International Research Journal of Engineering Science, Technology and Innovation (IRJESTI) Vol. 1(6) pp. 161-174, September 2012 Available online http://www.interesjournals.org/IRJESTI Copyright © 2012 International Research Journals Full Length Research Paper Statistical and trend analyses of rainfall in Sokoto Ismail 1 Abubakar and *Oke 2 Isaiah Adesola 1 Water Resources and Environmental Engineering Department, Ahmadu Bello University, Zaria, Nigeria. 2 Civil Engineering Department, Obafemi Awolowo University, Ile-Ife, Nigeria. Accepted September 18, 2012 Sokoto is in the North West geopolitical zone of Nigeria. The major occupation of the people in this city is farming, which depends on rainfalls. This article presents statistical and trend analyses of the rainfall in Sokoto. Rainfall data in the city for a period of 1915- 2008 were collected from archives. The existence of trend and sequence of rainfalls were established using non-parametric techniques. The study revealed that overall averages of yearly and monthly total rainfall were 726±24.03 mm and 61.75±25.31 mm respectively. Yearly total, mean, maximum and minimum rainfalls have Mann-Whitney of 42, 57, 67 and 37 between 1947and 1977 with 43, 66, 60 and 107 in the period between 1978 and 2008. Sen.’s estimator revealed that there are significant upward trends for yearly total (10.08mm/year), yearly mean (8.14 mm/year), maximum (6.84 mm/year) and minimum (10.72 mm/year) within a period of 1947 – 1977 and significant downward trends for yearly total (9.94mm/year), yearly mean (6.97 mm/year) and maximum (7.75 mm/year) within a period of 1978 – 2008. It was concluded that there is a significant downward trend in the yearly total and mean rainfalls at Sokoto in the last three decades (30years), which can be attributed to climate change. Keywords: Rainfall, Trend analysis, Statistical methods, Non-parametric techniques, upward trend. INTRODUCTION Climate change seems to be the foremost global challenge facing humans at the moment. The scientific community has not been left out as the causes and the solutions climate change. One of the indicators of climate change is increase or decrease in rainfall (Obot et al., 2010). Rainfall is a climate parameter that affects the way and manner man lives. It affects every facet of the ecological system, flora and fauna inclusive. Globally, lots of studies have been conducted on rainfall. Obot et al. (2010) presented total amount of rainfall across Nigeria in selected locations in each of the six geopolitical zones within a 30 years period (1978-2007) and the study reveals an increasing trend in only one out of the six *Corresponding Author E-mails: abuismail1@yahoo.com; okeia@oauife.edu.ng; aismail@abu.edu.ng locations. Abaje et al. (2010) worked on an analysis of rainfall trends in Kafanchan, Kaduna State, Nigeria. It was stated that government policies in Nigeria should be based on recent rainfall trends. Sokoto is in Sokoto state, which is in North West geopolitical zone of Nigeria. The state has a population 3,696,999; population density of 133 people per km 2 and catchment of 27,825 km 2 (Figure 1, Dada et al., 2007). The climate is semiarid with a zone of savannah-type vegetation as part of the sub-Saharan Sudan belt of West Africa. Farming is the major occupation in the place. It is well known that crop production in semi-arid regions is largely determined by climatic and soil factors. These show that a detailed knowledge of rainfall regime is an important prerequisite for agricultural planning and that there are needs to obtain the trend of rainfall in the entire region in Nigeria. The purpose of this study is to: characterize trend of total amount of rainfall in Sokoto and sequence of the rainfalls.