International Journal of Scientific Research and Engineering Development

International Journal of Scientific Research and Engineering Development

( International Peer Reviewed Open Access Journal ) ISSN [ Online ] : 2581 - 7175

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Investigation of the Variation of Annual and Seasonal Rainfall Patterns in Rathnapura District, Sri Lanka

    International Journal of Scientific Research and Engineering Development (IJSRED)

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Published Issue : Volume-4 Issue-1
Year of Publication : 2021
Unique Identification Number : IJSRED-V4I1P118
Authors : K.P.Jayasinghe, N.R.A.M.Ruwangika, G.M.L.P.Aponsu, W.M.A.Tharinda
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Abstract :

Rathnapura District is located in the south-western part of Sri Lanka and the wet zone. The district receives rainfall mainly from May to September due to the southwest monsoon winds and significant rainfall during the rest of the year due to convective rains. The annual average rainfall in the district is between 4,000 and 5,000 mm and the annual average temperature varies in the range of 24- 35 C. High humidity levels can be seen and the city is located 21 m above sea level. The main objective of this study was to identify the spatial distribution of annual and seasonal rainfall in the Rathnapura District by analysing the Rathnapura (1989-2018) long term and (2005-2019) short term data. Here, 14 meteorological stations in the area were analysed using short-term (15 years) and long-term (30 years) rainfall reports. Asymmetric tests, including the Mann-Kendell test, the sequential Mann-Kendell test, the linear regression analysis, and the continuous wavelength evolution test, were used to identify these possible precipitation trends. Rainfall tendencies were estimated using the linear regression model. According to the analysis, the highest annual average rainfall (352.86 mm) was recorded in the Alupolla group in terms of long-term data, while the lowest was recorded in the Balangoda post office (180.43 mm). Hapugasthenna recorded the highest annual average rainfall (327.75 mm) and Balangoda (166.47 mm) recorded the lowest annual rainfall. In considering the long-term rainfall analysis, an increasing trend has been identified by the second inter monsoon and annual rainfall data for the Balangoda Post Office. Short-term rainfall analysis shows an increasing trend for Pelmadulla and Kahawattacentres. Analysis of SQMK test shows a positive trend in annual rainfall of Pelmadulla. And the negative rainfall trend has was shown in the Balangoda during the first inter monsoon period and the negative precipitation of Rathnapura from during the second inter monsoon. In these 14 long-term and short-term rain gauges, at least four different patterns can be identified at all locations as a whole. That is, this can be considered as some information about the temporary variation in the Rathnapura district. However, cyclical patterns of precipitation can be easily identified by CW analysis.