PLATFORM - A Journal of Engineering 12 PLATFORM VOLUME 5 NUMBER 4 2021 e-ISSN: 26369877 INTRODUCTION Hydrological analysis and Water resources development largely depend on hydrological and meteorological data. To achieve reliable and quality results for practical applications, such data should be free from outliers, homogeneous, and consistent to carry out frequency analyses or simulate a hydrological system [1]-[2]. Long-term precipitation data may be suffered from non-climatic factors that result in inhomogeneity of historical records. The non-climatic factors that caused the variations of long-term time records are the location of the stations, instruments, formulae used to calculate the mean, observing practices, and the station environment [3]. There are two ways to ensure homogeneity of data records; direct and indirect methods [4]. The direct methods of homogenisation involve best management practices in data recording and documentation. Indirect methods involve metadata analysis, creation of reference series, statistical tests for breakpoint detection, and adjustment of the data records [4]. To identify the effects of non−climatic factors in the observations over time, homogeneity tests are performed on time series data [5]. The homogeneity tests are of two types; absolute methods and comparative methods. In absolute homogeneity tests, each station is considered separately without considering the e ff ect of neighbouring stations. In relative homogeneity tests, neighboring reference stations are considered. This research used absolute methods. Several researchers have either assumed the data to be homogeneous or used absolute homogeneity tests alone in their research [6]. Received: 7 March 2021, Accepted: 2 June 2021, Published: 31 December 2021, Publisher: UTP Press, Creative Commons: CC BY-NC-ND 4.0 OUTLIER AND HOMOGENEITY ANALYSIS OF EXTREME RAINFALL SERIES IN KANO, NIGERIA Abdulrasheed Mohammed 1* , Salisu Dan’Azumi 1 , Abubakar Ahmed Modibbo 2 1 Department of Civil Engineering, Bayero University, Kano, Nigeria 2 Department of Civil Engineering, University of Maiduguri, Borno, Nigeria * Email: abdulrasheeddoko@gmail.com ABSTRACT Data preparation is one of the most important steps in the field of hydrology since the results of any research depend on whether the input data were reliable and rightly collected or not. Reliability and quality of long-term rainfall data are required before carrying out any study in hydrology. For this reason, outlier identification techniques and homogeneity tests have proved helpful. This study aimed at carrying out outliers and homogeneity analysis of extreme rainfall data series for the Kano rainfall gauging station. XLSTAT, 2019 was used to identify outliers through Grubb’s test for outliers/two-tailed test and Dixon test for outliers/two-tailed statistic test and Standard Normal Homogeneity Test (SNHT), Buishand Range (BR) Test, Pettitt Test, and Von Neumann Ratio (VNR) Test were used for homogeneity analysis. Four outliers were identified and treated accordingly. The results of homogeneity tests showed that the maximum daily rainfall data of the Kano gauging station is homogenous and classified as useful. The maximum daily rainfall data of Kano station can be used for any study in water resources and environmental engineerings, such as in Development of Intensity Duration Frequency (IDF) Curves and Rainfall- Runoff Simulations. Keywords: Outliers test, homogeneity tests, rainfall data, XLSTAT 2019