Electromagnetic (EM) profi ling and Vertical Electrical Sounding (VES) studies were carried out for groundwater exploration in the Twifo-Hemang Lower Denkyira Districts of Ghana. These two geophysical methods were used for exploring the groundwater potentials beneath Achiase Community, Mbaa Mpe Hia Community and Moseaso Community. This paper seeks to encourage the use of inversion for interpreting electromagnetic data rather than the usual qualitative interpretation method using line graphs and also the use of apparent resistivity maps as 2D pseudo resistivity maps to support interpretations of the 1D inversion results (in cases where the available budget could not permit 2D and or 3D inversion). These would help in enhancement of obtained results, reduce ambiguity and help decision making. The EM results revealed that; the three communities are underlain by two layers with the fi rst layer having the thickness range between 2 to 10 m and the second layer is a half space. The results from VES studies indicate that; Achiase Community and Mbaa Mpe Hia No. 2 community are underlain by three geoelectrical layers and Moseaso Community is underlain by four geoelectrical layers. On the basis of this study the Moseaso Community is ranked highest in terms of groundwater potential followed by the Achiase community and fi nally the Mbaa Mpe Hia No.2 Community. Several sites were recommended for drilling boreholes for water supply in these communities.
2D seismic refraction data, from seven traverse lines, were used to investigate subsurface geology in the Appollonian Formation of the onshore Tano Basin of Ghana. Tano Basin is one of the four basins of Ghana and the most important one when it comes to oil potential of Ghana. The survey covered approximately a total area of about 113,000 m 2 . With the exception of one traverse line which had the length of 60 m, each of the remaining traverse lines had a length of 120m. The results from the data analysis indicated that, the surveyed area is underlain by three geological units although results from two traverse lines revealed two geological units. The P-wave velocity of the first layer ranges between 335.00 -468.00 m/s and the average velocity of 391.57 m/s. It has a thickness range of 5.0 -27.5 m with an average thickness of 16.25 m. The layer is interpreted as a weathered layer and consist of soil and dry loose sand which might be formed as beach deposit. The second layer has P-wave velocity range of 590.00 -1133.00 m/s and the average velocity of 881.71 m/s. The layer thickness ranges between 14.5 -31.0 m and the average of 25.80 m. The layer may consist of unconsolidated water-saturated sand and clay. The last layer detected by this survey has P-wave velocity range of 1068.00 -2724.00 m/s and the average of 2074.20 m/s. The layer is interpreted as the bedrock underlining the surveyed area. The layer may consist of gravel, sandstone and limestone.
The electromagnetic profiling and Vertical Electrical Sounding (VES) data were acquired from some communities in the Twifo -Hemang Lower Denkyira District of the Central region of Ghana, in order to determine zones of high groundwater potentials and to recommend suitable sites to drill boreholes for community water supply. The research reported here covered three communities namely; Esukese Ekyire, Kwanyarko. First the electromagnetic measurements were carried out, qualitative interpretations of the data were carried out and weathered rock zones were identified. Then the VES measurements using Schlumberger array were conducted at points on the electromagnetic traverse that displayed weathered zones. ZONDIP1D software was used in creating 1D sounding curve models of geological subsurface structures beneath the sounding points. Results of the modelling suggest that the communities are underlain by three to four geological layers. Interpretations of the 1D inversion of the VES data provide the resistivities and thicknesses of subsurface layers. On the basis of resistivity values and thicknesses of the layers in the 1D models, sites were recommended to drill boreholes for community water supply.Keywords: groundwater exploration, EM profiling, vertical electrical sounding, Ghana, weathered zone Gana'da bazı topluluklarında elektromanyetik ve elektrik rezistivite yöntemlerle kullunılarak yeraltı su kaynakları araştırması ÖZ Gana' nın merkez bölgesinde bulunan Twifo -Hemang Lower Denkyira ilçesindeki bazı topluluklardan yüksek yeraltı su potansiyeline sahip bölgeleri belirlemek ve belirlenen bu yerler doğrultusunda toplulukların su ihtiyacını karşılayabilecek uygun sondaj yerleri önermek için Elektromanyetik (EM) Profili ve Düşey Elektrik Sondajı (DES) verileri alınmıştır. Bu çalışmada, sırasıyla Esukese Ekyire, Kwanyarko ve Nyameyeadom kasabalarına ait etüd sonuçları tartışılacaktır. İlk olarak, EM ölçülerin alımı gerçekleştirilmiştir. Daha sonra EM verileri nitelik olarak yorumlanmış ve bunun sonucunda çatlak ve/veya kırık zonları tespit edilmiştir. Schlumberger elektrot dizilimi kullanılarak DES ölçümleri kayaç bozunması gözlenen noktalarda elektromanyetik ölçüm alınan yerlerde yapılmıştır. ZONDIP1D yazılımı, sondaj noktaları altındaki jeolojik yeraltı yapılarının 1D sondaj eğri modellerinin üretilmesinde kullanılmıştır. Modellemenin sonuçları bölgede üç veya dört jeolojik zon bulunduğunu göstermiştir. DES verilerinin 1D ters çözümü yorumlamaları katmanlarının özdirenç ve kalınlık değerlerini vermektedir. Su temini için gerekli olan sondaj kuyu yerleri 1D sondaj eğrisi modeli ve yeraltı katmanlarının kalınlıklarına göre önerilmiştir.
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