A quantitative evaluation of spatial and temporal distribution of groundwater recharge is a pre-requisite\r\nfor the management of ground water resources system in an optimal manner. The amount of\r\ngroundwater recharge depends upon the rate and duration of rainfall, as rainfall is the principal means\r\nfor replenishment of moisture in the soil water system and recharge to ground water. This paper\r\ninvestigated the relationship between rainfalls and groundwater recharge within Ona River basin,\r\nsouthwest Nigeria, using soil moisture balance and water table fluctuation. Analysis of rainfall trends\r\nwithin the Ona River basin suggests that there is considerable high annual rainfall occurrence, with a\r\nmean of 1623.48. It must be noted that the mean annual lost due to evapotranspiration of 1361.68 mm is\r\nvery high when compared to the rainfall (83.9%). The results obtained from the soil moisture balance\r\nwhen considering the three dominant soil types within the basin, that is, sandy loam, clay and find\r\nsand, having water capacity of root zone value of 70, 70, and 50 respectively, suggests that\r\ngroundwater recharge follows a positive trend as the corresponding rainfalls. However, empirical\r\nrelationships of: y = 0.540x ââ?¬â?? 606.2, with a coefficient of determination (r2) value of 0.719, for sandy loam\r\nand clay; and y = 0.552x ââ?¬â?? 621, with a coefficient of determination (r2) value of 0.726 for fine sand was\r\nestablished for the basin area. On the other hand, recharge ranging from 220.25 to 40.50 mm was\r\ncomputed from the water table fluctuation method.
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