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(8)
(8) Groundwater and Wells
| Question | Answer |
|---|---|
| Aeration Zone (Vadose Zone/Unsaturated Zone) | The voids in the soil contain some air. |
| Saturation Zone (Phreatic Zone) | Lies below the aeration zone. The voids in the soil are completely filled with water. |
| Aeration Zone: Subzone | Soil-water zone |
| Aeration Zone: Subzone | Intermediate Zone |
| Aeration Zone: Subzone | Capillary Zone |
| Soil-Water Zone | The uppermost zone and is typically 3 to 10 feet thick. |
| Field Capacity (Specific Retention) | Describes the maximum equilibrium moisture content, where gravity drainage becomes negligible. |
| Intermediate Zone | Is below the soil-water zone and above the capillary zone. |
| Capillary Zone (Tension-Saturated Zone/Capillary Fringe) | A relatively thin zone located below the intermediate zone. Water is pulled upward from the water table by capillary force, saturating a layer of soil above the water table. |
| Aquifer | Is a geologic formation that can store and transmit water in significant quantities. |
| Aquicludes | Store water, but they cannot transmit water in significant amounts. |
| Aquifuges | Neither store nor transmit water |
| Unconfined Aquifers | Are not completely enclosed by impermeable layers, which allows then to interact with the atmosphere. |
| Confined Aquifers | Are completely enclosed by impermeable layers, which isolates them from atmospheric interaction. |
| Aquifer Porosity | The proportion of void spaces within soils or rocks |
| Hydraulic Gradient | The change in hydraulic head over distance that drives groundwater flow. |
| Artesian Well | When a well penetrates a confined aquifer where the hydrostatic pressure head is greater than the ground elevation, the water rises in the well and may flow to the surface without pumping. |
| Volumetric Moisture Content | Is a ratio of the volume of water in a soil sample relative to the total volume of the soil sample. |
| Gravimetric Moisture Content | Is the ratio of the mass in a soil sample to the mass of the dried sample |
| Specific Storage | Indicates how much water a confined aquifer can release or absorb in response to changes in pressure |
| Specific Yield | Is a dimensionless value that represents the volume of water that can drain from an aquifer under the influence of gravity |
| Storativity (Coefficient of Storage) | Is a dimensionless value that measures how much water an aquifer releases when the hydraulic head in the aquifer is lowerd. |
| Specific Discharge (Specific Capacity, Darcy Flow, Darcy Velocity) | Is a measure of the flow rate of water per unit width of the aquifer. |
| Specific Retention | The amount of water retained in the pore spaces of an aquifer that cannot be drained by gravity. |
| Hydraulic Head | The total mechanical energy per unit weight of water at a specific location. |
| Hydraulic Gradient | Measure of the change of pressure head per unit length over the aquifer length |
| Equipotential Lines | Lines of equal hydraulic head |
| Flow Lines | Show the actual direction of movement |
| Geohydrology | Emphasizes hydrological factors |
| Hydrogeology | Emphasizes geological factors |
| Hydraulic Fracturing (Fracking) | Water under high pressure is injected deep shale formations to facilitate the extraction of natural gas, and the residual water used in the process has the potential to contaminate surrounding water supplies. |
| Hydraulic Budget | Which tracks all the inflows, outlaws, and changes in storage within a groundwater system. |
| Infiltration | The primary contributor to groundwater recharge |
| Hydraulic Conductivity (Permeability) | The rate at which water moves through soil under a hydraulic gradient, influenced by both soil's characteristics and the fluid's properties. |
| Steady-State Flow | Implies that flow conditions remain constant over time. |
| Two-Dimensional Flow | Assumes that changes in the flow field occur primarily radially and vertically, resulting in the formation of a cone of depression around the well. |
| Drawdown | Any decline in the water level |
| Homogenous | Composed of uniform soil material |
| Isotropic | Having constant physical properties |
| Aquifer Loss | Results from the flow of water through the surrounding porous medium toward the well. |
| Well Loss | Results from inefficiencies in the flow of water within and near the well. |
| Specific Capacity | The pumping rate per unit of drawdown |
| Well Efficiency | Measures how effectively a well converts pumping effort into water yield with minimal drawdown, indicating the well's ability to deliver water with low resistance flow |
| Unconfined Aquifer | If water only partially fills the aquifer materials and is free to rise and fall along the unsaturated/saturated zone boundary |
| Confined Aquifer (Artesian Aquifer) | Is trapped below a layer of less permeable or impermeable rock and is normally filled with water. |
| Aquitard | Is a layer that does not transmit water easily |
| Aquiclude | Is a layer that does not transmit water at all |
| Potentiometric Surface | Is an imaginary surface that defines the level to which water in a confined aquifer would rise were it completely pierced with wells. |
| Transmissivity | Defined as the volume of water per day that flows laterally through a 1-ft-wide (or 1-m-wide) strip extending the height of the aquifer under a 1 ft/ft (1 m/m) hydraulic gradient |
| Total Porosity | The volume of water that is lost, when the volume of aquifer material within the saturated zone is completely dried. |
| Effective Porosity | The volume of pore spaces that will drain in an reasonable period of time by gravity |
| Drawdown | The reduction in hydraulic head (either water surface or pressure) observed at a well an aquifer. |
| Well Loss | The difference between the head in the aquifer immediately outside the well and the head inside of the well |
| Well Efficiency | The ratio between theoretical drawdown and the actual drawdown measured in the well |
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user-1997879