Hydrogeology Flashcards
Area of Influence
The area within which the potentiometric surface is lowered by withdrawal or raised by injection of water through a well
Aquifer
A geologic unit that is saturated and sufficiently permeable to transmit significant economic quantities of water to wells and springs
capillary fringe
The lowest part of the zone of aeration, immediately above the water table, where water is under pressure that is less than atmospheric pressure
Cone of depression
A depression in the potentiometric surface of ground water that has the shape of an inverted cone and develops around a well from which water is being withdrawn. It defines the area of influence of a well.
connate water
water trapped in the pores of a sedimentary rock at the time of deposition; fossil water
Darcy
A unit of intrinsic permeability = 9.87 * 10e-9 cm2
Darcy’s Law
Q = KiA
Effective porosity
The percentage of the total volume of a soil or rock that consists of interconnected pore space. The term is sometimes used analogously to specific yield.
Field Capacity
The quantity of water held by the soil or rock against the pull of gravity. Field capacity is dependent on the length of the time the soil or rock has been undergoing gravity drainage, while specific retention is not.
Flow Net
two-dimensional representation of flow lines and equipotentials
head
a measure of the potential energy of a fluid at any given point with respect to a given datum. In practice, it is the elevation to which water rises at a given point as a result of reservoir pressure.
Hydraulic conductivity
the capacity of a porous medium to transmit water. units are L/T
hydraulic gradient (i)
rate of change in total head per unit of distance of flow in a given direction
intrinsic permeability (ki)
a property of the porous medium that measures the relative ease with which a fluid can be transmitted through it under a hydraulic gradient. It is dependent upon the pore size and measured in darcys.
Juvenile water
water that is derived directly from magma and is thought to have come to earth’s surface for the first time
Meinzer
a unit of hydraulic conductivity in gpd/ft2. Rate of flow in gallons per day through a cross-section of one square foot under a hydraulic gradient at 60F
Packer Test
An aquifer test in which two inflatablwe seals (or packers) are set in an open borehole to prevent movement of groundwater in the test section while the permeability of the isolated rock is determined.
Perched groundwater
unconfined groundwater separated from an underlying body of groundwater by an unsaturated zone
Percolation test
A test made by digging a hole, filling it with water, and measuring the decline of the water level.
Permeability
The property of a porous rock or soil for transmitting a fluid. It measures the relative ease of flow under unequal pressure.
Potentiometric surface
A surface that represents the total head of groundwater and is defined by the level to which water will rise in a well
Runoff (R)
The part of precipitation appearing in surface streams
slug test
an aquifer test where you pour a small charge of water into a well or where you remove a slug of water from the well. The removal of water from the well is also called a bail-down test
Specific retention (St)
Ratio of the volume of water a soil or rock can retain against gravity drainage to the total volume of the soil or rock, usually stated as a percentage.
