keywords: Homogeneity test; trend analysis, IDF curves, rainfall extreme, Sungai Pahang river basin

Abstract: Current design of infrastructure is primarily based on precipitation Intensity-Duration-Frequency (IDF) curves. For this reason, the accuracy and reliability of the hydrological analysis relied on the quality of the rainfall data used. Rainfall data should be checked and tested for its reliability and homogeneity before being used for further analysis. However, factors such as location of the station, the tool and method of data recording, collection and observation quality will affect the homogeneity of rainfall records. For that reason, a subsample of 9 stations that have more than 40 years of observations obtained from the Department of Irrigation and Drainage (DID) Malaysia located in Sungai Pahang river basin are investigated for homogeneity by using four absolute homogeneity tests. These include the Standard Normal Homogeneity test (SNHT), Pettitt test, Buishand Range test (BRT), and Von Neumann ratio (VNR) test. The result of each method was evaluated at the 95% significance level. The annual rainfall amount was used as testing variable and the results from four tests were then combined into three classes: �useful�, �doubtful� and �suspect'. Among all rainfall stations within the river basin, there are only 1 station (Kg Merting, ID = 4223115) was inhomogeneous (labeled as �suspect�), whilst remaining 8 of rainfall stations are homogeneous and considered as �useful�. From the analysis of trends, only 2 of the stations (Rumah Pam Pahang Tua, ID = 3533102 and Kg Merting, ID = 4223115) indicate statistically increasing trend. Inhomogeneity of rainfall data at station Kg Merting may correspond to the result of statistically increasing trend in that station. The findings of the study will be useful for planning and designing infrastructure in managing floods, as well as flood risk and infrastructure systems failure risk in Sungai Pahang river basin


Year: 2017

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