Hydrogeological Properties of the Rocks in Adansi Mining Area, Ghana

Groundwater is an important resource in the Adansi mining area as some communities in the area are not connected to the Ghana national water network. These communities therefore utilise groundwater for potable water supply. The hydrogeological properties of an aquifer coupled with climatic conditions and geomorphology determines how much groundwater exists in that location. A hydrogeological study of the rocks in the Adansi area was carried out to obtain the aquifer hydraulic properties. Drilling and pumping test analysis information were used to assess these properties. The average borehole depth in the area was 44.3 m whilst the average static water level is 10.75 m. There is a general decrease in yield with an increase in borehole total depth. There is also no strong correlation between aquifer saturated thickness, yield and drawdown. Transmissivity of the aquifer decreases from the phyllite, argillitc sediments, granites to sandstone. Three hydrogeological regimes (> 0.9 m/day, 0.9 – 0.09 m/day and < 0.09 m/day) were also realised based on the hydraulic conductivity. The spatial distribution of the hydraulic properties suggests the influence of geological structures on the occurrence of groundwater in the area. Keywords: Hydrogeological Properties, Mining, Hydraulic, Drilling, Groundwate

Rainstorm Intensity–Duration–Frequency Model for Tarkwa, Ghana

Rainstorm intensity–duration–frequency relationship is a tool required for appropriate planning and designing of drainage systems. In this study, 22 years of annual peak daily rainstorm data distribution was tested to verify if it followed Lognormal, Gumbel, or Log Pearson Type III distribution. The distribution to which it belonged was used to build rainstorm intensity model of 0.5, 2, 5, 8, 10, 12, 15, 18, and 24 h durations. The findings revealed that the observed peak annual rainstorm followed Gumbel and Log Pearson Type III distributions at 0.05 significant level. Sherman rainstorm intensity model was also adopted and the parameters determined. Data generated with the Gumbel distribution function best fitted the Sherman model followed by those by log Pearson Type III. The rainstorm models developed with Sherman’s equation were recommended for use in the Tarkwa area. Keywords: Flood, Gumbel Distribution, Water Resources, Rainstor

Groundwater Vulnerability Assessment using Drastic Index and GIS in Kumasi Metropolitan Assembly, Ghana

The assessment of groundwater vulnerability to contamination has become an important element for landuse planning and groundwater resource management. This study aims at estimating groundwater vulnerability using an integration of Geographic Information System (GIS) and DRASTIC method in the Kumasi Metropolitan Assembly (KMA). The groundwater vulnerability map was prepared using index and overlay analysis with the aid of Arc GIS 10. The DRASTIC Index (DI) computed ranged between 70 and 164 as the lowest and highest contamination potential respectively. The eastern and western flanks and north-west tip of KMA are underlain by the granites which bear water due to the combined effect of weathering and fracturing and are dominated by "Very High", "High" and "Moderate" vulnerability based on the vulnerability index computed. The "Low" and "Very Low" vulnerability are located at the northern, central and southern parts of KMA which are underlain by phyllites. These suggest that boreholes located in the Birimian metasedimentary units which comprise mainly phyllites would be less likely to be vulnerable to contamination than those located in the intrusive rocks dominated by the granites. Keywords: Groundwater Vulnerability, Soil Media, Hydraulic Conductivity, Overlay Analysi