Groundwater

Abstraction The act of removing water from a groundwater resource. The removal of water… Acid Mine Drainage (AMD) The generation of sulphate and acidity as a result of the oxidation of pyrite… Advection The process by which solutes are transported by the bulk movement of flowing… Allocable Groundwater The volume of groundwater available to allocate or distribute. Allocable… Alluvial Aquifer An aquifer comprising unconsolidated material deposited by water, typically… Anisotropy Having some physical property that varies with direction. Anisotropic… Aquatic Ecosystems Defined as the abiotic (physical and chemical) and biotic components,… Aquiclude A geologic formation, group of formations, or part of formation through which… Aquifer Aquifer means a geological formation which has structures or textures that… Aquifer System A heterogeneous body of intercalated permeable and less permeable material… Aquifer Testing Aquifer testing involves the withdrawal of measured quantities of water from… Aquifer Yield See Safe Yield Aquitard A saturated low permeability unit that can restrict the movement of… Artesian Aquifer See Confined Aquifer Note: Artesian is a term originally applied to boreholes… Artesian Borehole Boreholes that penetrate confined aquifers in which the piezometric surface… Artificial Recharge (AR) Recharge at a greater rate than natural recharge, resulting from deliberate… Assurance of Supply The reliability at which a specific quantity of water can be provided. The… Attenuation The breakdown or dilution of contaminated water as it passes through the… Augering The act of establishing a shallow borehole or wellpoint in unconsolidated or… Available Drawdown Available drawdown in a borehole is the difference between the static water… Available Yield This is the amount of water that can be expected to be 'available' for use…

Bank Storage Bank storage is water absorbed and stored by the soil pores of the bed and… Baseflow Sustained low flow in a river during dry or fair weather conditions, but not… Baseflow Index (BFI) The ratio of annual baseflow in a river to the total annual run-off. It is a… Basic Human Needs See Basic Water Supply Basic Water Supply Water Services Act Definition Basic water supply means the prescribed minimum… Basin See Catchment Blow Yield The volume of water per unit of time blown from the borehole during drilling.… Borehole Includes a well, excavation, or any other artificially constructed or… Borehole Casing A tubular lining of a borehole inserted to ensure borehole stability and… Borehole Log A record of the geological and hydrogeological conditions encountered in the… Borehole Testing Borehole testing is the process whereby a borehole is subjected to pumping… Borehole Yield Borehole yield is the volume of water that can be abstracted from a borehole.…

Capillary Fringe The area just above the water table in which water is held in the soil by… Capillary Zone See Capillary Fringe Catchment Catchment in relation to watercourse or watercourses or part of a… Catchment Management Strategy (CMS) A catchment management strategy is a framework for water resources management… Classification The classification system prescribed under the National Water Act (1998)… Coefficient of Storage See Storage Coefficient Conceptual Model A conceptual model includes designing and constructing equivalent but… Cone of Depression The depression of hydraulic head around a pumping borehole caused by the… Confined Aquifer A formation in which the groundwater is isolated from the atmosphere at the… Conjunctive Use Combined use of surface water and groundwater. Combined use of surface and… Connate Water Water entrapped in the interstices of sedimentary rocks at the time of… Contaminant Transport Model The application of a mathematical model to represent a regional or… Contamination The introduction of any substance into groundwater systems by the action of… Contamination Plume Area of degraded water in a stream or aquifer resulting from migration of a…

Dam A barrier built, usually across a watercourse, for impounding or diverting… Darcy's Law Darcy's Law states that the rate of flow through a porous medium is… Deficit A deficiency in amount. Describes the situation where the availability of… Degradable Pollutants These are those pollutants that can be broken down or reduced to acceptable… Density Matter measured as mass per unit volume (eg kilogram per cubic meter). The… Desired Ecological Status The future desired status of groundwater within the resource unit as used in… Detached Stream See Disconnected Stream Dewatering The process of abstracting groundwater to lower the water table and/or… Differentiated Protection Policy Sets of guiding principles and courses of action adopted or proposed by an… Diffusion The process by which ions or molecules move from areas of high solute… Dip Meter A device used to measure depth to groundwater. Dip meters are important tools… Discharge The net flow of subsurface water is directed toward the water table. A… Discharge Area That portion of catchment in which the net flow of subsurface water is… Discharge Rate The volume of water per unit of time abstracted from an aquifer system. The… Disconnected Stream A stream detached from and not in hydrological contact with the groundwater… Dispersion Spreading and mixing of chemical constituents in groundwater due to… Drain See Lateral Collector Drawdown The distance between the static water level and the surface of the cone of… Drilling The task of sinking a borehole into the subsurface using a drilling rig. The… Drilling Rig A term used to describe the equipment used to drill a borehole. A drilling… Drilling Techniques Different methods have been developed because of different geological… Dug Well A dug well is a shallow large diameter man-made pit or hole, from which… Dyke A tabular or sheet-like body of igneous rock that cuts through and across the…

Ecology The study of the interrelationships between organisms and their environment.… Ecoregions Regions within which there is a relative similarity in the mosaic of… Ecosystems An organic community of plants, animals and bacteria and the physical and… Effluent A liquid waste discharge , that discharges into the environment. Liquid waste… Effluent Stream A stream fed directly by groundwater; the surrounding water table or… Electrical Conductivity (EC) Electrical conductivity is a measure of how well a material accommodates the… Ephemeral Stream These streams are generally storm-event driven and flow occurs less than 20%… Estuary A partially or fully enclosed body of water, which is open to the sea… Evapotranspiration The loss of water from a land area through transpiration of plants and… Exploitation Potential The volume of harvest potential that can practically be exploited due to…

Fault A zone of displacement in rock formations resulting from forces of tension or… Feasibility Study The detailed analysis of a possible solution(s) described in the… Fissures An extensive crack, break, or fracture in rocks. A general term to include… Fitness for use Refers to water whose quality meets the requirements for a particular use.… Flow Nets Flow nets consist of two sets of lines. One set, referred to as equipotential… Flow Paths The subsurface course a water molecule or solute would follow in a given… Flow Regime A hydrological profile of a water resource. A river has a flow regime… Fluoride An ionic form of fluorine. Fluoride is a compound which occurs naturally in… Fluvial Of, or pertaining to, rivers; produced by river action. Relating to or… Formation A body of rock identified by lithic characteristics and stratigraphic… Fracture Any break in a rock including cracks, joints and faults. Cracks, joints or… Fracture Flow Water movement that occurs predominantly in fractures and fissures. Flow of… Fracture Zone A zone of fissures, fractures, cracks, joints and faults within rocks. A… Fractured Aquifer An aquifer that owes its water-bearing properties to fracturing. A fractured… Freshwater Water that contains less than 1000 mg/l salts. Water that contains only…

Gaining Stream See Effluent Stream Geohydrology The study of the properties, circulation and distribution of groundwater. In… Geology (Taken from Geological Atlas of Africa) Geology can be described as the complex structure of rock formations, which… Geomorphology The science that studies the nature and origin of landforms. The study of… Gradient See Hydraulic Gradient Groundwater Water found in the subsurface in the saturated zone below the water table.… Groundwater Allocation That volume of groundwater that can be allocated for use after consideration… Groundwater Divide The boundary between two groundwater basins which is represented by a high… Groundwater Flow Model The application of a mathematical model to represent a regional or… Groundwater Management Unit An area of a catchment that requires consistent management actions to… Groundwater Monitoring The regular or routine sampling, analysis and evaluation of one or more… Groundwater Resource All groundwater available for beneficial use, including man, aquatic… Groundwater Resource Unit A groundwater body that has been delineated or grouped into a single… Groundwater Unit See Groundwater Resource Unit

Harvest Potential The harvest potential is the maximum amount of groundwater that can be… Head See Hydraulic Head Heterogeneous Of dissimilar nature. Different in structure or composition throughout.… Homogeneous Of the same or similar nature. Uniform in structure or composition… Hydraulic Boundary Condition A mathematical statement specifying the dependent variable (e.g. hydraulic… Hydraulic Conductivity (K) Measure of the ease with which water will pass through the earth's material;… Hydraulic Gradient The rate of change in the total hydraulic head per unit distance of flow in a… Hydraulic Head Hydraulic head is the height above a datum plane such as sea level of the… Hydrodynamic Dispersion The process of diffusion cannot be separated from dispersion in flowing… Hydrogeology In South Africa the term geohydrology and hydrogeology are used… Hydrograph A graph which display specific hydrological measurements over time including… Hydrological Cycle The continuous circulation of water between oceans, the atmosphere and land.… Hydrological Year A continuous 12-month period from 1 October to 30 September. This is a period… Hydrology The study of the properties, circulation and distribution of water. Hydrology…

Infiltration The downward movement of water from the atmosphere into the ground.… Influent Stream An influent stream is positioned above the water table and discharges into… Interacting Stream See Intermittent Stream Interflow The rapid flow of water along essentially unsaturated flow paths, water that… Intergranular Aquifer A term used in the South African map series referring to aquifers in which… Intermittent Stream Rivers and streams whose interaction with groundwater depends on the… Interstices Openings or void spaces in a rock capable of holding water. Interstices are… Ionic Diffusion See Diffusion Isotopes Atoms of the same element having the same atomic number, but different mass… Isotropy The condition of having properties that are uniform in all directions.…

Juvenile Water Water formed through chemical reactions in geological processes and brought…

Karst Aquifer Limestone and dolomite areas that possess a topography peculiar to and…

Laminar Flow Water flow in which the stream lines remain distinct and in which the flow… Lateral Collector A lateral collector is a subsurface channel or piping system used to collect… Latrine A pit used for the disposal of human excreta, particularly prevalent in rural… Leachate Any liquid, including any suspended components in the liquid that has… Leaky Aquifer See Semi-confined Aquifer Lithology Lithology refers to the physical characteristics of rock. The physical… Losing Stream See Influent Stream

Major Aquifer System Highly permeable formations, usually with a known or probable presence of… Matrix A mass of fine grained and/or fractured rock, enclosing the main water… Matrix Diffusion The transfer of solutes from the main groundwater conduits to the surrounding… Mechanical Dispersion See Dispersion Meteoric Water Water originating from rainfall (usually recent) and actively involved in… Mine A mine can be defined as an excavation in the earth, from which substances… Minor Aquifer System These can be fractured or potentially fractured rocks which do not have a… Model Calibration Model calibration consists of changing values of model input parameters in an… Model Verification A calibrated model uses selected values of hydrogeologic parameters, sources… Molecular Diffusion See Diffusion Monitoring Borehole A borehole used to measure groundwater trends. A borehole at a selected… Multiphase Flow Two or more distinct phases of a compound or its breakdown products flowing…

National Water Act (NWA) A fundamental reform of the law relating to water resources; to repeal… National Water Resource Strategy (NWRS) The NWRS is mandated by the National Water Act, Act 36 of 1998, to describe… Nitrate Nitrate is chemical compound containing the nitrate (NO3) radical. Nitrate is… Non Aquifer System See Poor Aquifer System Non-perennial Stream See Ephemeral and Seasonal Streams. Non-Point Source Pollution Pollution from widely distributed sources instead of from a discrete or… Nonaqueous Phase Liquids (NAPLs) Organic compounds that do not dissolve readily in water. NAPLs do not readily…

Observation Borehole A borehole used to measure the response of the groundwater system to an… Opportunistic Irrigation Irrigation from run-of-river flow, farm dams, or compensation flows released… Osmosis Osmosis is the process where movement of water particles takes place through… Overland Flow See Runoff

Paleochannel A paleochannel is an old or ancient channel. Old or ancient river channels… Perched Aquifer Aquifers that contain perched groundwater i.e. bodies of groundwater… Perched Groundwater An independent and unconfined volume of groundwater separated from an… Percolation The process of the downward movement of water in the unsaturated zone under… Perennial Stream Streams where surface flow persists throughout the year. These streams are… Permeability (k) The ease with which a fluid can pass through a porous medium and is defined… pH pH is the negative logarithm of the hydrogen ion concentration in solution. A… Phreatic Zone See Saturated Zone Phreatophytes Plants that habitually obtain water from below the water table or from the… Piezometer A nonpumping borehole, generally of small diameter, for measuring the… Piezometric Surface An imaginary or hypothetical surface of the piezometric pressure or hydraulic… Point Source Pollution Pollution from discrete or definable points, as opposed to pollution from… Pollution Pollution means the direct or indirect alteration of the physical, chemical… Pollution Plume See Contamination Plume Pollution Source The origin or source of groundwater pollution. A pollution source is the… Poor Aquifer System These are formations with negligible permeability that are generally regarded… Pore Pressure The interstitial pressure of water within a mass of soil or rock. Pressure… Pore Space See interstices Porosity Porosity is the ratio of the volume of void space to the total volume of the… Porous Media A geological formation with voids or pore spaces within the porous texture… Potable Water Water that is safe and palatable for human use. Water that is drinkable and… Potentiometric Surface See Piezometric Surface Pre-feasibility Study A Pre-feasibility study focuses on the additional work that has been… Preferential Flow The preferential movement of water through more permeable zones in the… Primary Aquifer An aquifer in which groundwater moves through the original interstices of the… Pristine Remaining in a pure or natural state. Describes a water body remaining in a…

Quaternary Catchment A fourth order catchment in a hierarchal classification system in which a…

Recharge The addition of water to the saturated zone, either by the downward… Recharge Area An area over which recharge occurs. The area where water predominantly flows… Reconnaissance Study A desktop study of options available on a catchment scale to solve a water… Reliability of Supply See Assurance of Supply Remediation Reduce the concentrations of contaminants in groundwater to some acceptable… Remote Stream See Disconnected Stream Reserve Reserve means the quantity and quality of water required - a) to satisfy… Reservoir A natural or artificial unit used for the storage and regulation of water. A… Resource A resource is a substance or item available for use. A natural resource is a… Resource Directed Measures (RDM) This is a term used, but not defined by the National Water Act. The objective… Resource Quality This means the quality of all the aspects of a water resource including - -… Resource Quality Objectives (RQOs) This is a term used, but not defined by the National Water Act. Resource… Rest Water Level The groundwater level in a borehole not influenced by abstraction or… Riparian Habitat Area of land directly adjacent to a stream or river, influenced by… River A physical channel in which runoff will flow from higher to lower ground, and… River System A network of rivers ranging from streams to major rivers and, in some cases,… Rock Any mass of mineral matter, whether consolidated or not, which forms part of… Runoff All surface and subsurface flow from a catchment, but in practice refers to…

Safe Yield Safe yield is defined as the maximum rate of withdrawal that can be sustained… Saline Intrusion The replacement of fresh groundwater by saline water in an aquifer, usually… Salinisation The increase or accumulation of salt in the environment such as soil and… Salinity The concentration of dissolved inorganic salt in water. Total Dissolved… Saltwater Intrusion See Saline Intrusion Sanitation Means the prescribed minimum standard of services necessary for the safe,… Saturated Zone The subsurface zone below the water table where interstices are filled with… Screen A special type of casing, consisting of a slotted tube or wire wound tubular… Seasonal Stream These streams are driven by seasonal rainfall patterns and flow occurs… Secondary Aquifer An aquifer in which groundwater moves through secondary openings and… Semi-confined Aquifer An aquifer that is partly confined by layers of lower permeability material… Semi-unconfined Aquifer See semi-confined aquifer Significant Water Resource This is a term used, but not defined by the National Water Act. It relates to… Sill Sheet-like body of igneous rock which conforms to bedding or other structural… Sinkhole Sinkholes are subsidence or collapse features that form at points of local… Situation Assessment An assessment describing the status quo of groundwater related issues within… Soil The usually thin upper surface layer of the earth's crust comprising living… Soil Moisture The amount of water in unsaturated soil including water vapour, expressed as… Sole Source Aquifer An aquifer that is needed to supply 50% or more of the domestic water for a… Specific Capacity The rate of discharge from a borehole per unit of drawdown, usually expressed… Specific Storage (Ss) The volume of water that a unit volume of aquifer releases from or takes into… Specific Yield (S y ) The ratio of the volume of water that drains by gravity to that of the total… Spike See Wellpoint Spring A point where subsurface water emerges at surface, usually as a result of… Static Water Level See Rest Water Level Storage Coefficient (S) The volume of water an aquifer releases from or takes into storage per unit… Storativity (S) See Storage Coefficient Stream See River Subsurface Water All water occurring beneath the earth's surface, including soil moisture,… Sulphate A chemical compound containing the bivalent group SO4. Sulphate is an ion… Surface Water Bodies of water, snow or ice on or above the surface of the earth (such as… Sustainable Development Sustainable Development Use, development and protection of natural resources… Sustainable Yield See Safe Yield

Target Area A smaller area within a target zone with the potential for high yielding… Target Site A smaller area within a target area with the potential for high yielding… Target Zone A regional area, normally with regional geological structures where potential… Test Pumping See Aquifer Testing and Borehole Testing. Total Dissolved Solids (TDS) The quantity of dissolved materials in a sample of water. Total dissolved… Transboundary Aquifer System An aquifer system extending across more than one province or country. More… Transmissivity (T) Transmissivity is the rate at which water is transmitted through a unit width… Turbulent Flow Flow at velocities in which the stream lines become non-parallel and momentum…

Unconfined Aquifer An aquifer where the water table is the upper boundary and with no confining… Underground Water See Groundwater Unsaturated Zone That part of the geological stratum above the water table where interstices…

Vadose Zone See Unsaturated Zone Velocity Two types of groundwater velocities are of interest to geohydrologists: Darcy… Viscosity The intrinsic fluid property indicating the internal resistance to flow.… Vlei See Wetland Voids See Interstices Vulnerability The vulnerability of groundwater to contaminants generated by human…

Water Conservation Using water wisely and efficiently so that it is not wasted. The care,… Water Cycle See Hydrological Cycle Water Legislation Water law enacted by a legislative body. Laws/regulations to ensure the… Water Management Area (WMA) Water Management Area (WMA) is an area established as a management unit in… Water Resource Includes a water course, surface water, estuary or aquifer. [Source: National… Water Table The upper surface of the saturated zone of an unconfined aquifer at which… Water Table Aquifer See Unconfined Aquifer Water Transfers Water transferred from one catchment or basin to another. Water transfer is… Water Year See Hydrological Year Watercourse Watercourse means - a) a river or a spring; b) a natural channel is which… Watershed See Catchment Wellfield A group or cluster of boreholes in an area used collectively to supply… Wellpoint Shallow, small diameter hole used to abstract groundwater from primary… Wetland Land which is transitionary between terrestrial and aquatic systems, where… Windpump Wind-driven pump used to abstract groundwater. An air-lift pump that can lift…

Yield The amount of water from a borehole, aquifer or water resource within a…

Zone of Aeration See Unsaturated Zone Zone of Saturation See Saturated Zone