Modeling of hydrogeological parameters and aquifer vulnerability assessment for groundwater resource potentiality prediction at Ita Ogbolu, Southwestern Nigeria

• Published in: Modeling earth systems and environment 2023-03, Vol.9 (1), p.749-769
• Main Author: Falowo, Olumuyiwa Olusola
• Format: Article
• Language: English
• Subjects: Chemistry and Earth Sciences; Computer Science; Earth and Environmental Science; Earth Sciences; Earth System Sciences; Ecosystems; Environment; Math. Appl. in Environmental Science; Mathematical Applications in the Physical Sciences; Original Article; Physics; Statistics for Engineering
• ISSN: 2363-6203; 2363-6211
• DOI: 10.1007/s40808-022-01490-8

Groundwater prospects and vulnerability mapping to vertical contamination, utilizing multi-criteria evaluation techniques and analytical hierarchy process were carried out within five geologic units in Ita-Ogbolu, southwestern Nigeria, comprising older granite (OGu), migmatite (M), charnockite (Ch), medium to coarse grained biotite granite (OGe), and coarse to porphyritic biotite hornblende granite (OGp). Seventy one electrical soundings involving Schlumberger array with 65 m electrode spread; in-situ (hydraulic) pumping tests; and hydrogeological parameter measurements from fifty one wells were used to acquire the hydrogeological data. The vulnerability evaluation was done using geoelectrical parameters obtained from longitudinal conductance (LC); and the aquifer vulnerability index (AVI), while the groundwater potential index value modeling (GWPIV) was used develop the groundwater potential map. All parameters measured were weighted, rated and assessed according to their significance to groundwater accumulation. The major aquifer unit was the weathered layer, having a 301 Ω m average resistivity, thickness of 14.1 m, 0.67 m/d hydraulic conductivity ( K ), and 9.82 m 2 /d transmissivity. The average depth of the overburden is 19.6 m, which is a moderate depth for groundwater accumulation. In addition, weak positive coefficients model between K and formation factor were found for all rock units. The relationship or correlation model of hydraulic conductivity ( K ) and formation factor ( F m) gives OGp (0.6005e −0.018x ), M (0.4601e 0.0695x ), Ch (0.0838e −0.0673x ), OGu (1.1623e −0.091x ), and OGe (0.5937e 0.0578x ). The relationship shows weak positive (