groundwater Flashcards
aquifer
underground geological formations that hold and transmit water
aquitard / aquilude / confining layer
rock or sediment that is non permeable, cannot transmit water, block groundwater flow
water table
boundary line between saturated and unsaturated zones, equal pressure to the atmosphere
saturated zone
area in the sediment where its pores are filled with water
unsaturated zones
area in the sediment where the pores are filled with mainly air and water vapor
capillary fringe
small area of saturation above water table, sucked up by capillary forces
unconfined aquifer
open to infiltration, no confining layers above
confined aquifers
closed by an aquitard, water underneath is under high pressure, so when opened up to surface it can naturally flow all the way up
perched aquifer
above the water table, perched on a confining layer
porosity
proportion of empty space in a substance, expressed as percent
specific yield
the amount of water that drains out of an unconfined aquifer under gravity if the water table were to lower expressed as a percent
specific retention
the opposite of specific yield, the amount of water that is not pulled out by gravity, stays due to molecular attraction with sediment
transmission
an aquifers ability to allow water to flow away and into it or an aquitards ability to block the flow of water, dependent on hydraulic conductivity and permeability
permeability
a substances ability to allow any form of liquid pass though, dependent on the sediment
hydraulic conductivity
a substances ability to allow a specific liquid to pass through, dependent on the sediment and the liquid
molecular attraction
attraction between molecules due to poles, water is polar because of the way its electrons are oriented giving it a negative and positive side
viscosity
viscosity is a measure of thickness in a liquid
density
mass per unit of volume
viscosity and density relation to groundwater flow
more viscous liquids will have slower groundwater flow, if temperature increases the density decreases because its molecule get farther apart, this in turn decreases viscosity and increases groundwater flow
fractures
cracks in low porosity sediment, allow for high permeability by giving the water cracks to flow through, also allows for pollution because of the faster flow rate due to larger more interconnected cracks
what drives groundwater flow
pressure and gravity, gravity pulls the water down and pressure causes the water to move from low pressure to high pressure
why does groundwater not go above the water table?
its reached the equilibrium of pressure and doesn’t need to go up anymore
how does pumping water from well affect groundwater flow?
it sucks water up towards the well, causing groundwater to flow towards the well instead of natural places like streams and lakes and oceans
cone of depression
a funnel shape in the water table made by wells, because the well is sucking water up it decreases pressure and lowers the water table in that area
compressibility
how much a confined aquifer can change in shape, more compressibility results in more water storage and more water extraction
interconnectivity
how connected the pores in a substance are
turtuosity
how straight of a path there is in a sediment
recharge
refilling of an aquifer, usually from rain
infiltration
water moving into a sediment, water on the surface infiltrates into the sediment
percolation
after infiltration, the actual movement of water through the sediment
what areas tend to have higher and lower pressure?
valleys have lower pressure because there is less sediment stacked up
hills and mountains have higher pressure because there is more sediment stacked up
what is packing and how does it affect permeability, porosity, and retention?
packing is how compressed together the sediment particles are
as packing increases, permeability and porosity decrease and retention increases
what is angularity/sediment shape and how does it affect permeability, porosity, and retention?
angularity is how cornered or rounded the sediment particles are
as angularity increases, permeability and porosity decreases and retention increases
what is sorting and how does it affect permeability, porosity, and retention?
sorting is how well sorted the particles are in a sediment. low sorting means that different sediments types and sizes are mixed together
as sorting increases, permeability and porosity increase and retention decreases
what is the vadose zone?
same as the unsaturated zone
what are some things that affect the porosity of an aquifer?
sorting: how sorted sediment is, bad sorting results in smaller particles filling pores, decreasing porosity
cementation: minerals dissolved in water act as a glue connecting sediment particles together
overburden stress: pressure caused by weight of rocks and fluids, increases packing and therefore decreases porosity
grain shape: more angular sediments have lower porosity
physical weathering: cracks and disintegration, creates fractures and widens them
chemical weathering: decomposition, increases size of cracks and pores
