Groundwater Flashcards
On Exam 2 (Apr 1)
Where is our freshwater supply?
Mainly kept in ice/glaciers
Most of our accessible fresh water is in the ground, then in surface water (lakes, rivers, etc.)
What is porosity?
The volume of empty space in a rock (relative to the volume of sediment particles)
In other words, are there cracks or pore spaces?
What is permeability?
How well a fluid flows through a network of pores and cracks in the rock
In other words, are the pores spaces connected to one another?
What factors influence porosity and permeability?
Sorting: if they’re well sorted, there are more pores
Grain size: larger grains mean more cracks
Rounding: more rounded means more cracks
What is the water table? What is below it? Above it? What affects it?
The boundary between the Zone of Saturation (below) and the Zone of Aeration (above)
The water table will change based on the seasons, storms, floods, droughts, etc.
Recharge vs Discharge
Re = replenishment of groundwater (downward movement of rain)
Dis = removal of groundwater (upward movement via springs or wells)
What is an aquifer? Aquitard? Aquiclude?
FER = rock that easily transports and stores water (porous and permeable)
TARD = rock that allows for transport and storage, but not as easily as an aquifer
CLUDE (think EXCLUDE) = rock that does not allow the transport or storage of water (not porous or permeable, probably fine-grained)
Unconfined vs Confined Aquifer
Unconfined - water can move freely
Confined - there is a boundary or impermeable layer of rock (like an aquiclude) preventing the water from leaving the aquifer
What is an Artesian Well? How does it work?
A well that brings water to the surface without pumping
This is due to natural differences in pressure: when you drill a well or dig a hole, you are removing sediment and decreasing the pressure in that area, so water will naturally move from the area of high pressure (the sediment) to the low pressure (the hole)
How does groundwater connect to plate tectonics?
Where there are igneous intrusions (common near plate boundaries where rock is melting or magma is rising), groundwater can be heated, causing it to rise and form various features (geysers, fumaroles, hot springs)
Hot Spring vs Fumarole vs Geyser
H.S. = heated water sitting in a pool
Fumarole (think FUMES) = steam vent
Geyser = cyclic, explosive emissions of water
How are normal springs (not hot springs) formed?
1 - recharge (rainfall collects)
2 - chemical weathering from acidic water = cracks
3 - more weathering = widening of cracks into caves
4 - groundwater flows into caves
5 - further weathering makes the ground unstable = collapse of cave into a sinkhole
6 - hole = pressure differences = groundwater flows towards it
What features are associated with springs?
Caves and sinkholes
The presence of limestone (which dissolves in acid)
What are human uses of springs?
Drinking water, irrigation and agriculture, industrial and domestic use
How does human overuse of groundwater affect the water table?
Leads to a Cone of Depression (holes in the ground near wells that eventually collapse) and Surface Subsidence (the downward settling of rocks as water is replaced with air)
What are some other ways that humans affect groundwater?
Use of groundwater may lead to Saltwater Intrusion, which is nearly impossible to remove
Contamination from agriculture, livestock, landfills, sewage, industrial waste, etc.
How does climate change affect springs and groundwater?
More droughts and less snow = less water for recharge = surface subsidence
Bottled water - good or bad?
Requires mass amounts of water and energy to create
Generates lots of plastic waste
However, it can be useful for emergency situations
