Analysis of Rainfall Trends and Periodicity in Ruiru Location, Kenya
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Climate change is a serious issue in the world today with extreme weather conditions being experienced globally as characterised by devastating floods and prolonged droughts. This has often led to destruction of property and loss of life. These conditions are viewed as disasters requiring mitigation. Ruiru location being a peri-urban area has a lot of farming taking place and increased population due to settlement. This has increased the demand for water as stream flow is decreasing and boreholes are drying, with water scarcity prominent during droughts. Moreover during floods there is high surface runoff in the paved areas. The study sought to determine rainfall trends across the year for 31 years if any in Ruiru location. Monthly rainfall data for 31 years (1984-2014) obtained from four stations located within the location; Ting’ang’a, Ruiru mills, coffee research foundation and Doondu were used. Graphs were constructed to show trends within months and years and statistical significance of the observed trends tested using a linear regression model. Statistical analysis using Mann- Kendall, Spearman’s Rho, Linear Regression and Student’s t was employed to determine the significant difference among the four stations. High annual mean rainfall of 170mm and low annual mean rainfall of 37 mm were observed. Mann- Kendall, Spearman’s Rho, Linear Regression and Student’s t showed no significant difference of rainfall means between Ting’ang’a and Ruiru Mills stations, while the other stations were statistically insignificant. Linear regression models showed an upward trend which was statistically insignificant in all the four stations. There was no significant trend across the year for the past 31 years. The research findings will help in prediction of the occurrence of high and low rainfall amounts for proper planning and water resources management.