Abstract
Boreholes have become a major source of water supply in South Eastern Nigeria, an area with diversity in geology, topography and climatic conditions. The common approaches in borehole investigations are surface survey and logging. The two approaches are supposed to be complementary. However, for small schemes of groundwater development, logging is hardly considered.. Six boreholes were selected from locations at the three geographical zones of Imo state. The selected locations are Umueze, Umuduru, Ogbor-Ugiiri, Ngor Okpuala and Eziama. Geophysical survey and logging were carried out. Electrical resistivity method was adapted for geophysical survey. ABEM Terrameter (SAS) 300B with digital read-out was used for logging. The degree of correlation between the variables was determined by computing the coefficient of correlation denoted as R<sup>2</sup>. The results indicate generally poor correlations between logging and geophysical surface values for the selected boreholes except for the one located at Ngor Okpala with R<sup>2</sup> value of 0.7408. At this location, geophysical surface method for borehole locations can be carried without any Logging exercise to establish the Total Drilling Depth (TDD). This will help reduce the total cost for the drilling of the boreholes and also save time and much desired energy. In those areas where no correlation exists, there is need for Government Financial support in drilling sustainable borehloes as much costs are involved in investigation and construction works.
Highlights
Groundwater is subsurface water that fill voids in soils and permeable, geological formation or groups of formations with yield water in sufficient quantity to be of consequence source of supply is called aquifer
Nigeria has abundant groundwater resources which have been developed through shallow dug wells and boreholes. 60% of Nigerians depend upon groundwater for their water supply be it for domestic, industrial or agricultural use
Since 1980, there has been astronomical increase in the number of boreholes constructed in Nigeria by the Government, communities, individuals and Non-governmental organizations assisted by international organizations such as UNICEF, UNDP, EU, FAO and World Bank
Summary
Groundwater is subsurface water that fill voids in soils and permeable, geological formation or groups of formations with yield water in sufficient quantity to be of consequence source of supply is called aquifer. Groundwater accounts for over 95% of the earth’s unable fresh water resources. It is uniquely suited as drinking water and it is widely disturbed. Nigeria has abundant groundwater resources which have been developed through shallow dug wells and boreholes. Investigations and exploration contribute substantially to the cost of groundwater as a source of water supply. The common approaches in investigation are the surface survey and logging. Geologic measurements in boreholes provide useful information about surface aquifer but the heterogeneity of some prospective zones of the aquifer pose the real challenge in conventional well logging. Borehole geophysical logging is a common technique in the characterization of aquifers are difficult to describe using data obtained in a limited number of boreholes. The main objective was to establish a standard and sustainable basis for proper borehole locations and design in the various zones
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