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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