The use of statistical grain-size method in analysing borehole and evaluating aquifer parameters. A case study of Ajali Sandstone formation, southeastern Nigeria

Abstract

Several challenges abound with the accurate estimation of aquifer parameters in Groundwater resource development. This paper describes the investigation on the aquifer (mainly Ajali Sandstone Formation) parameters in Nsukka area. The Ajali Sandstone Formation is among the principal sources of groundwater in the area. (9) boreholes drilled in the area were analysed texturally using statistical grain size method.Results show that the highly permeable members of Ajali Sandstone are devoid of surface waters and are seen to be friable, medium-grained, poorly sorted, and highly cross-bedded. Recharge is mainly through rainfall. The distribution of major geological units, well log data, static water level data, and surface features were found to have influenced groundwater occurrence and flow pattern in the study area. The lithological logs showed sandy aquifers separated by clayey aquitards, while stratigraphic analyses of well lithological logs revealed the presence of at least four layers of contrasting hydraulic conductivity, making the aquiferous Ajali Sandstone homogenous and anisotropic. Values of permeability (k) from 0.00753 to 0.01512 cm 2 , hydraulic conductivity (K) from 8.2886 to 16.6444 m/s, transmissivity (T) between 455.87 and 1002.48m 2 s -1 , and specific yield from 2.35 to 4.76m 3 were found to be consistently high, thus suggesting thick and prolific aquiferous zones.

Lithological and Structural Characterization of parts of the Lower Benue Trough, Southeast Nigeria, Using Radiometric and Aeromagnetic Data

“…Previous studies suggest that the basin originated as a 'pull-apart' structure associated with the opening of the Atlantic Ocean and the extensive rifting of the Central and West African basement uplift which ended in Early Tertiary with the development of the Tertiary Niger Delta [5][6][7] . The sedimentary fill of the basin is characterized by magmatic activities as evidenced by the widespread occurrence of geologic structures and basic and intermediate intrusive and extrusive rocks 8 . This study was carried out from January to December, 2020.…”

Hydrogeophysical Investigation and Aquifer Evaluation of the Formations in Nsukka Area, Southeastern Nigeria

“…Both were run in uncased condition. The static water level, hydraulic conductivity (K), transmissivity (T) and discharge (Q) were calculated following methods described by Ezim et al (2017), Harleman, et al (1963, Hazen (1983), Henriet (1976), Uma, et al (1989.…”

Reassessing Groundwater Potentials and Subsurface water Hydrochemistry in a Tropical Anambra Basin, Southeastern Nigeria

“…The formation thins southward to a few tens of meters around Okigwe. Studies have shown that the higher section of the Ajali Formation is ferruginized in some areas [54,64,[66][67][68][69] . This condition, joint with the clay/shale unit of the overlying Nsukka Formation and the basal Mamu Formation favors the progression of a confined/semi-confined aquifer system [54] .…”