A multi-criteria decision analysis for groundwater potential evaluation in parts of Ibadan, southwestern Nigeria

Multi-criteria decision analysis based on Saaty’s analytical hierarchy processing technique has been used to establish groundwater potential distribution pattern across some highly populated parts of Ibadan metropolis in southwestern Nigeria. The technique weighted and ranked seven sets of thematic hydrological parameters derived from Landsat 8 OLI satellite imagery, 143 vertical electrical sounding (VES) geophysical data, and geological and topographical data. Filtered and enhanced Landsat 8 OLI satellite imagery, quality-checked and inverted VES data, and categorized geological and other ancillary data were analyzed and used to generate lineaments, subsurface geoelectric parameters and other terrain information employed to extract thematic hydrogeological parameters used to characterize the subsurface in terms of groundwater potential. Weighted, normalized and ranked derived thematic hydrogeological parameters (lineament density, drainage density, coefficient of anisotropy, aquifer thickness, overburden thickness, aquifer resistivity and lithology) were employed to generate groundwater resource potential map. The map delineates the study area into very low (6.5%), low (41.0%), medium (38.1%), high and very high (14.4%) groundwater resource potential zones. Regions underlain by quartzite/quartz schist rocks present medium-to-high groundwater resource potential, while regions underlain by migmatite and granite gneiss rocks mostly have very low–low groundwater resource potential. This study indicates that variation in groundwater resource potential across Ibadan situated within the basement complex terrain is mostly influenced by the heterogeneity of subsurface geology which varies rapidly in terms of rock distribution and associated hydrogeological indices.

HYDROGEOPHYSICAL INVESTIGATION FOR GROUNDWATER RESOURCE POTENTIAL IN MASAGAMU, MAGAMA AREA, FRACTURED BASEMENT COMPLEX, NORTH-CENTRAL NIGERIA

Vertical Electrical Sounding (VES) was conducted in Salbi farm in the fractured Basement Complex, North- Central Nigeria to determine the groundwater resource potential to serve for agricultural purposes. Four VES stations using Schlumberger electrode configuration with a maximum current electrode spread of 300m were employed for data acquisition. ZHODY software was employed in computing resistivities, depths and thicknesses of the various layers and curve types. Results indicate that the area is characterized by 3 distinct geoelectric layers inferred differently at the VES locations. One potential groundwater aquifer zone was delineated at VES 1, 2, and 4 within the fractured/weathered basement columns having depths ranging between 48.8 – 59.60m and resistivities ranging between 213 – 513 Ωm. These results suggest that boreholes for sustainable groundwater supply in Salbi farm should be sited either at VES 1, 2 or 4 location and screened at a depth ≥60.0m. Wells to develop this resource should be drilled to an effective depth of 40 to 60 m for optimum yields. It is recommended that pumping test be done in order to further determine the aquifer efficiency and productivity in the area. However, the aquifers at these locations have potentials for groundwater but may be vulnerable to contamination.

Evaluating the groundwater resource potential of the Dundas buried bedrock valley, southwestern Ontario: an integrated geological and hydrogeological case study

Population growth in the groundwater-dependent municipalities of southwestern Ontario has prompted interest in the exploration for new, previously untapped, groundwater resources. In this study, the groundwater resource potential of the sediments infilling a deeply buried bedrock valley network centred beneath the Region of Waterloo and the counties of Brant and Hamilton–Wentworth are explored. The objectives of this study are to further refine valley location and geometry, understand infilling sediments and their hydrogeological properties, and characterize waters contained within the aquifers to inform future water management decisions. Results of a regional ground gravity survey were instrumental in locating buried bedrock valleys and guided follow-up drilling. Continuous sediment coring and monitoring well installations were completed to target thick and coarse-grained sediment packages that, based on existing borehole data, showed aquifer potential. Hydraulic testing and groundwater sampling results provided valuable insights into groundwater quantity and quality. Highly transmissive aquifers, some worth investigating further, have been identified within portions of the valley network. The aquifers appear to occur at a number of stratigraphic positions and do not necessarily occur as the deepest unit overlying bedrock. Bedrock topography likely played a role, however, in their preferential preservation. They are commonly overlain by thick sequences of relatively impermeable sediments, providing excellent protection from anthropogenic contamination. Information from water chemistry, however, does suggest hydraulic connection to the surface at some locations. Groundwater quality and quantity information combined with a conceptual three-dimensional geologic model aids in the selection of groundwater resource exploration targets within the untapped resources of the deep, Dundas buried valley sediments.

Groundwater potential of the eastern Kalahari region of South Africa

An integrated approach involving geological, borehole data, hydrogeochemical and environmental isotope analyses was used to determine the groundwater potential of the eastern Kalahari region of South Africa, an area to the west of Mahikeng that stretches northward from the Orange River into Botswana. The total groundwater resource potential for the eastern Kalahari region of South Africa is estimated at 10127 Mm3/a, with the Kalahari Group aquifer showing the greatest potential, comprising 51% of the total resource. The storage capacity of the Kalahari Group aquifer (7130 Mm3) is also impressive, estimated to be more than twice that of the dolomite aquifer (2728 Mm3). Despite having such great potential, the aquifer is not actively recharged and is often associated with very saline water that is not suitable for human and livestock consumption. The limestone and dolomite aquifers of the Campbell Rand Subgroup, as well as the weathered granitic rocks of the Archaean basement, are considered as the most prospective water bearing formations, with a groundwater resource potential estimate of 1981 Mm3/a and 1845 Mm3/a, respectively. Aquifers with the least potential in the project area comprise the fractured basement rocks of the Kraaipan - Amalia greenstone belt, with a groundwater resource potential of 26 Mm3/a, and the fractured sedimentary rocks of the Asbestos Hills Subgroup, with a groundwater resource potential of 108 Mm3/a. The calculated groundwater storage and resource potential in the eastern Kalahari region of South Africa satisfies a large proportion of the water demand in the region.