Groundwater
Groundwater is water that completely fills (saturates) the
pore spaces of soil or rock formation below the water
table. Water that shares pore space with air is called soil
moisture.
Groundwater is the largest reservoir of fresh water that is
readily available to humans
Four factors that influence the rate at which water enters the
groundwater “system”
1. Type of rock or soil
2. Climate (in dry areas, a lot of water evaporates before it soaks into the ground.)
3. Topography (steep slopes = runoff)
4. Vegetation (more vegetation = more water stays where it lands)
PorosityPorosity is percentage of total volume of rock
or sediment that consists of pore spaces.
Porosity
Factors that affect porosity
Particle shape (round sediments have more pore spaces than angular sediments)
Sorting (poorly sorted sediments have fewer spaces than well-sorted sediments, because smaller pieces fill the spaces between bigger ones)
Permeability
Permeability is the ability of water to flow through a rock or sediment layer, or the rate at which it does so.
Factors that affect permeability
Pore Size- larger the pore space are, the easier water passes through. Clay and silt-sized sediments can be impermeable, because their shape allows them to overlap one another like stacks of paper.
Interconnection of Pores- Pumice is not permeable because, although it is very porous, its holes are not interconnected.
Presence of cracks in rock layers
Water Table
What Factors affect the Water table?
Amount of Rainfall-more rain = higher water table
Amount of time between rains
Season
Slope
Soil thickness
Climate
How much water is being removed
Aquifer
An Aquifer is an underground layer of water-bearing, permeable rock, or unconsolidated sediment, from which groundwater can be easily extracted.
Aquifer
Gravitational pressure
Perched Aquifers (Springs)
Artesian Well
Geyser
Groundwater Contamination
Saltwater Intrusion
Falling water table
Karst TopographyKarst is a topography in which the landscape is largely shaped by the dissolving action of acidic water on carbonate bedrock (usually limestone, dolomite, or marble).
This geological process, occurring over many thousands of years, results in unusual surface and subsurface features ranging from sinkholes, vertical shafts, disappearing and emerging streams, and springs, to complex underground drainage systems and caves.
Karst provides water for many Virginians.
Vertical Shafts
Underground Rivers
Caves
Sinkholes
Karst Counties in Virginia
West- Virginia Karst
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