Draw a meander and label these locations: erosion, deposition, faster water, and slower water.

Warm – Up 2/6

GroundwaterSprings, Wells, and Aquifers

Movement and Storage of Groundwater

97% contained in the oceans 3% of this water contained by landmasses

(nearly all freshwater) More than 90% of freshwater on Earth in

the form of polar ice caps and glaciers Remaining freshwater is groundwater Rivers, streams, lakes only small portion of

Earth’s freshwater

The Hydrosphere: water on and in Earth’s crust

Evaporation of ocean waters, forms clouds/precipitation, weather systems and winds move this moisture build up all over Earth

Falls to land and enters ground through infiltration, becoming groundwater (solid precip. stays for longer periods of time until melting)

Groundwater moves through ground, returns to surface via springs, then flows back to oceans.

Precipitation and Groundwater

Subsurface materials contain pores; the amount of pore space in material called porosity

The greater the porosity, the easier water can flow through subsurface materials

Large quantity of groundwater are stored in the pore spaces of rocks and sediments

Groundwater Storage: Where does the water go?

Def: depth below Earth’s surface at which groundwater completely fills all the pores of a material

Upper boundary of this zone= water table Only the water in the zone of saturation

is called groundwater Above the water table, materials are moist,

but because they are not saturated with water, air occupies much of the pores. This area is called the zone of aeration.

The Zones

Depth varies with local conditions In stream valleys groundwater is close

to the surface; water table only few meters deep

Hilltops/arid regions tens to hundreds meters deep

Water table fluctuates with season and weather conditions because of its dependence on precipitation

The Water Table

Flows downhill in direction of slope of the water table

Moves extremely slow because the water has to travel through numerous tiny pores

Ability of material to let water pass= permeability Large connected pores= high permeability

(sand and gravel) Silt and clay=tiny pores=impermeable Steeper slope of water table= higher velocity

of groundwater

Groundwater Movement

Most groundwater flows through permeable layers known as aquifers

In aquifers, the pore spaces are large and connected.

Aquicludes: barriers to groundwater flow; these layers are impermeable because the pores of materials are small.

Aquifers

The exact places where groundwater emerges depend on the arrangement of aquifers and aquicludes in an area.

Where aquifers and aquiludes come in contact, groundwater will discharge at Earth’s surface. This area is called a spring.

Springs

Groundwater Erosion and Deposition

Dissolution and formation of calcium carbonate play role in formation of limestone caves

Cave: natural underground opening with connection to Earth’s surface

Formed when groundwater dissolves limestone

Most develop in the zone of saturation just below water table

Dissolution By Groundwater

Sinkhole: depression in the ground caused by the collapse of a cave or by the direct dissolution of bedrock by acidic rain or moist soil

Disappearing Streams: feature that occurs when a surface stream drains into a cave system and continues flowing underground, leaving a dry valley above.

Limestone regions that have sinkholes and disappearing streams are said to have karst topography

Karst Topography

Hard Water: contains high concentration of calcium, magnesium, or iron

Common in limestone areas Deposits of calcium bicarbonate can clog

water pipes

Groundwater Deposits

The most remarkable feature produce by groundwater are the rock formations called dripstones. They decorate many caves above the water table.

The formations are built over time as water drips through the cave.

Each drop of water hanging on the ceiling of a cave loses carbon dioxide and precipitates calcite (calcium ion)

Groundwater Deposits

Stalactites: hangs from the cave’s ceiling like icicles and forms gradually as minerals buildup from precipitated groundwater.

Stalagmites: found on the cave’s floor as a mound-shape; they are made over time by water dripping to the floor.

Types of Dripstone

Wells: holes dug or drilled into the ground to reach an aquifer.

Wells: Ordinary and Artesian

The simplest wells are those that are dug or drilled below the water table, into what is called a water-table aquifer.

How it works: as water is drawn out of a well, it is replaced by surrounding water in the aquifer.

Overpumping of the well lowers the water level and creates a depression around it.

Drawdown: the difference between the original water level and the new water level after pumping.

Recharge: water from precipitation replenishes the water content of an aquifer.

Ordinary Well

An aquifer’s area of recharge is often at a higher elevation the rest of the aquifer.

An aquifer that contains water under pressure is called an artesian aquifer. This pressure is due to the aquifer being located between aquicludes.

When the rate of recharge is high enough, the pressurized water can spurt above the land surface creating a fountain known as an artesian well.

Artesian Well