The study area lies between 8.92N-9.20N and 7.25E-7.60E in Abuja Federal Capital Territory (FCT) as in Figure 1. It is bounded in the east by Nasarawa State, north by Kaduna State, west by Niger State and south by Kogi State.

The topography of Abuja is undulating with hills and inselbergs that rise northwestwards to a maximum of 1060 m above sea level. There are extensive plains found between hills in the study area. The Zuma rock stands out clearly on its own as the most conspicuous Inselberg at the boundary of the Abuja with Niger State. The lowest elevations are in the southwestern flood plains of the River Gurara, about 76 m above sea level. The rivers rise from the hills in the northeast and flow to the southwest. The area is drained by many rivers in and around Abuja including Rivers Gwagwalada and Usmanu while Rivers Wupa, Wosika and other smaller seasonal southerly-flowing streams form the tributaries and drain the study area. The drainage pattern generally varies from trellis to dendritic. The major rivers join at Nyimbo village to form a tributary of River Niger in the south. These rivers depend on rainfall for their recharge. As such, their stages are high in rainy season and decrease drastically during the dry season.

The area has its highest temperature of about 36˚C during the dry season, November to March. During the rainy season April to October, the temperature drops to a maximum of 24˚C [9] . The annual rainfall ranges from 1100 mm to 1600 mm [10] . Two types of vegetation occur; the forest predominantly of woody plants thorn bushes and trees in which grasses are virtually absent comprise mainly of secondary forest, which is continuously degraded for subsistence farming and habitation and the savanna herbs and shrubs, the study area being in Guinean Savanna Vegetation Zone of Nigeria.

The geology of the study area has been described by many workers, including [3] [9] [11] . The study area is underlain by Precambrian rocks of the Nigerian Basement Complex which cover about 85% of the land surface and cretaceous sedimentary rocks belonging to the Bida Basin which cover the remaining 15% as in Figure 2.

The aquiferous formations in Abuja FCT are mostly Granite-Gneiss fractured rock and their regolith.

In Granite-Gneiss-type rocks, single weathering and erosional processes induce similar geological structures. From field observations, borehole lithostratigraphic sections and by comparing various case studies in similar terrain, a modified hydro-geological conceptual model of migmatite/gneiss-type fractured rock aquifers in Africa postulated by [1] has been adopted in Abuja FCT.

In this model, precipitation infiltrates through the sandy regolith and groundwater flows through:

1) Weathered basement regolith

2) Fractured/fissured basement

3) Deep large regional fractures with a larger fraction flow volumes.

Groundwater is stored in:

1) The weathered basement or regolith in the inter-particulate pore spaces and relics of fractures. Though here storage is directly impacted by seasonal variations of precipitation

2) The fracture/fissure insular network infrastructure of unconnected joints, fissures and fractures

3) The fracture/fissure interconnected network infrastructure which also serves as the major conduit/channel for storage and flow of groundwater.

The weathered regolith, the local fractures and the regional fracture network form a single continuous hydraulic unit making a single weathered basement fractured-rock aquifer.

Abuja has an undulating relief of hills and valleys. The land surface is covered by top soil in most areas as in Figure 3. The topography of the Abuja is varied with the lowest elevations in the extreme southwest at the floodplains of the River Gurara, about 76 m above sea level and it rises irregularly northwestwards to a height of 760 m above sea level. There are numerous hills that occur in the area but the Zuma rock stands out clearly on its own as the most conspicuous Inselberg at the boundary of the Abuja with Niger State.

Groundwater levels range from 3 - 12.5 m. High water levels are at Kwalita, Galadimawa, Wupa, Pigba, Kurundu and Pyeti whereas low values are at Pedegma, Nukuchi, Durumi and Zango as seen Figure 4. The shallow depth to water levels which in some areas could increase surface runoff into boreholes and thus increase the number of microorganisms in the water. These low depths to water could also be prone to pollution if the wells are not appropriately constructed and protected.

The temperatures of groundwater in Abuja range from 26.0˚C - 36.1˚C as shown in Table 3. These groundwater temperatures are close to air temperatures indicative of phreatic aquifers. Some bacteria can be killed at elevated temperatures > 15˚C or higher, thus the temperatures within the study area are suitable for the survival of microorganisms. High temperatures are at Koro, Kade, Galadima, Mabuchi, Kushingoro and Karunounmaji whereas low temperatures are at Kgjini, Jiwa, Dadayi, and Sabuyi as in Figure 5.

The pH of groundwater samples in the study area ranged from; 4.8 - 7.9 as shown in Table 3. The value of pH of a water sample is recognized as an index of classifying groundwater as acidic < 5.5, slightly acidic 5.5 - 6.5, neutral 6.5 - 7.5, slightly alkaline 7.5 - 8, moderately alkaline 8 - 9 and alkaline > 9. From the above results, it is indicative that water in the study area is acidic to alkaline. High pH values are at Kwalita, Kukwaba, Kufaniajiji whereas low pH values are at Danama, Bazango, Chikakoro, Dutse, Kade, and Galadima as seen in Figure 6.

The observed conductance in the study area ranged from 13.4 - 1634 µS/cm as shown in Table 3. The measurement of conductivity gives a good indicator of the concentration of dissolved salts in water. In the present study EC values were in the permissible limits as in Figure 7.

The values range from 17.42 - 1094.78 mg/L with the highest value observed at Kuru, Gwagwa, Kurundu, and Barwa whereas low values are at Nyana, Dam Dam, Jikoko, Galadima, Kade, Mabuchi, and Jikoko as seen Figure 8. TDS represents the amount of inorganic substances. High TDS is commonly offensive to taste. A higher concentration of TDS usually serves as no health threat to humans until the values exceed 10,000 mg/L.

Several biological and inorganic processes taking place in the subsurface may consume dissolved oxygen and deplete the DO levels. The water samples collected in the study area had DO between 0 and 10 mg/L and a spatial variation as in Figure 9. Low DO levels can be attributed to heterotrophic biological respiration.

Total bacterial count is used to estimate the total amount of bacteria in groundwater and indicates the overall microbial status of the water [8] . Total bacterial count ranges from 0 - 5120 as in Figure 10. These values are far above the maximum permissible limits of NIS and WHO.

Faecal coliform are a bacteria species belonging to the total coliform group. This bacterium is found in the faces of warm-blooded animals, but, unlike total coliforms, they are not present naturally in the environment [23] . Faecal coliforms range from 0 - 170 as in Figure 12. This result indicates that the water is grossly polluted by potentially harmful microorganisms. These pathogens may be of faecal origin and water that contains them is not suitable for drinking and/or cleaning purposes and could cause epidemics of water borne diseases to the population.

Coliform bacteria are a group of enteric bacteria that includes E. coli and Enterobacteria species. They are Gram negative, facultative anaerobic, non-sporing rods that may be motile or not. They are generally not harmful themselves; they indicate the possible presence of pathogenic bacteria, viruses and protozoans [24] . Coliform bacteria range from 0 - 438 as seen in Figure 13. The presence of

coliform bacteria in drinking water increases the risk of contracting a water-borne illness. The presence of these coliform bacteria could be as a result of the following; a missing or defective well cap, contaminant seepage through the well casing, contaminant seeping along the outside of the well casing and well flooding. According to Cheesbrough classification, 23.4% of the samples are acceptable for drinking whereas 76.6% are unacceptable for drinking indicating that the water is polluted by potentially harmful microorganisms as shown in Table 5. These pathogens may be of faecal origin and water that contains them is not suitable for drinking and/or cleaning purposes.

Salmonella species are non-spore-forming, predominantly motile Enterobacteria with cell diameters between about 0.7 and 1.5 µm. Salmonella species values range from 0 - 223 as seen in Figure 14. The isolation of Salmonella species from groundwater samples means that the direct consumption of such water without treatment may be very risky. From this study, the fractured rock aquiferous formations could be contaminated through joint, fissures and fractures by run-off.

Salmonella species causes typhoid fever which can be spread through contaminated water.

Total bacterial density range from 0 - 86.5 as seen in Figure 15 and shown in Table 6. Most bacteria are able to tolerate slight temperature and pH changes [25] . Significant microbial activity in groundwater is found at temperatures of 15˚C or higher [26] .

The general belief is that groundwater percolating and infiltrating through aquiferous particulate matrix is relieved of its physical, chemical and biological impurities; is pure and fit for human consumption. And that, deeper boreholes are supposed to contain little or no microorganisms usually removed by extensive filtration as water percolates through the soil [27] . Probably this holds true for some deep multilayered aquifers where the geology does not make it chemically unsafe and is deep enough for most bacteria to live in or sealed top-bottom. For the rest of aquifers, this is nothing but a myth. In most African Granite-Gneiss fractured rock aquiferous (FRA) formations; the regolith is thick in the valleys, thin at the slopes and absent (Bare unweathered or eroded rock surfaces) at the hilltops. As such, the joint, fissure and fracture network that constitute the voids of aquifers are semi-open to open channels since in most cases the weathered regolith retains the fracture features. Coupled with the abundance of mammals (Cattle, sheep, goats, dogs and other wild animals that abound) their droppings will only help in increasing the potential for non-point pollution. The construction of toilets and latrines in these terrains is difficult and in most parts expensive for poor denizens. Faced with this challenge they squat in the bushes or excrete in poorly constructed latrines which then act as point pollution sources of biological contaminant to these aquifers: This is the reality.

This explains the results of the groundwater biological quality in Abuja FCT, those of [28] in Kaduna [29] in Jigawa and [30] in Ethiopia who have all found groundwater in Fractured rock aquifers to be unfit for human consumption by [16] [17] [18] .