Hydrological Survey: The Exact Locaton, Depth and Quality of Water
A hydrological survey is a crucial step that ensures the success of drilling a borehole. Think of it as a sneak peak of the geology of the target location, which is an important part of determining the availability of water resources before spend ing your hard earned money.
This process helps in determining the optimal drilling location, depth, and the expected quality of water. It also assists in preserving the environment and avoiding any negative impacts on nearby water resources.
A proper hydrological survey can also save time and money, as it minimizes the risk of drilling in an inadequate location.
In addition to location selection, hydrological surveys provide valuable information for borehole construction and completion.
This process includes casing and sealing the boreholes, ensuring proper hydraulic connection between the well and the aquifer, and evaluating the performance and efficiency of the borehole system.
Ultimately, the results of these surveys contribute to the responsible and sustainable management of groundwater resources for various applications, such as drinking water supply, irrigation, and industrial use.
Key Takeaways:
- Hydrological surveys help select suitable locations for drilling and assess groundwater resources quality and quantity.
- Survey data informs borehole construction and completion, ensuring efficient well and aquifer connections.
- The information gathered allows for responsible management and sustainable use of groundwater resources.
What Details are Included in a Hydrogeological Survey Report?
A hydrogeological survey report contains essential information collected during the investigation process. The report usually includes:
- Geological data: Information about the rock types, soil, and geological formations present at the site, which plays a vital role in determining the availability of groundwater.
- Water resources: Details of existing water resources, such as nearby rivers, lakes, and other sources that may influence the groundwater system.
- Water quality: Chemical analysis of water samples collected from wells to ensure the water is safe for consumption and other uses.
- Aquifer information: Characteristics of the aquifer, which is a geological formation that holds and transmits water.
- Recommendations: Suggestions on the optimal drilling location, depth, and the expected yield capacity of the borehole.
You can book your hydrological survey with Wotech Kenya today by calling 0720 528 274.
Cost Estimate of a Hydrogeological Survey in Kenya
The cost of a hydrogeological survey in Kenya may vary depending on factors such as the size and complexity of the project, the location, and the required resources. However, to give you a general idea, here’s a breakdown of the estimated costs:
- Preliminary assessment: This includes desk studies, geological mapping, and geophysical investigations. The cost ranges from 50,000 to 150,000 KES.
- Water quality analysis: The chemical analysis of water samples typically costs around 5,000 to 15,000 KES per sample.
- Drilling: The cost can range from 4,000 to 20,500 KES per meter, depending on the location and casing required.
Please note that these figures are only estimates and the actual costs may vary depending on specific project requirements.
Pre-Survey Preparation
Before embarking on a hydrological survey for a borehole, proper planning and preparation are essential for a successful and efficient project. In this section, we will discuss the steps involved in pre-survey preparation, including selecting the survey site and gathering preliminary data.
Selecting the Survey Site
The first step in conducting a hydrological survey for a borehole is to select an appropriate site. This decision should be made collaboratively by geologists and hydrologists. To select the best possible site, several factors should be considered, such as:
Accessibility: The site should be easily accessible for the survey team, equipment, and potentially drilling machinery in future phases.
Geology: Proper knowledge of the local geology is crucial, as this will influence the water-bearing capacity and quality of the borehole. Collaborating with experienced geologists can help understand the geology of the area.
Water demand: Consider the water requirements of the nearby communities, industries, or agricultural activities that might rely on the borehole for their water needs.
Regulations and permits: Ensure that all necessary permits have been obtained and follow any applicable regulations for borehole drilling and groundwater usage.
Gathering Preliminary Data
Once the survey site has been selected, gathering relevant preliminary data is crucial for an efficient hydrological survey. The following data sources can aid in the preparation process:
Existing local records: We consult available databases, reports, and records to gather information on previous hydrogeological investigations and projects in the surrounding area. This can give us an insight into the water quantity and quality in the region.
Topography: We assess the topographical characteristics of the site, which can influence the hydrogeological properties and provide important information for the survey.
Geophysical Surveys: We conduct a geophysical survey before initiating the hydrological study will help identify the type of geological formations, the depth of water-bearing zones, and potential drilling targets.
Water Quality: We obtain data on the water quality in nearby wells, as this will help determine the anticipated quality in the borehole. Also, we consider reviewing any known contamination sources and their potential impact on the groundwater quality.
Network of Groundwater Level Analyzer (SDM): We utilize available SDM data if the site is located within a monitored area. The SDM is a valuable instrument for groundwater management and provides essential information on water table elevation and trends, which can help to plan the survey better.
By carefully selecting the survey site and gathering all necessary preliminary data, the hydrological survey for a borehole can be carried out more effectively and efficiently, leading to a successful and sustainable groundwater resource project.
Survey Methods and Techniques
In this section, we will discuss various methods and techniques used for hydrological surveys in boreholes. These include Resistivity and Conductivity, Drilling and Sampling, and Hydraulic Testing.
Resistivity and Conductivity
Resistivity and conductivity are common measurements taken during borehole geophysical investigations. They provide information about the subsurface’s physical and chemical properties. The two methods work together, as resistivity measures how difficult it is for an electric current to pass through the material, while conductivity measures how easily the current can pass through.
Borehole resistivity logging is useful for determining lithology and identifying groundwater-saturated zones. Conductivity logging, on the other hand, helps detect the presence of dissolved ions in the groundwater, which can indicate water quality or potential contaminants. Together, these methods provide valuable data for hydrogeological studies and borehole investigations.
Drilling and Sampling
Drilling and sampling are essential techniques for collecting information from the ground during borehole surveys. Different drilling methods are used depending on the geological conditions and the objectives of the survey.
- Rotary drilling: In this method, a drill bit rotates at high speeds to cut through rock, producing drill cuttings that are analyzed for lithology, mineralogy, and other properties.
- Percussion drilling: This method employs a heavy drill bit that hammers into the ground, breaking the rock into fragments for collection and analysis.
Once the drilling has been completed, core samples are collected from the borehole for in-depth analysis. They provide valuable data on the subsurface’s rock types, fluid content, and structural features. Additionally, geophysical logging techniques can be employed to further investigate the borehole and its surroundings.
Hydraulic Testing
Hydraulic tests, such as pumping tests, are essential for assessing an aquifer’s potential yield and hydraulic properties, such as transmissivity and storativity. These parameters are critical in managing groundwater resources and designing water extraction systems.
A pumping test typically involves:
- Installing a pump in the borehole
- Pumping water at a constant rate for a predetermined time
- Monitoring the water levels and drawdown in the pumping well and nearby observation wells
- Analyzing the data to determine aquifer properties
One key parameter obtained from pumping tests is the specific yield. It represents the quantity of water released from the aquifer due to the drawdown caused by pumping. Understanding specific yield is crucial for estimating an aquifer’s ability to supply sustainable water resources.
In conclusion, various methods and techniques are used to gather essential information during borehole hydrological surveys. By combining resistivity and conductivity measurements with drilling and sampling techniques, as well as hydraulic testing, our hydrogeologists can develop a comprehensive understanding of the subsurface and its water-bearing properties, contributing to sustainable water management practices.
Data Collection and Analysis
Recording Borehole Logs
Borehole logs play a crucial role in hydrogeological surveys to understand the subsurface geology. Geologists record lithology, which describes the physical and mineralogical characteristics of rock formations. This information is vital to analyze groundwater storage and movement. In addition, accurate recording of porosity is essential, as it measures the volume of void spaces within the rocks that can store water.
During the logging process, geologists also collect samples of soil and rock at specific depths. These samples are then analyzed for their soil water content and moisture content, providing valuable insights into the hydrogeological properties of the subsurface materials. You can find more about borehole geophysical methods at the US EPA website.
Laboratory Analysis
Once the samples are collected, they undergo laboratory analysis to determine their chemical, physical, and mineralogical properties. This stage is crucial for assessing the groundwater quality and understanding how the subsurface water interacts with the surrounding environment. Some common tests performed during laboratory analysis include:
- Grain size distribution
- Porosity
- Permeability
- Soil water content
- Moisture content
These tests help to produce accurate and comprehensive data on subsurface materials, which is essential for a successful hydrogeological survey.
Data Interpretation
The final step in the data collection and analysis process is data interpretation. Geoscientists integrate the information obtained from borehole logs and laboratory analysis to create a comprehensive understanding of the subsurface hydrogeology. Data interpretation involves:
- Assessing the groundwater quality to determine the suitability of the water for various purposes, such as drinking, agriculture, or industrial uses.
- Developing a conceptual model of the groundwater flow system, including the direction and rate of groundwater movement.
- Estimating the amount of groundwater available for extraction, considering the balance between recharge and discharge.
- Analyzing potential impacts on the groundwater resource, including contamination risks and the effects of proposed groundwater management strategies.
By carefully interpreting the data collected during hydrogeological surveys, geoscientists help guide decision-makers in managing groundwater resources responsibly and effectively. You can find interesting examples of hydrogeological boreholes and their data interpretation in the British Geological Survey’s WellMaster hydrogeological database.
