Successful management of coastal groundwater resources depends not only upon planning and regulations. It also depends on accurate assessment and prediction of the behavior of saltwater interface to both natural conditions and man’s activities. Over the years, a combination of factors has resulted in changes in depth-to-saltwater (salinity depths) in the coastal aquifers of Niger Delta. In an effort to study the dynamics of salt/freshwater interface and estimate the current salinity depths in the Niger delta, down-the-hole geophysical logs (resistivity, spontaneous potential and gamma ray logs) were carried out in deep water-supply boreholes in the coastal parts of the Niger delta.The boreholes were drilled to depths ranging from 180m to 600m below ground level and completed into the Benin Formation, Pliocene-Recent in age. The logs clearly reveal the sub-surface stratigraphic successions, isolated saline-water contaminated stretches of the drilled holes and fresh water bearing layersin the area. Generally speaking, a good stretch of the drilled depth is contaminated by saline water to various depths. Water well drilling contractors can now be guided on the best section of the drilled column to place the screens to exploit fresh water from the boreholes.Proper borehole completion methods can also be adopted especially when the freshwater aquifer underlies a saltwater aquifer. Prior to this study, huge amounts of money had been wasted in drilling and completing boreholes which yielded saline water either from the onset or soon after being commissioned.
