Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
50 Cards in this Set
- Front
- Back
|
Groundwater Profile
|
Vadose Zone
Zone of saturation Water Table |
|
|
Vadose Zone
|
Groundwater profile
Unsaturated zone |
|
|
Water Table
|
Groundwater profile
The upper boundary of the vadose and saturation zones |
|
|
Rate of infiltration
|
function of soil type, rock type, antecedent water, and time
|
|
|
Capillary fringe
|
a layer of variable thickness that directly overlies the water table. Water is drawn up into this layer by capillary action
|
|
|
Water basin with sandstone
|
lower runoff potential and lower drainage density
|
|
|
Water basin underlain by shale
|
High runoff potential and greater drainage density
|
|
|
Aquifer
|
a formation that allows water ti be accessible at a usable rate.
Permeable layers such as sand,gravel, and fractured rock |
|
|
Unconfined aquifer
|
no confining layers that retard vertical water movement
|
|
|
Artesian well
|
develops from high pressure in a confined aquifer
|
|
|
Water is ____ through aquifer systems
|
continually recycled
|
|
|
Groundwater recharge
|
any water added to the aquifer zone
|
|
|
Processes that contribute to groundwater recharge
|
precipitation, streamflow, leakage (resevoirs, lakes, aqueducts), and artificial means (injection wells)
|
|
|
Groundwater discharge
|
any process that removes water from an aquifer system such as natural springs and artificial wells
|
|
|
Groundwater supplies ____ of the water present in our streams
|
30%
|
|
|
Effluent streams
|
act as discharge zones for groundwater during dry seasons
|
|
|
Base flow
|
phenomenon of effluent streams
|
|
|
Groundwater overdraft
|
reduces the base flow, which results in the reduction of water supplied to our streams
|
|
|
Recharge zone
|
area where water infiltrates downward from surface to GW
|
|
|
Discharge zone
|
Area where water is removed from an aquifer, such as a spring, well, river, etc.
|
|
|
Gaining stream
|
stream receives flow from the groundwater aquifers - common in eastern USA where precipitation is high
|
|
|
Losing stream
|
river feeds the groundwater and replenishes the aquifer - common in arid areas where rivers run dry between storms
|
|
|
hydraulic gradient
|
the gradient of the water table, generally following the topographic gradient
|
|
|
hydraulic conductivity
|
ability of rock materials to allow water to move through (m^3/day/m^2)
|
|
|
well sorted course (sand-gravel)
|
high permeability
|
|
|
poorly sorted coarse-fine
|
medium permeability
|
|
|
well sorted fine )silt-clay)
|
low permeability
|
|
|
Porosity
|
percentage of void (empty) space in sediment or rock to store water
|
|
|
Permeability
|
measuring the interconnection of pores in a rock material
|
|
|
groundwater movement: water table
|
sloping surface
|
|
|
slope/gradient
|
determined by the difference in water table elevation (h) over a specified distance (L)
|
|
|
Direction of flow
|
downslope
|
|
|
Flow rate
|
depends on the gradient and the properties of the aquifer
|
|
|
Hydraulic head
|
the driving force that moves groundwater.
Used to determine hydraulic gradient |
|
|
Water moves from from an area of ____ hydraulic head to an area of ____ hydraulic head. Therefore groundwater flows _____, _______,or _______
|
higher
lower downward, laterally, or upward |
|
|
Hydraulic gradient for unconfined aquifer
|
approximately the slope of the water table
|
|
|
Hydraulic conductiity
|
ability of material to allow water to move through it, expressed in terms of m/day (distance/time). It is a funtion of the size and shape of particles, and the size, shape, and connectivity of pore spaces
|
|
|
Darcy's Law
|
indicates the rate at which water will flow in the ground.
Q=-KA delta H / delta L |
|
|
Q
|
Flow rate
|
|
|
K
|
hydraulic conductivity (high for permeable sediments like sand or gravel, low for clay)
|
|
|
A
|
cross-sectional area of aquifer. Usually per unit
|
|
|
delta H
|
change in hydraulic head (a measure of pressure differences)
|
|
|
delta L
|
change in distance
|
|
|
delta H / delta L
|
taken together give the gradient
|
|
|
Pumping well can create...
|
cone of depression and reverse natural directions of groundwater flow
|
|
|
Overpumping has two effects
|
1. changes the groundwater flow
2. lowers the water table, making it necessary to dig a deeper well |
|
|
lowering of water table leads to
|
desertification in some areas, original land users and owners often spend lots of money to drill new deeper wells, streams become permanently dry
|
|
|
Available groundwater
|
estimated aboe the total flow of the Mississippi during the last 200 years
|
|
|
GW as primary drinking water source for ___ of the US popular
|
50%
|
|
|
GW overdraft problems
|
extraction rate exceeding recharging rate
|
