Abstract
Identifying rainfall trends in highly urbanized area is extremely important for various planning and implementation activities, including designing, maintaining and controlling of water distribution networks and sewer networks and mitigating flood damages. However, different available methods in trend analysis may produce comparable and contrasting results. Therefore, this paper presents an attempt in comparing some of the trend analysis methods using one of the highly urbanized areas in Sri Lanka, Colombo. Recorded rainfall data for 10 gauging stations for 30 years were tested using the MannKendall test, Sen’s slope estimator, Spearman’s rho test, and innovative graphical method. Results showcased comparable findings among three trend identification methods. Even though the graphical method is easier, it is advised to use it with a proper statistical method due to its identification difficulties when the data scatter has some outliers. Nevertheless, it was found herein that Colombo is under a downward rainfall trend in the month of July where the area receives its major rainfall events. In addition, the area has several upward rainfall trends over the minor seasons and in the annual scale. Therefore, the water management activities in the area have to be revisited for a sustainable use of water resources.
Highlights
Climate change is a multidimensional phenomenon, which adversely impacts many social, environmental, and economic aspects [1]
Erefore, the aim of this paper is to analyze and compare the instrumental rainfall data in Colombo district obtained from historical weather records. is is timely important, being the capital of the country, Colombo is under many issues related to climate, natural disasters, and urbanization. e comparative analysis was carried to several rainfall scales varying on monthly, seasonal, and annual basis. e Mann–Kendall test, one of the long-established trend analysis test methods, Spearman’s rho test, which is a rankbased nonparametric method, and the graphical method in rainfall trend analysis have been used as trend analyzing methods in this analysis. e results obtained from each method were compared to have a clear idea on the accuracy of applying them for the analysis
Little difference can be observed from MannKendall test (MK) test to s Rho test (SR) test with no trends for Dehiwala and Padukka station at 1% significance level
Summary
Climate change is a multidimensional phenomenon, which adversely impacts many social, environmental, and economic aspects [1]. It has been revealed that there is a clear relationship between biological systems to the ongoing climate change. Decreasing precipitation trends are observed in some of the areas and in Sahel [4], the Mediterranean, southern Africa, and southern Asia [5]. Due to these climate changes and variations, frequent extreme climatic disasters, such as flood and droughts, have occurred. Ey have resulted in severe adverse impacts on infrastructure, dams, urban drainage systems, and livelihood of human, animals, and vegetation [6, 7]. Due to inability of predicting the climate patterns, the flood defenses have become less efficient
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