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General Terms Related to Groundwater
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| Artesian Well |
A well where natural pressure produces a constant supply of water to the surface without (or with very little) pumping. |
| Aquifer |
Underground layers of porous or fractured rock and soil that store and allow the passage of water. |
| Bore (Borehole) |
A hole in the ground used to locate groundwater which can be used to access water for sampling or use (in a groundwater monitoring context). |
| Drawdown |
The change in water table level in a well or aquifer, usually due to pumping and extraction of water from a well. |
| Monitoring Well |
A well that is used to take measurements relating to groundwater such as level, quality, flow-rate and more. |
| Permeability |
The ability of water to flow through a medium (soil) influenced by the spacing between and alignment of particles. Often measured as the rate (e.g. cm/h, mm/h, cm/day) that water can pass through the soil. |
| Plume |
The plume typically forms when pollutants enter the groundwater and start to spread out through the subsurface, following the flow of the groundwater. Understanding the extent and behaviour of a plume is critical for assessing the impact of the contamination and for planning remediation efforts. |
| Porosity |
Porosity in the context of groundwater refers to the space between particles such as soil, rock or sediment that can hold water or air. It is usually expressed as a percentage or a fraction. |
| Remediation |
Restoration of an environment to a less disturbed state by removing pollutants or taking other measures to reverse environmental damage. |
| Saturated/Unsaturated Zone |
The area where pores, fractures or other gaps underground in soil or rock are (or are not) filled with water. |
| Spring |
A point where groundwater naturally exits at the surface from an aquifer. |
| Wastewater |
Water that has been used or contaminated by human activities for some purpose (e.g. agricultural, industrial domestic) making it unsuitable for use without treatment. |
| Water Table |
The boundary between the underground saturated and unsaturated zones. |
Parameters Measured During Groundwater Monitoring
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| Dissolved Oxygen (DO) |
Denotes the free oxygen (not bonded with other compounds) in a water body. Expressed as the proportion of oxygen present compared to the maximal oxygen concentration at the temperature of the water (DO%). DO can be monitored using a specialised water quality meter such as the YSI ProSolo ODO Optical Dissolved Oxygen Meter. |
| Electrical Conductivity (EC) |
The ability of water to pass an electrical current. EC can indicate the presence contamination such as an excessive introduction of dissolved solid. |
| Flow Rate |
The rate water is moving. Measured as distance/time. |
| Oxygen-Reduction Potential (ORP) |
Indicates the presence of redox active species (strong reductants or oxidants). A high value can indicate that there is a large amount of dissolved oxygen. |
| pH |
A scale between 0 and 14 where values7 indicate a solution is alkaline (basic). The pH scale is a measure of the relative free hydrogen (H+) and hydroxyl (OH-) ions in a solution. Groundwater varies in pH depending on soil and rock type but can significantly affect the solubility and bioavailability of chemical constituents including both nutrients and contaminants. |
| Water Resitivity |
An indicator of the amount of dissolved salts (ions) in water, with higher resistivity indicating a lower presence of salts and vice versa. Specifically, resistivity is the ability of water to resist an electrical current. |
| Salinity |
A direct measurement of the dissolved salt concentration of water. Salinity is a critical parameter in water chemistry that affects the suitability of water for drinking, irrigation, and industrial uses, as well as the health of aquatic ecosystems. |
| Total Dissolved Solids (TDS) |
Combined measurement of all dissolved substances in water, both organic and inorganic. |
| Total Organic Carbon (TOC) |
The total amount/concentration of all organic carbon compounds in water. |
| Total Suspended Soilds (TSS) |
The total amount/concentration of non-dissolved suspended particles, commonly measured in mg/L. |
| Turbidity |
The clarity of water, indicating the presence of suspended solids, organic compounds and more. Measured in nephelometric turbidity units (NTU). |
Groundwater Monitoring Equipment
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| Bailer |
A type of grab sampler used to retrieve a water sample from a groundwater monitoring well. Bailers generally consist of a hollow tube tethered to a cord which allows the bailer to be lowered into the well and retrieved. |
| Bladder Pump |
A type of pump used to collect groundwater samples that consists of a long tube with a ‘bladder’ on one end that sits in the water and creates a partial vacuum allowing water to be transported up the tube so that samples can be collected for analysis. |
| Controller |
A pump controller is a device that manages the operation of a groundwater pump to ensure efficient and reliable water delivery. In general, they regulate when the pump turns on and off based on water demand and pressure levels, monitors groundwater levels to prevent the pump from running dry and adjusts the pump’s speed to match the required water flow. |
| Interface Meter |
A device that measures the depth and thickness of oil and water layers. Geotech’s Interface Meters do this using dual sensor technology that distinguishes hydrocarbons from conductive fluid layers. |
| Multiparameter Instrument |
A type of water quality meter that is capable of measuring multiple groundwater parameters and quality indicators. For example, the YSI ProDSS Digital Sampling System Water Quality Meter measures pH, DO, conductivity, turbidity, ORP and temperature. |
| Peristaltic Pump |
Pumps that create a vacuum by compressing the tube, continuously pulling water from the well and squeezing it along the tube for the sampling period. Peristaltic pumps are particularly advantageous for groundwater sampling due to their versatility and that the fluid only comes in contact with the tube, rather than the pump itself, avoiding potential contamination. They are best suited to sampling shallow wells below ~8m. |
| Submersible Pump |
Pumps that are fully submerged during use, providing high efficiency, self-priming capability and the ability to conduct purging at a high flow rate as well as low flow sampling. Most submersible pumps such as the Fultz 12V Electric Submersible Pump allow the user to control the flow rate and can continuously sample over an extended period of time. |
| Water Level Meter |
Accurately measure the depth/water level of wells, boreholes and standpipes. Water level data is essential to monitor how groundwater reserves change over time, particularly when significant amounts are being extracted for human-use. |
| Turbidity Meter (Nephelometer) |
An instrument that measures turbidity by emitting light through a sample and measuring the amount of that light scattered by the particles in the sample. |
| Water Quality Consumables |
Items used in conjunction with groundwater monitoring equipment to complete sampling. Some examples of water quality consumables are filters, decontamination and calibration solutions, HydraSleeve’s (disposable no-purge grab samplers), bladders, tubing and more that are used during water quality sampling and disposed of after use. |
Groundwater Sampling Methods and Processes
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| Deep Well Monitoring |
Where samples need to be collected from a greater depth than usual, specialised sampling equipment may be required. Instruments that are capable of sampling deep wells may have longer tubing or be able to operate effectively under higher levels of pressure. A Deep Well Monitoring Kit allows for sampling of greater depths than most pumps alone can achieve with an optional drop tube assembly that can be used to sample below the specified maximum sampling depth. |
| Leachate |
A solution that is the product of leaching. In a water monitoring context, the term is generally used to describe water that has been contaminated as it has percolated through a landfill or other waste disposal site. |
| Low-Flow Groundwater Sampling |
Purging and sampling wells at a rate closer to the natural flow of groundwater (usually less than 500ml/min). Low-flow sampling is generally the preferred method of sampling as it makes obtaining a representative sample more likely, reduces waste from purging, minimises turbulence and lowers potential for drawdown. A low flow pump such as the Sample Pro Portable MicroPurge Pump is commonly used to conduct low flow sampling. |
| Purging |
Moving stagnant water from a well prior to sampling, in order to obtain a representative sample of actual aquifer conditions. |
| Representitive Sample |
A sample that contains the constituents of the water body in proportions that are close to or the same as the wider water body. |
Common Groundwater Contaminants
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| Hydrocarbons |
Organic compounds consisting of hydrogen and carbon. They are the main constituents of fossil fuels (like natural gas, petroleum, coal) and commonly contaminate groundwater due to their extraction and storage. Due to the hydrophobicity of hydrocarbons, they are not soluble in water and persist for long periods of time making them difficult to remove. Water contaminated by hydrocarbons can be toxic. |
| PFAS (Per-fluoroalkyl substances) |
These substances have been widely used since ~1940s and due to their inert nature, breakdown very slowly in the environment. Due to their persistence and abundant use, PFAS are found in the air, soils, water, animals, fish and even humans all around the world. PFAS are often used in plastics and are therefore found in many types of water sampling equipment. When conducting sampling that may contain PFAS, it is important to ensure the equipment used is PFAS free to record accurate results that are unaffected by the instrumentation used to collect the sample. |
| NAPLs (Non-aqueous phase liquids) |
Refers to hydrocarbons (mainly fuels such as petroleum, gasoline and diesel) that contaminate groundwater and soils and are generally insoluble in water. Can be dense (DNAPL) or light (LNAPL), with DNAPLs generally sitting at the bottom of aquifers when they encounter a low permeability layer whereas LNAPLs sit atop the water table. Due to these characteristics, LNAPLs are easier to remediate whereas DNAPLs are more challenging to remove. |
| VOCs (Volatile Organic Compounds) |
Volatile organic compounds (VOCs) are organic compounds that readily evaporate at room temperature. The group of compounds includes a wide range of organic substances encountered by people every day, including products such as paints, cleaning agents, petroleum fuels and more. Some VOC’s that are commonly found contaminating groundwater include trichloromethane (chloroform), solvents such as tetrachloroethylene as well as gasoline hydrocarbons and oxygenates. |
