Glossary

• Active Porosity - percentage of water that drains by gravity or "specific yield."

• Anistrophic - a formation is anistropic at a point if the hydraulic conductivity K varies with the direction of the measurement. [2]

• Aquifer - formation or group of saturated geologic formations capable of storing and yielding freshwater in usuable quantities, formed from rocks or soils or both.

• Aquifer Conditions -
  • Unconfined
    • receive recharge directly from the overlying surface
    • shallow water level
    • water at atmospheric pressure at water table
    • other names- water table, ordinary or gravitational
  • Confined
    • bounded below and above by aquitards
    • does not receive significant amounts of percolation from the overlying surface
    • under a pressure that includes the sum of the weight of the atmosphere and the overburden
    • unconfined at their exposed edges
    • other names - artesian or potentiometric aquifers
• Aquitard - semi-confining beds that allow a very slow flow of water through them. The total volume of water might be large though if the aquitard itself is large.

• Capillary Fringe - lower boundary of the vadose zone where the soil pores are completely filled with water.
  Note: Coarse grained mediums with large pore spaces and a low ratio of surface area to volume have little or no capillary fringe, while fine particle mediums with small pore spaces and a large surface area to volume ratio may have capillary fringes of 50 feet or more.

• Cone of Depression - potentiometric or gravity free pressure surface that extends radially outward from the well and is a function of storativity, transmissivity, the pumping rate of the well and time.

• Confining Beds - beds that do not allow the easy penetration of water across them.

• Continuity Equation - is given as the mass of fluid flowing into a given volume is equal to the mass of fluid flowing out of the volume.

• Density - of a fluid is defined as its mass per unit volume.

• Drawdown - value of the groundwater potential below an arbitrary datum.

• Effective Porosity - a portion of the total porosity or interconnected void space that is available for groundwater flow.

• Evapotranspiration - the processes of evaporation and transpiration.

• Groundwater - subsurface water that occurs beneath the water table in soils and geological formations that are fully saturated.

• Hydraulic Conductivity - constant of proportionality in Darcy' Law which is a function of the medium through which the fluid flows as well as the properties of the fluid.

• Hydraulic Diffusivity(D) - defined as

  

  or

  

• Hydraulic Gradient - change in hydraulic head with respect to the change in the length of the path.

• Hydraulic Head - potential water levels.

• Hydrologic Cycle - the continuous circulation of water between the oceans, the atmosphere and the land.

• Infiltration Capacity - Maximum rate at which a soil can absorb water. The capacity is a limiting curve that describes the maximum possible rates of infiltration as a function of time.

• Isotropic - a formation is isotropic at a point if the hydraulic conductivity K does not vary with the direction of the measurement.

• Laminar flow - on a macroscopic view, a very smooth or orderly flow

• Leakage - vertical seepage across the boundaries which is determined by calculation of Darcy's Law.

• Manometers - a tube or pipe used to determine the elevation of a water level. In the field this device is called a piezometer.

• Phreatic Surface - the water table surface or the level at which water stands. Also the upper boundary of an unconfined aquifer.

• Phreatic Zone - zone of saturation.

• Piezometer - a tube or pipe used to determine the elevation of a water level. In the laboratory this device is called a manometer.

• Piezometric Surface - the surface created in a contour plot of the different elevations of water levels sampled in the investigation of a well site.

• Porosity - is simply the volume of the voids between the grains in the medium.
  • Active porosity - the specific yeild or the percentage of water that drains by the force of gravity.

  • Effective Porosity - is the portion of ithe total interconnected pore space through which water flows. Not all interconnected pore space allows the flow of water.
  • 3 Major types
    1. - spaces between the grains which is primary porosity or the void spaces formed as the medium is deposited
    2. - fractures or secondary porosity void spaces created through structural deformation and erosion
    3. - tubes through which the water flows

• Pores - the void spaces between the grains of a porous medium.

• Porous Medium - solid material with interconnecting void spaces.

• Storativity - addition or release of water to the storage space due to the increase or decrease of hydraulic head. Storativity is a function of the thickness of the saturated aquifer and the Hydraulic Conductivity.

• Streamline - path followed by a sequence of water particles.
  • Laminar flow - on a macroscopic view, a very smooth or orderly flow.
  • Turbulent flow - irregular or rotational flow paths such as those found in rivers and streams.

• Surface Retention - process where electrical forces bind water molecules to grain surfaces in the vadose zone and the capillary fringe where pressures are less than atmospheric.

• Transmissivity - a function of the hydraulic conductivity and the thickness of the aquifer and descibes how easily the aquifer moves groundwater through its pore spaces.

• Turbulent flow - irregular or rotational flow paths such as those found in rivers and streams.

• Vadose Zone - first layer under the ground level and above the water table where the soil pores are only partially filled with water and the fluid pressure is less than atmospheric.

• Viscosity - property that allow fluids to resist relative motion and shear deformation during flow.[2]

• Watertable - phreatic surface - upper boundary of an unconfined aquifer.