Analysis of Hydro-Meteorological Variables and Runoff Characteristics in the Sudano-Sahelian Ecological Zone of Nigeria

Abstract

This study examines the impact of climate change on hydrologic resources of selected rivers and lakes in the Sudano-Sahelian Ecological Zone of Nigeria. Climatologically data acquired were rainfall, temperature and evaporation from Nigeria Meteorological Agency, Oshodi, Lagos. Similarly, the hydrological data of river discharge and lake levels were obtained from Nigeria Hydrological Services, Kaduna. We used the Standardised Anomaly Index to test for fluctuations in rainfall, temperature, runoff and water level in lakes. Mann Kendall statistics were used to examine the trends in the climate variables. Pearman correlation was adopted to test the relationship between runoff and the rainfall variables. The findings revealed a general downward trend in rainfall amounts in the 1970s and 1980s. The findings also detected an upward trend in the amount of rainfall from 1990 to 2019. The correlation results of rainfall attributes and runoff showed significant relationships in annual rainfall (r= 0.61), annual rain-days (r=0.61), rain days of heavy rainfall (r= 0.57) and wet season rainfall (r=0.54). These attributed when combined, revealed a 51% contribution to the overall regression with (r=0.51) at 95% probability level. The study concluded that the Sudano-Sahelian Ecological Zone of Nigeria experiencing an increase in the annual rainfall. The increase in rainfall point to the recovery of the rainfall from the great Sahelian drought of the 1970s and 1980s. The rise in the annual rainfall is a possible influencing factor to the frequent occurrences of flooding in recent time across the ecological zone.