Determination of rainfall-recharge relationship in River Ona basin using soil moisture balance and water fluctuation methods

Abstract

A quantitative evaluation of spatial and temporal distribution of groundwater recharge is a prerequisite for the management of ground water resources system in an optimal manner. The amount of groundwater recharge depends upon the rate and duration of rainfall, as rainfall is the principal means for replenishment of moisture in the soil water system and recharge to ground water. This paper investigated the relationship between rainfalls and groundwater recharge within Ona River basin, southwest Nigeria, using soil moisture balance and water table fluctuation. Analysis of rainfall trends within the Ona River basin suggests that there is considerable high annual rainfall occurrence, with a mean of 1623.48. It must be noted that the mean annual lost due to evapotranspiration of 1361.68 mm is very high when compared to the rainfall (83.9%). The results obtained from the soil moisture balance when considering the three dominant soil types within the basin, that is, sandy loam, clay and find sand, having water capacity of root zone value of 70, 70, and 50 respectively, suggests that groundwater recharge follows a positive trend as the corresponding rainfalls. However, empirical relationships of: y = 0.540x-606.2, with a coefficient of determination (r 2) value of 0.719, for sandy loam and clay; and y = 0.552x-621, with a coefficient of determination (r 2) value of 0.726 for fine sand was established for the basin area. On the other hand, recharge ranging from 220.25 to 40.50 mm was computed from the water table fluctuation method.

Natural Groundwater Recharge Response to Climate Variability and Land Cover Change Perturbations in Basins with Contrasting Climate and Geology in Tanzania

“…Moreover, despite the dereference in climate and geology, groundwater recharge followed a positive trend as rainfall in the two study areas. This reiterates what was reported earlier on by Oke et al [19]. This study has also proven that decreasing rainfall contributes to decreasing groundwater recharge, as pointed out by other researchers [9].…”

“…Debatably, groundwater recharge is positively related to rainfall as decreasing precipitation is said to contribute more to decreasing groundwater table levels [9,19]. Nevertheless, this may not be scientifically true altogether as other factors come into play and the relation between rainfall and natural groundwater recharge may not be linear.…”

Flood risk management in Nigeria: a review of the challenges and opportunities

“…Ironically, residents of many Nigerian communities ravaged by flooding also lack access to potable water. For instance Adesogan [26] reported poor water supply coverage for nearly 22% across the South West region of Nigeria while Oke et al [27] noted there is a challenge of water sourcing within a major portion of this region. An integrated solution may be a rainwater harvesting system designed to meet water supply needs and also serving as an FRM scheme.…”

Climatic variability on groundwater recharge of Mymensingh district in Bangladesh

“…The study also revealed that an inverse relationship was observed between annual average humidity and GW recharge, whereas there was a direct relationship between rainfall and annual GW recharge over the study period. From the rainfall-recharge relationship in this study, it can be mentioned that the amount of GW recharge highly relies on the rate and duration of rainfall, as rainfall is the principal means for replenishment of moisture in the soil water system and recharge to ground water (Oke et al, 2014).…”