FRESHWATER CORNELL NOTESR. Michelle EsserweinPalmer Middle School6th Grade AC Science

Distribution of WaterEarth stands out from other planets in our

solar system primarily for one reason----WATER!!!

71% of Earth’s surface is covered with water97% Salt Water3% Freshwater

Ice Shallow groundwater Deep groundwater Lakes/Rivers Water Vapor

GroundwaterWater located within the rocks below Earth’s surface.

Important resourcePlays an important role in erosion & deposition.

Underground Layers

Location of GroundwaterSurface water seeps underground

into the soil & rock.Underground area divided into two

zones:Zone of aerationZone of saturation

Two zones meet at a boundary known as the water table.

Zone of AerationThe area above the

water table is the zone of aeration.

This permeable layer allows the water to infiltrate down to the water table.

Also called “unsaturated zone”.

Zone of SaturationWhen water reaches

an impermeable layer, it cannot soak in any deeper.

The spaces between the rock particles are filled with water.

If you dig a hole this deep you will see your hole start to fill with water.

Saturated means to soak or fill completely.

Water TableThe top of the saturated

zone is called the water table.

The more it rains, the higher the water table will get.

The more water you take out through a well, the lower the water table will get.

Knowing the depth of the water table will tell you how far down you must dig to find water.

Where the water table is above ground you will find streams, ponds, and lakes.

AquifersA body of rock or

sediment that stores groundwater and allows the flow of groundwater.

Usually form in permeable materials: sandstone, limestone, layers of sand/gravel.

Some cover large, underground areas.

Important water source for cities and agriculture

PorosityPercentage of the total volume of a rock

or sediment that consists of open spaces.More open spaces/pores = more water it

can hold (i.e. an aquifer)Influenced by differences in sizes of

particles in the rock layer.Layer w/many particles of different sizes

= low porosity as small particles will fill up empty spaces.

Layer w/many same-sized particles=high porosity as there is more open space between the particles.

PermeabilityAbility of a rock or

sediment to let fluids pass through its open spaces or pores.

The larger the particles, the more permeable rock layer.

Sand and gravel will have large pores between the grains, so they are very permeable.

ImpermeableDoes not allow water to easily pass

through.Has few pores or cracks.Will cause water to pool on top of it.Clay and granite are impermeable.

Recharge ZoneAquifers need a constant supply

of water to maintain the water table via the water cycle.

The ground surface where water enters an aquifer is called the recharge zone.

Size depends on how permeable the rock is at the surface.

Aquifer covered by an impermeable rock layer, water cannot reach it.

Construction of buildings on top of the recharge zone also limits the amount of water that enters an aquifer.

Bringing Groundwater to the Surface

SpringsIf the water table is at ground level, water may flow out of the ground.

This is called a spring.Usually occur on sides of hills or in low areas.Important source of drinking water.

Artesian SpringsArtesian formation: Sloping layer of

permeable rock sandwiched between two layers of impermeable rock.

Permeable rock = aquiferTop layer of impermeable rock = cap rockArtesian spring: Spring whose water flows

from a crack in the cap rock of the aquifer.Often found in deserts.

WellsA human made hole that extends down past the water table.

Water must be pulled or pumped up to be used.

Dries up when water table falls below the bottom of the well.

Underground Erosion & DepositionGroundwater causes erosion by dissolving rock.Contains weak acids (carbonic acid); dissolves rockTypes of rock (limestone) dissolves in groundwater

easily.Underground erosion forms caves.Caves are also a sign of deposition.Water drips from a crack in the cave’s ceiling leaving

deposits of calcium carbonate.Stalactites=Sharp, icicle-shaped features; form on

cave ceilings.Stalagmites=Cone-shaped features; form on the

floor of a cave from water falling from above.Dripstone column=Stalactites and stalagmites form

together.

Underground Erosion & Deposition (continued)When the water table is lower than

the level of a cave, the case is no longer supported by the water underneath.

Roof of cave collapses, leaving a circular depression called a “sinkhole”.

Often form lakes in areas where the water table is high.

Example: Central Florida is covered with hundreds of round sinkhole lakes.

Sinkhole in Winter Park, Florida