International Scholars Journals African Journal of Geography and Regional Planning ISSN 3627-8945 Vol. 5 (1), pp. 001-020, January, 2018. Available online at www.internationalscholarsjournals.org © International Scholars Journals Author(s) retain the copyright of this article. Full Length Research Paper Assessment of water balance indices in Nigeria over two years with contrasting moisture condition 1 Kehinde Musa Oladejo and 2 Aliyu Tambuwal Umar 1&2 Department of Geography, Usmanu Danfodiyo University, P.M.B. 2346, Sokoto, Nigeria. Accepted 26 December, 2017 A routine study of water balance is a veritable tool in monitoring the amount of water that will be available in the soil of any particular place at a particular time for optimal crop production and other uses. This study assessed water balance indices in Nigeria over two years with contrasting moisture condition. Mean monthly air temperature and monthly rainfall data for 1983 and 2003 were sourced from the archives of the Nigerian Meteorological Agency (NIMET) with respect to twenty-seven weather stations across Nigeria. The data were subjected to Thornwaite’s and Climatic water budgeting procedure to estimate water balance indices such as potential evapotranpiration, actual evapotranspiration, water deficit and water surplus. Paired sample test revealed that there is a significance difference between the water balance indices of a dry year and a wet year and across different locations in Nigeria [p=.000]. This study concluded that there is no uniformity in the pattern of water balance indices across Nigeria for over two years. It is recommended that more functional irrigation projects be established in those locations where water deficit is higher in order to boost their crop production throughout the year in Nigeria. Keywords: Water balance indices, actual evapotranpiration, potential evapotranspitraion, water deficit, water surplus. INTRODUCTION One of the important aspects of climatic study that has greatly been neglected in the realm of climate science is the water balance. This might be because water balance indices such as potential evapotranpiration, actual evapotranpiration, soil moisture storage, water deficit, water surplus and runoff are difficult to be determined in an area except through estimation approach. Water balance is an accounting of the inputs and outputs of water on the earth’s surface. The water balance of any place, whether it is an agricultural field, watershed, or continent, can be determined by calculating the input, output and storage changes of water on the earth’s surface. The major input is from precipitation and output is evapotranspiration (Ritter, 2012). Water balance is also Corresponding author's E-mail: muskad2008@yahoo.com; Tel. 08070782425 a simple accounting scheme used to predict soil-water storage, evapotranspiration, and water surplus. Similarly, water balance can be considered like a financial statement of income and expenditure, that is, an estimation of the quantity of water added, removed, or stored in the soil during a particular period (Seann, et al., 1997). This study focuses on the assessment of some water balance indices in Nigeria over two years with contrasting moisture condition. The year 1983 has been described as a dry year while 2003 has been described as a recovery year from the 1980s drought scenario in Nigeria (Umar, 2013). The aim of this study is to assess the spatial and temporal patterns of water balance indices in Nigeria over the two years with contrasting moisture condition. The objectives of this study are to: calculate the annual potential evapotranspiration for the wet and the dry years across twenty-seven different locations in Nigeria; compute water balance sheets for the twenty-seven selected