Water – Supply & Use. Groundwater –Vadose zone (formerly known as the unsaturated zone) –Zone...
-
Upload
delphia-neal -
Category
Documents
-
view
214 -
download
1
Transcript of Water – Supply & Use. Groundwater –Vadose zone (formerly known as the unsaturated zone) –Zone...
Water – Supply & Use
Groundwater
– Vadose zone (formerly known as the unsaturated zone)
– Zone of saturation or water table– Capillary fringe
– In general, water moves through the subsurface as a function of:
• Permeability – ability of a material to transmit fluid
• Porosity – percentage of void space in a material
• Be careful not to confuse these two terms!
Show flash animation: http://geomorph.geology.ufl.edu/~adamsp/Outgoing/Lectures2030/Animations/WaterTable.html
Aquifers
“zone of earth material capable of supplying groundwater at a useful rate from a well.”
Can be composed of gravel, sand, soil, fractured rock with sufficient pore space (sandstone, granite, metamorphics)
Example of Unconfined Aquifer
Aquifers
Confined Aquifer
Aquiclude or Aquitard forms a confining layer, due to much lower permeability – can hold water, but not transmit it fast enough to support well pumping.
Zone of Recharge – where precip. infiltrates the surface to enter the groundwater system (eventually, the aquifer)
Recharge can be natural or artificial.
Artesian conditions – pressurized water that emerges from surface to a level of the pressure surface.
Groundwater Pumping
Show flash animation: http://geomorph.geology.ufl.edu/~adamsp/Outgoing/Lectures2030/Animations/ConeDepress.html
Causes “discharge”, as opposed to recharge
Forms a cone of depression
Groundwater Movement
Hydraulic gradient – approx. the slope of the water table
Hydraulic conductivity – ability of a material to allow water to move through it – expressed as a velocity (m/day)
Porosity and Permeability
Groundwater Movement
D'Arcy's Law (black board example next lecture)Q = KIA
Q=discharge (Q)K= hydraulic conductivityI= hydraulic gradientA= cross-sectional area (confined aquifer)More complicated when unconfined because
h= thickness varies)
Henry Darcy
More Groundwater
Potentiometric Surface and Hydraulic Head
Driving force for groundwater movement is hydraulic head, usually the elevation of the potentiometric surface
Groundwater always moves from an area of higher head to one of lower head (i.e., from high potentiometric contours to lower contours)
Interaction of Groundwater and Surface Water
Influent streams (Losing)
Effluent streams (Gaining)
Springs