Before the ground is broken and your borehole is drilled, there are a couple of preliminary steps that must be done.
One of which is a hydrogeological survey.
What is a hydro-geological survey?
A hydro-geological survey, also known as a water or hydrological survey, is an assessment of certain parameters that evaluates the possibility and quality of groundwater on a potential drill site.
Ideally, a geologist hired by the client conducts the survey. If a client has trouble finding one, the company recommends at least two from which the client may select. This is done to maintain the credibility of the survey and avoid any liability that may arise.
How is a hydro-geological survey done?
A geologist uses a combination of geophysical methods in the assessment of geological subsurface conditions. These methods include:
- Resistivity
- Vertical Electrical Sounding (VES)
- Horizontal Electrical Profiling (HEP)
- Very Low Frequency (VLF)
- Fieldwork
What is the purpose of a hydro-geological survey?
The survey aims to:
- Identify the availability of aquifers
- Describe the structure, lithology, and general geology.
- Based on groundwater flow direction, routes, and rates of flow, estimate the expected yield.
- Evaluate the quality of groundwater
- Evaluate catchment risk (the potential for planned and existing activities that could result in groundwater contamination)
- Health and environment risk assessment
- Determine an ideal drill site based on the information above.
What does a hydro-geological survey report contain?
The report’s cover page contains contact details for the client and geologist. This includes the client’s and geologist’s name, address, and plot location. The survey report’s preparation date is also included.
The report lists the origins of the local water sources,’ its input, flow, and outflow. This information is important in the selection of a drill site.
The climate and minimum rainfall of the area of the proposed area are included. This information is critical in evaluating the potential capacity of the proposed borehole and whether it’ll meet the client’s needs.
The topography and geology of the site are also noted in the report. This section focuses on the type and rock formation on a proposed site. This will help the borehole contractors to anticipate the complexity of the project.
The geologist will also note the quality and placement of aquifers (underground layer of water-bearing, permeable rock, rock fractures, or unconsolidated materials (gravel, sand, or silt). It is the placement of these aquifers that will inform how deep the borehole will go.
How long does a hydro-geological survey take?
A hydro-geological survey takes up to a week to complete.
How much does a hydro-geological survey cost in Kenya?
A hydro-geological survey is estimated to cost between Ksh. 50,000 and 60,000. These expenses can be higher for larger parcels of land.
