Electrical resistivity method (Seismic reflection method)
Effieotor, (1989), employed vertical electrical sounding (VES) in the determination of portable ground water in the Eastern Niger Delta.
As observed that the result of electrical resistivity methods of survey revealed fresh water zone which was not sharply delineated from the underlying salt water because of the consolidated zone of salt water arising from intermixing of the two horizons.
Electrical resistivity method
Electrical resistivity method has been extensively used to resolve the hydrological problems. Issar and Levanon (1974) applied this technique to map the top of limestone and dolomite aquifers in the foot hills of Israel. Arafin and Lee (1985) successfully carried out vertical electrical soundings using Schlumberger configuration to delineate depth to bedrock. Cornwell and Carruthers (1986) used electrical resistivity sounding in conjunction with seismic refraction to determine thickness of a channel fill in the Chalk bedrock of East Angola. They found that thickness of the channel filled deposit was up to 100 meters. Reynolds (1987) also used electrical resistivity method to demarcate the thickness of an aquifer under a rural water supply project of southern Kano state, Nigeria.
Seismic reflection method
To delineate near-surface geological and geotechnical features, Prado et al. (2001) conducted seismic survey in Sao Paulo sedimentary basin, Brazil using a common midpoint geometry. They delineated clay and sand layers in the alluvium and reported bedrock as gneiss. Stephenson et al. (2002) carried out shallow seismic reflection investigations in the vicinity of Galena city, Alaska and reported depth to bedrock greater than 550 feet. Hamzah et al. (2003) also applied seismic reflection method for the investigation of subsurface structures in Banting, Pahang delta and Sarawak areas of Malaysia. Depth to base of the aquifer was estimated in the range of 75 to 200 meters. In Pahang area about 100 meters deep and 150 meters wide river channel was detected. In Sarawak area they reported a fault controlled sinkhole of about 20 meters in diameter at a depth varying between 10-15 meters.
Francese et al. (2005) conducted high resolution seismic reflection survey in the area of Lambro Park of Milan city to image the geometry (structure and stratigraphy) of the shallow aquifer in Pleistocene and Holocene deposits. Results obtained showed that it was a multilayer aquifer system. Likewise Deidda et al. (2006) successfully mapped Palaeozoic bedrock topography and stratigraphy of fluvial sediments of the Flumendosa River delta, Italy by using seismic reflection data.
In very recent study Kim and Kim (2008) made use of seismic reflection data to characterize an aquifer in Korea. They reported that top of bedrock actually constituted the lower boundary of the alluvial aquifer and depth to bedrock ranged between 30 to 46 meters. Larson and Stevens (2008) used seismic reflection data successfully to differentiate the Precambrian crystalline bedrock from the overlying glacial, marine, glacimarine and channel fill deposits along the west coast of Sweden. De France et al. (2009) conducted reflection surveys to define the structures of sediments filled valleys in Italy and demarcated morphology of the bedrock.