GEOSCIENCE AND ENVIRONMENTAL SERVICES

Groundwater Resource Development and Management

Case Study – Groundwater Resource Development and Management

All over the world, groundwater resource has become an invaluable resource for socio-economic development. It is a primary source for drinking water, industrial and agricultural development. MEK staff have been involved in groundwater resource development and management in various parts of the world and thoroughly understands the inherent challenges and effective and technical solutions to address most of these problems.

Groundwater Resource Development

We have the expertise and technical know-how to select, drill, design and construct prolific and sustainable water well sites in igneous, sedimentary and metamorphic terrains. We have used different tools in well site selection and we are guided by our understanding of the hydrogeology that is derived from our terrain assessment studies. In very difficult hydrogeological terrains we derived information from satellite imageries to help home in on areas with high potential for groundwater. Once these areas are located on the ground, we refine the likely locations of aquifers using our structural geological knowledge of the area together with geophysical techniques to select prospective well sites.  Using this methodology, our team has consistently realized increments of between 20 to 85 percent in well drilling success rate when our drilling results are compared to other drilling campaign results in the same or similar difficult hydrogeological terrains. Additionally, our approach has resulted in much higher water well yields. We have been involved in the completion of well over 1,000 water wells in different parts of the world, ranging from shallow hand-dug domestic and community water wells to high yielding municipal and industrial water wells.

Our water wells are designed based on information derived from well logs, sieve analysis results, pumping and aquifer test data, water chemistry and the anticipated water demand. Additionally, factors that will enhance well efficiency, reduced operational cost and ensure the long-term sustainability of the wells are taken into consideration in the well design and construction.

The company has the expertise and the state-of-the-art facilities to embark on full-scale groundwater exploration and development activities for individual homes (domestic), rural water supply programs (districts/county), and for commercial and industrial purposes for our clients.

Our water well drilling campaign is carried out in the following chronological order:

  • Review of available geological and hydrogeological literature on terrain conditions and previous drilling campaigns, if any;
  • Analysis and interpretation of remotely sensed data (processed satellite imagery) and stereo aerial photographs;
  • Terrain evaluation;
  • Geophysical surveys and interpretation of results;
  • Drilling of Well
  • Sieve Analysis
  • Well Design and Construction;
  • Well Development;
  • Well Chlorination;
  • Pumping and Aquifer tests; and
  • Pump Installation.

Additionally we have vast experience and the technical know-how in the construction of hand-dug wells in loose and highly weathered to semi-consolidated rock formations. We have constructed over hundreds of hand-dug wells; lined them with concrete rings and/or PVC plastic sheets, some to depths in excess of 20 meters (Plate 8).

Our service consists of:

  • Selection of the most favourable well sites
  • Digging of the wells
  • Lining of the excavated wells through the lowering of concrete rings
  • Back-filling of the annular space between the concrete rings and the well’s natural embankment with sand
  • Conduction of water-quality tests
  • Chlorination of the wells
  • Covering the wells with concrete slabs
  • Construction of aprons and drainage gutters around wells
  • Installation of pumps on completed wells.

Groundwater Resources Management

The main purpose of groundwater resource management is to limit the adverse impacts of severe abstraction and contaminant loads. This can be realized by continuously monitoring the well’s response and water quality over the long run. Effective groundwater management should ensure the quantity and quality required for domestic, commercial, industrial, agricultural and environmental usage is not compromised. Furthermore groundwater resource management is necessary to prevent land subsidence of both private and public infrastructures.

In general, groundwater monitoring data can be used to estimate the amount of groundwater that can safely be withdrawn from an aquifer without severe environmental impacts. Information obtained from groundwater level can also be useful in forestalling severe decline in groundwater levels that may arise from acute abstraction. This could ultimately lead to prohibitive cost of providing potable water and even have adverse impacts on groundwater quality. Furthermore groundwater level data can be very helpful in establishing the interaction between surface and groundwater systems.

Our hydrogeologists have excellent experience in the entire spectrum of groundwater resources management, which can be broken into main categories: groundwater level monitoring and groundwater quality monitoring.

Groundwater Level Monitoring

Primary Groundwater Monitoring
In primary groundwater monitoring, the focus is to analyze trends in groundwater water levels due to land-use and climatic changes and also to changes in recharges, flows and diffuse contamination.

Secondary Groundwater Monitoring
In secondary groundwater monitoring, MEK focuses on the protection of groundwater resources, wellfields, land subsidence and the protection of groundwater–depended ecosystems against potential environmental impacts.

Tertiary Groundwater Monitoring
For tertiary groundwater monitoring MEK is concerned with providing early warning of adverse environmental impacts on groundwater resources that can arise from intensive agricultural land use, industrial and mining activities and disposal of waste (landfill).

Continuous groundwater level monitoring is required to ensure reliable supply and also protect quality. In developing an effective groundwater monitoring network, the MEK team will carefully analyze and evaluate the geological, hydrogeological, and land and water use settings carefully before selecting the location of monitoring wells. Furthermore, we will carefully consider trends in land and water uses in residential, industrial, agricultural and environmental settings and incorporate our findings into the final monitoring program designs.

From the groundwater level data, our Hydrogeologist will develop two- and three-dimensional groundwater flow models clearly showing the groundwater flow patterns, recharge and discharge zones within the monitored region. Furthermore, using multi-temporal groundwater level data, our team is able to accurately predict seasonal and long-term changes in the groundwater flow patterns over an entire region.

Groundwater Quality Monitoring

Because water is a good solvent, it can easily become contaminated due to dissolution of one or of several contaminants.  Groundwater contamination is usually due to one of the following:

  • Contamination from naturally occurring chemicals in soil and rock formation e.g., dissolution of naturally occurring toxic arsenic and selenium in rocks;
  • Contamination as a result of agricultural, commercial and industrial activities; and
  • Leakage from Underground Storage Tanks into the soil and groundwater systems.

MEK has a full-fledged groundwater sampling protocol tailored in line with the World Health Organization and Canadian Environmental Protection Agency protocols. The protocol contains quality control/quality assurance (QA/QC) measures to ensure that water samples from the field submitted to the laboratory are representative of the sampled groundwater. This implies that groundwater samples are stored in the appropriate containers together with other QA/QC samples under approved temperature conditions and submitted in a timely manner to an accredited laboratory for analysis.

Upon receipt of the laboratory analytical results, MEK staff will perform an in-house due diligence by analyzing laboratory analytical results to affirm their accuracy and precision.

From the laboratory results MEK is able to determine spatial variation in groundwater quality over the monitored area. Long-term spatial variations in water quality are determined from multi-temporal groundwater quality data. This latter analysis will also enable our staff to affirm the encroachment or mobility of pollutants into the aquifer of interest.

Wellhead Protection Studies

On-going activities within a wellhead protection area have the potential to affect the water quality entering the well and as such the need to delineate the wellhead protection area and take steps to protect it. The major potential sources of contaminants are usually the following:

  • Non-point sources such as spills areas of fertilizers and pesticides;
  • Landfills;
  • Septic tanks and sewerage systems;
  • Underground and above ground storage tanks;
  • Animal feedlots; and
  • Chemical Storage facilities.

The areal extent of the wellhead protection area is determined by several factors including the general topography of the land surface, the aquifer type, direction and velocity of groundwater flow; the overlying soil around the well and the water extraction rate, among others.

To ensure the integrity of the aquifer (groundwater body) and prevent its pollution, a Wellhead Protection Plan (WHPP) must be developed. The ultimate goal of protecting the WHPP is to protect public health. In general, the WHPP will reduce the risk of contaminating the groundwater resource and therefore ensuring the long-term supply of potable water. It will also help reduce water treatment costs. MEK has the tools and technical know-how to help accurately delineate the WHPP area. Our team is experienced in using the techniques listed below to accurately delineate WHPP, the capture zone and the contributing areas to the pumping well upon which a WHPP can be based. Over the years our professional staff have used, among others, the following techniques in delineating WHPA:

  • Arbitrary Fixed Radius (AFR) technique;
  • Calculated Fixed Radius (CFR);
  • Analytical Equations;
  • Hydrogeological Mapping; and
  • Numerical Flow Modelling

MEK will be pleased to work with you to delineate your WHPP area and assist you in developing a comprehensive and an effective WHPP plan for your wellhead.

Aquifer Simulation and Modelling

Groundwater models are necessary for understanding the behaviours of groundwater systems in a specific manner and to predict the aquifer behaviour under changing hydrogeological conditions. In the broadest sense a “groundwater model” is the sum of the components, physical or otherwise used to describe a groundwater system. In other words, it is the representation of the construction and working of an aquifer systems of interest. The model will be similar to but simpler than the aquifer systems but a close approximation to the aquifer it represents. On the other hand simulation is a tool to assess the performance of the aquifer under existing, planned or anticipated changing hydrogeological conditions.

MEK generally  uses groundwater models for the following studies:

  • Conceptualization and quantification of hydrogeological conditions of aquifer systems and using the information to plan future data requirements;
  • Exploration of groundwater system dynamics such as surface water-groundwater interactions, recharge areas, seepage rates, transportation dynamics etc.
  • Prediction of changes in aquifer behaviour likely to result from anticipated changes in water abstraction rates;
  • Identification of wellhead protection areas and capture zones;
  • Designing and refining existing monitoring wells networks to better understand the behaviour of the aquifer under changing hydrogeological conditions;
  • Evaluating mitigation options for remediation planning; and
  • As a management tool in the management of complex and extensive aquifer systems.

MEK staff have used analytical, numerical and stochastic models over the years to address numerous challenging groundwater flow and contaminant fate and transport problems in porous and fractured media in different hydrogeological terrains. Our team has developed numerous (finite difference and finite element)  groundwater flow and solute transport models to conducts studies related to leachate movement from landfills, saltwater intrusions, contaminant movement from seepage ponds and movement of pesticides from agricultural fields.

The MEK groundwater modelling team will be pleased to assist you with its expertise to find sound and professional solutions to address your groundwater management problems.

Case Study – Groundwater Resource Development and Management