Peer Review Article.
Author: Prince Kidochukwu Mekwunye.
Groundwater houses over 30% of fresh water on planet earth. This makes its role in the Water cycle very conspicuous.
In recent years, the emergence of technologies to harness groundwater and human perceptions of groundwater quality have resulted in massive drilling of water boreholes of variable depth and capacity to meet human needs. However, while this is mainly to ameliorate the lack of potable water, there is less awareness in the public domain on the effect of such human activities as unregulated drilling of boreholes.
What is a borehole? A borehole is a hole dug with the aid of a machine or manual auger to intercept an aquifer. Its diameter and depth is subject to the aquifer parameters, the quantity and quality of the water. Its quality varies from one purpose or the other ranging from human and animal consumption to industrial, agricultural purposes and other such purposes.
Drilling of boreholes in different geological formations require different technical approaches. These approaches are designed models to manage drilling activities to sooth the underlying aquifer bearing rock, manage soil structure, reduce environmental impact and manage groundwater contamination.
While mud drilling is recommended for unconsolidated geologic formations, DTH is recommended for consolidated and crystalline geologic formations. None can substitute the other as any such result will be abortive.
The advent of heavy duty DTH drilling Rigs and the quest for quick drilling and fast returns on investment have caused most drillers to adopt this technology for drilling in unconsolidated rigolith layers of basement complex even when it’s too thick in depth and highly aquiferous. In most cases, the effect on soil structure is immediate, leading to distortion of buildings, roads and even minor tremors due to differential settlement of disturbed soil structures. Caving in of saturated silty layers result to artificial sinkholes which leads to collapse of borehole of adjourning engineering structures.
Siting of boreholes also requires professional advice as environmental geoscientists have proven massive interactions of groundwater with the environment especially municipal dump sites, agricultural waste, industrial effluents, oil spills and even domestic waste.
In Nigeria today, little or no attention is accorded to the issues bordering on regulation of drilling activities in towns, cities and villages. Borehole drilling companies, both local and foreign owned, spring up daily, managed by pure businessmen whose motive is profit and no consideration of the environmental impact of their activities or efforts to conserve this threatened resource.
On the average, within the past seven years, over 100,000 boreholes of different depths and capacity have been drilled within the FCT and its environs. These are 100,000 new discharge points for the basement aquifer which in most cases have limited recharge. This has led to high depletion of shallow aquifers especially those within the overburden/weathered layer of basement complex.
This noticeable effect has within six years increased the average borehole depth in Abuja from 40m – 80m within the period under review. 90% of these boreholes were drilled without proper reconnaissance surveys of the environment vis a viz an impact assessment. They are drilled with uncalibrated equipment, unapproved methods and no submission of borehole report for record purposes, research and development.
Boreholes are drilled next to dump sites, septic tanks, animal pens, storm water canals and even sewage lines. This affects greatly the quality of groundwater. In recent times, water samples collected from boreholes of over 60m depth in Idu, Dobi, Maraba and Suleja have shown presence of fecal colliform. This is alarming and calls for urgent attention as it indicates massive interaction of our groundwater and human/animal waste.
I therefore appeal to the government agencies saddled with regulations of borehole drilling activities to as a matter of urgency roll out modalities to check the activities of drillers and drilling companies. Government in all segments should invest more in pipe borne water supply as this will provide trusted potable water and help reduce reliance on boreholes.
The public is advised to seek for professional advice and services in borehole construction as the negative effect of using quacks due to ignorance is not an excuse.
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