21st Century Trend of Water Yield in River Basins of Guinea and Sudano-Sahelian Ecological Zones, Nigeria

Abstract

In Nigeria, the climate in recent years has witnessed significant variability across the various ecological zones due to climate change. Thus, the objective of this study was to analyse the 21st century trend of water yield in river basins of Guinea and Sudano-Sahelian ecological zones, Nigeria. The data and computation were done using KNMI Climate Explorer. The coordinates of the basins were used to derive the annual and seasonal water yield. Projections were produced for near-term (2019-2048), mid-term (2049-2078) and long-term (2079-2100) using ensemble mean of CMIP5 under RCP2.6, RCP4.5 and RCP8.5. Findings revealed that water yield during dry season demonstrates decreasing range of (-0.05 to-0.1 mm/day). It was observed that the decrease were only significant for RCP8.5 but not under middle and low emission trajectories. As for wet season, it reveals significant increasing trends at 0.05 significant levels with respect to RCP8.5 but not significant in low and middle emission scenarios. Regional trend analysis of average annual water yields reveals no significant positive trends for all the RCPs. This is to say that despite the projected increasing pattern of average annual water yield observed over Guinea and Sudano-Sahelian ecological zones, incidences of water crisis cannot be ruled out. Contribution/Originality: This paper's primary contribution is finding that river basins of Guinea and Sudano-Sahelian ecological zones of Nigeria will be significantly affected by the anthropogenic climate change at highest emission trajectory. The result can act as guidelines for strategic planning against water crisis as envisaged by the projection. 1. INTRODUCTION Climate projection is usually a statement about the likelihood that something will happen several decades to centuries in the future if certain influential conditions develop. Scenarios however, represent alternative possible ways in which the future may unfold [1]. Globally, it is estimated that by 2050 between 150 and 200 million people could be displaced as a consequence of phenomena, such as sea level rise and increased extreme weather events [2-5]. Furthermore, the Global Environmental Outlook's Baseline Scenario OECD, (2012) cited in Adefisan [6] projects increasing strains on water resources through 2050, with an additional 2.3 billion people expected to be living in areas with severe water stress, especially in North and South Africa and South and Central Asia. WWAP (United Nations World Water Assessment Programme) [7] predicts the world could face a 40% global water deficit by 2030 under a business-as-usual (BAU) scenario. Africa's rising population is driving demand for water under