Artesian Wells in The FCT.

By: Prince Kiddo Mekwunye

Artesian boreholes are wells drilled into confined aquifer whose hydraulic head from the zone of recharge is higher than the point drilled. This can be best explained by Darcy’s law of fluid flow in a media. In this condition, the borehole water flows continuously from the casing without the aid of a pumping machine. The volume, flow rate and height are factors of the elevation difference of the recharge zone of the aquifer and the aquifer material.

Several artesian wells have been recorded in the sedimentary basins in Nigeria which have been studied. All recorded artesian wells were linked to the stratigraphic setting of the sedimentary basin. Example is the Ajali sandstone confined by Nsuka Formation and Imo Shale. Artesian boreholes drilled into this geologic formation can be seen at Oji River area of Enugu state.

Occurrence of artesian wells in basement complex have not been properly reported or studied due to scanty research on groundwater characteristics of basement complexes. Groundwater occurs as water table aquifer in the overburden and confined aquifer in fractures embedded in the rock mass. Over the years, groundwater exploitation in basement complex in Nigeria has been the earlier stated aquifer (water table aquifer). This is due to the use of crude drilling equipments and none application of high resolution geophysical equipments for hydro geophysical survey to detect fractures, fixtures and fault lines inside the rock mass which can be saturated with fluid.

Recent deployment of advanced technologies in groundwater exploration and exploitation in basement complexes have enabled the detection of deep aquifer in fractures, fixtures and fault lines in the basement complex.

Judging by the characteristics of an artesian well, most confined aquifers in basement tend to exhibit the artesian characteristics but often times due to the head difference from the recharge zone to the borehole point, the water table virtually rises to a point but not to a surface flow. In some areas within flood plains, boreholes exhibit seasonal artesian condition during the rainy season. These areas are presumed to be controlled by local aquifer recharge factors.

Within the past 4years, about 5 distinct artesian boreholes have been encountered in Abuja and its environs whose flow had preceded years. Below are their references;

Although these artesian boreholes have not been properly studied to determine their flow rate, head flow and origin, some are presumed to be recharged by regional aquifer as their flow rate had been steady and continuous over the years.

Artesian wells of regional origin could be a factor for the depletion of groundwater at the recharge zones even when there are no many boreholes in the area. This needs to be studied. Proper GIS mapping of the artesian wells and tracing of their fracture source and orientation will help in understand possible inter-basin interaction of groundwater in these environs.

Proper studies of artesian boreholes in FCT and its environs will help in delineating highly prolific fractures thus design central municipal water supply system tapping the resource from these aquifers. Much gains as reduction of energy cost of pumping cannot be over emphasized as benefits of exploiting water from artesian boreholes. Groundwater usage and monitoring will be easier as this will reduce indiscriminate and multiple boreholes by individuals. This will also help in preserving groundwater quality as government can through her agencies protect the environment by regulating human activities within the recharge zones.

Groundwater dating using Isotope hydrology will help in understanding the source and age of water in these aquifers thus data can be used for effective and efficient planning of groundwater usage and management.

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