Abstract
Present paper tries to understand the influence of hydrogeological characteristics on groundwater yield of shallow wells in regolith aquifer, Ilorin, Nigeria. The data on hydrogeological characteristics such as drawdown, water level, depth of borehole, depth of overburden and well yield for 78 borewells were collected from Kwara State Ministry of Water Resources and Lower Niger River Basin Development Authority in Ilorin. While the aquifer transmissivity and well specific capacity was calculated from this data. The data obtained were subjected to Pearson moment correlation, multiple and stepwise multiple regression analysis. The results of the stepwise multiple regression (R 2 of .929) indicates that aquifer transmissivity and drawdown contributed 92.9% to the variability in well yield in the study area. It is concluded that while constructing wells, aquifer transmissivity and the rate of drawdown be taking into account for the purpose of having productive well in the study area. Keywords : Aquifer Transmissivity, Well Specific Capacity, Regolith Aquifer, Drawdown, Well Yield, Groundwater, Ilorin, Nigeria.
Highlights
Groundwater is considered as the world’s largest accessible store of freshwater, considered as a logical resource to turn to when confronted by water shortages which is often associated with low and variable river discharges (Goulden et al, 2009; Kundzewiez and Dou, 2009; Taylor et al, 2009)
The relationship between the well yield and hydrogeological characteristic is presented in table 4, and it shows that for every 1% increase in aquifer transmissivity, well specific capacity, well depth, drawdown and depth of overburden, there is 12.77%. 0.156%, 0.022%, 0.045% and 0.008% increase in well yield respectively
The relationship between the well yield and hydrogeological characteristic using stepwise multiple regression is presented in table 6, this shows that for every 1% increase in aquifer transmissivity and drawdown, there is 13.47% and 0.077% increase in borehole yield in the study area
Summary
Groundwater is considered as the world’s largest accessible store of freshwater, considered as a logical resource to turn to when confronted by water shortages which is often associated with low and variable river discharges (Goulden et al, 2009; Kundzewiez and Dou, 2009; Taylor et al, 2009). Groundwater is often of potable quality and does not require expensive treatments and permits scaled development (upon demand) using infrastructure that is normally of lower cost relative to surface water feed supplies (Taylor et al, 2009). Ilorin is underlain by Precambrian Basement Complex; comprising mostly of gneiss, granite, schist, undifferentiated meta-sediments rocks and overburden that are composed mainly of clay, sand and silt soils (Ifabiyi and Ashaolu, 2013). The aquifers of the Basement Complex rocks are the regolith and the fractures in the fresh bedrock (Bala et al, 2011). According to Wright (1992), the regolith aquifers occur more extensively in areas where a relatively thick and permeable saturated rock layers exist which is able to meet the demands
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