Glossary

Apron – a concrete floor surrounding a drilled water well to provide a relatively clean environment and control the drainage of spilled water away from well.

Borehole - a water well or hole which is drilled in the ground and partially or fully lined for the abstraction of groundwater.

Borehole design - choosing the depth, diameter and lining materials of the borehole and the drilling technique to be used.

Borehole development - the act of cleaning a borehole after construction by flushing or other means until the water from the hole is clean and free of fine materials.

Borehole siting - the selection of the optimal location of the boreholes by the community as well as with either hydrogeological and/or geophysical means to ensure the design yield.

Biofouling - Bacteria in the aquifer mediate the deposition of iron and other metals, resulting in the formation of a biofilm on the well screen and casing. When the accumulation of this biofilm causes problems of incrustation or corrosion of the well screen and casing of the water well, the process is known as biofouling.

Community selection process - the process by which communities are selected to benefit from a borehole.

Community sensitisation generally refers to the process whereby water users in a community are informed of the technical options for a water source improvement and the requirements that they have to fulfil in order to benefit from one.

Community mobilisation – is the process of preparing a community for the arrival of the contractor (or NGO) who will construct the improved water supply (e.g. a drilled water well) and arranging for the subsequent management and maintain of the source. Community mobilisation may also include the collection of a cash or in-kind contribution towards construction by the local government, NGO or donor involved.

Data - all facts about a borehole collected before and during, drilling, borehole development, completion and pumping test. 

Derogation is the effect of pumping a well on the seasonal flow from springs, the drawdown in nearby wells, or the drying of wetlands.

Drawdown refers to water level lowering caused by groundwater pumping.

Drilling contractor is a private company or NGO engaged in the drilling of boreholes for water supply boreholes.

Drilling technology - the method of construction and equipment used in making the drilled water well.

Engineers Estimate – a reflection of a fair and reasonable price for the construction work, as determined by a professional (including labour, equipment, materials and a reasonable value for overheads and profit).

Gravel pack – an artificially placed permeable annular backfill, which is placed around the screen of drilled water well. It needs to be at least 70cm thick to be effective. If it is thinner then it is actually a formation stabiliser (see below).

Formation stabiliser - if a well can be developed naturally, or the annular space around the screen is limited, or both a permeable backfill, known as a formation stabiliser, is placed simply to fill the annular space and prevent the formation from collapsing onto the screen.

Hydrogeological consultant – the professional company or individual responsible for water well siting and design.

Interference - the effect that pumping from a well has on the drawdown in neighbouring wells

Lease to purchase agreement – a rental agreement with an exclusive option of the right of first refusal to later purchase the item.

Method statement - a document that clearly sets out the details of how the work will be carried out.

Monitoring - the periodic checking of the functionality of boreholes, pumps and aprons and community management of the water source as well as water levels and water quality.

Operation and maintenance - running and repairing the water well, pump and apron so that sufficient clean water can be pumped at all times throughout its designed life and the general area of the well is kept clean. It also encompasses wellhead protection, post-construction support and access to spare parts for the pump and well maintenance.

Planning at community level – a pre-project assessment of the existing water and socioeconomic situation of the community to determine the most suitable water facility.

Procurement - the process of selecting a drilling contractor, hydrogeological consultant or supplier to undertake a particular service or construction.

Quality control - ensuring that both the pumps and spare parts supplied and well construction adhere to the specifications.

Yield – this is a term which is very often misused. Drilling contractors often refer to yield when they actually mean (a) the flow measured during air-flush drilling or (b) the rate at which the water was pumped during the pumping test. In reality the deliverable well yield depends on the aquifer geometry and hydraulic properties, combined with the maximum permissible drawdown in that particular situation. It should be noted that this definition takes no account of renewable groundwater resources.