STRUCTURAL IMPACT ON AQUIFER HYDRAULIC PARAMETERS IN OKIGWE AND ENVIRONS, SOUTH EASTERN NIGERIA, USING INTEGRATED GEOPHYSICAL AND GIS PROCESSED REMOTE SENSING DATA

Abstract

An assessment of lineament impact on aquifer hydraulic parameters in Okigwe and Environs,

South Eastern Nigeria, using integrated geophysical and GIS processed remote sensing data was carried out to ascertain the effects of lineament on the resistivity, hydraulic conductivity, transmissivity and storativity of the aquifers in the study area. Okigwe and Environs are in a complex geological setting of Imo State within the Imo River Basin and lies between latitude 5^o35'N to 5^o56'N and longitude 7^o03'E to 7^o38'E. The litho-stratigraphic units within the study area are Ajali Formation, Nsukka Formation, Imo Formation, Ameki Formation and Benin Formation. A total of 84 vertical electrical soundings (VES) using the ABEM terrameter (SAS) 4000 was acquired in the study area applying the Schlumberger electrode configuration and a maximum electrode spacing of 1000m. Out of the eighty-four sounding stations, seventeen soundings (parametric soundings) were made at the vicinity of existing boreholes for comparative analysis and for quality control of the data. The trend surface analysis in relation with the lineaments results within the study area show that the dominant structural trend is in the NE-SW direction corresponding to the major lineament trend of the Anambra basin. The lineament interpretation from LANDSAT data revealed that the Nsukka Formation is characterized by a high lineament density. The study revealed structural influence on the resistivity, hydraulic conductivity, transmissivity and storativity of the aquifers in the study area. The findings from the study also revealed that the Nsukka Formation could be a good target for groundwater exploration. The directional relationship between the drainage pattern and the lineaments could imply that the drainage of the study area is structurally controlled. The integration of geophysical and GIS processed remote sensing data can be highly effective to assessing the impact of lineaments on the aquifer hydraulic parameters. Drilling through the Nsukka Formation should be done with caution to avert or forestall loss of circulation due to suspected faults.