Columnists Features

Monitoring sinking of boreholes a need

JULIUS LUNGU
DRIVING from the Kabwe roundabout in Lusaka to the airport turnoff (and beyond) on Great East Road, one is greeted, all the way, by a number of water borehole drilling and exploration companies whose names are conspicuously painted on walls in huge fonts.
One wonders first of all whether it is one company or several competing companies vying for few customers that require their services. The question is: is Lusaka Water and Sewerage Company (LWSC) not providing the right amount of water in terms of availability, quality, cost and pressure?
According to National Water and Sanitation Council (Nwasco), the Water Supply and Sanitation Act No. 28 of 1997 requires water supply and sanitation (WSS) providers to ensure efficient, affordable and sustainable services within their service areas. This implies that the service providers must guarantee their customers a certain and defined level of service for a specified price ensuring, therefore, “value for money”. Service level guarantees (SLG’s) are, therefore, a must and should be a basis for holding the service providers to account.
This being the case, and if monitored, is there any need for one to sink a borehole? The answers may be mixed and varied depending on several factors. What we need is a regulatory framework for monitoring the sinking of boreholes.
The Water Resources Management Act No. 21 of 2011 saw the establishment of the Water Resources Management Authority (WARMA) whose mandate is to provide for the management, development, conservation, protection and preservation of water resources and their ecosystems.
WARMA is currently developing regulations and guidelines governing the sinking of boreholes. This will include abstraction permits, licensing, fees and so on. Hopefully this could be finalised by the end of this year. This should hopefully also guard against dry boreholes which consumers are sometimes asked to pay for with no recourse. This indeed is long overdue but nonetheless welcome.
Much as we would all wish to have a borehole at our premises, this comes at a price. Apart from the cost of sinking the borehole, add all associated costs of pump, casings, tank stand and reservoir and throw in the electricity bills for pump operation. Boreholes can have an adverse effect on foundations, due to drawdown on water-table level and variation of soil moisture content levels and this happens mostly when the borehole is not sunk in a stable aquifer (water-bearing rock).
One might ask: how deep should a borehole be? Well, there is no set answer for how deep a borehole needs to be. Put simply, the borehole should be as deep as is required to reach the aquifer. The average depth of a borehole is between 60 metres and 80 metres but this can be less as well as significantly more. The depth of a borehole very much depends on where you are and the underlying geology.
Minimum distance between the borehole and existing structures must be observed.  During pumping, a borehole pump produces a ‘cone of depression’ or drawdown. This is the influence zone of where water is being abstracted. Where possible, any new borehole should be outside this zone to ensure that one borehole does not affect another and existing foundations must be outside this zone.
The same applies for minimum distances away from any potential source of contamination such as septic tanks and pit latrines. A qualified hydro-geologist should be able to offer advice including geophysical surveys. I would further suggest that an environmental project brief must be carried out and approved by the Zambia Environmental Management Agency before one embarks on sinking a borehole.
The author is technical director at JKL Associates. jklungu@engineer.com

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