14.1 Water in the 14.1 Water in the GroundGround

Key Idea: Key Idea: Factors such as the porosity and Factors such as the porosity and

permeability of soil and rock materials permeability of soil and rock materials affect the storage and movement of affect the storage and movement of

water in the ground.water in the ground.

GroundwaterGroundwater The natural conditions of a region The natural conditions of a region

determine the direction where the water determine the direction where the water from precipitations goes. For example:from precipitations goes. For example:

-in the mountains, much of the water will -in the mountains, much of the water will flow on the slopes as run-off, and will be flow on the slopes as run-off, and will be collected by streams and rivers.collected by streams and rivers.

- in the desert the water will evaporate - in the desert the water will evaporate quickly.quickly.

-in areas with loose soil and rocks that are -in areas with loose soil and rocks that are permeable, much of the water will seep permeable, much of the water will seep into the ground, and stored as into the ground, and stored as groundwater. groundwater.

GroundwaterGroundwater

Properties of Rocks that Allow Properties of Rocks that Allow Groundwater to Accumulate. Groundwater to Accumulate.

1. Porosity1. PorosityGround water accumulates in rocks that Ground water accumulates in rocks that

allow the water to seep through. The rocks allow the water to seep through. The rocks must have cracks, or spaces in between must have cracks, or spaces in between particles; these spaces are commonly particles; these spaces are commonly called pores. The property of having pores called pores. The property of having pores is called porosity.is called porosity.

2. Permeability 2. Permeability The pores must be connected together in The pores must be connected together in

order to let the water seep through. The order to let the water seep through. The rate at which water passes through the rate at which water passes through the pores of rocks is called permeability. pores of rocks is called permeability.

Porosity Porosity

Porosity depends upon a number of Porosity depends upon a number of factors, such as:factors, such as:

- - particles’ shapeparticles’ shape: materials : materials consisting of rounded particles have consisting of rounded particles have more porosity than the materials more porosity than the materials having angular particles.having angular particles.

- - sorting: sorting: the amount of pore space the amount of pore space is is greater in materials that have is is greater in materials that have particles of the same size. particles of the same size.

Example of PorosityExample of Porosity

Various Types of PorosityVarious Types of Porosity

2. Permeability2. Permeability

Permeability differs greatly among rocks:Permeability differs greatly among rocks: Loose rocks such as gravel and sand have food Loose rocks such as gravel and sand have food

permeability. permeability. Larger grains will have larger pore spaces. Larger grains will have larger pore spaces. The finer the grains of the rock, the less porosity The finer the grains of the rock, the less porosity

and permeability the rock has.and permeability the rock has. Some rocks have pores but the pores are not Some rocks have pores but the pores are not

connected at all. Pumice is an example of such a connected at all. Pumice is an example of such a rock.rock.

Limestone is not a porous rock, but it is has many Limestone is not a porous rock, but it is has many cracks that make this rock permeable. cracks that make this rock permeable.

AquifersAquifers

The water that seeps into the ground will The water that seeps into the ground will be collected in porous rocks, such as sand be collected in porous rocks, such as sand and gravel; this water will form an aquifer.and gravel; this water will form an aquifer.

At the base of all aquifers there is a layer At the base of all aquifers there is a layer of impermeable rocks. of impermeable rocks.

Sometimes there are alternating layers of Sometimes there are alternating layers of permeable and impermeable rocks, that permeable and impermeable rocks, that might favor the formation of more than might favor the formation of more than one aquifer (like in the above picture).one aquifer (like in the above picture).

AquifersAquifers

The Water Table The Water Table

An aquifer is an accumulation of An aquifer is an accumulation of underground water. underground water.

The area where water fills the aquifer The area where water fills the aquifer is called the is called the saturated zone saturated zone (or (or saturation zone). The top of this zone saturation zone). The top of this zone is called the is called the water tablewater table. The water . The water table may be located only a foot table may be located only a foot below the ground’s surface or it can below the ground’s surface or it can sit hundreds of feet down. sit hundreds of feet down.

The Water TableThe Water Table

Factors Affecting The Water TableFactors Affecting The Water Table

The water table can be at the surface of the The water table can be at the surface of the ground, such as in swamps and some ground, such as in swamps and some lakes; its depth depends on many factors:lakes; its depth depends on many factors:

Amount of rainfallAmount of rainfall Amount of time that passes between rainsAmount of time that passes between rains SeasonSeason The slope of the groundThe slope of the ground Thickness of the soilThickness of the soil Climate type. Climate type.

Factors Affecting The Water TableFactors Affecting The Water Table

In humid climates the water table is close In humid climates the water table is close to the surface.to the surface.

In desert regions the water table may be In desert regions the water table may be hundreds of yards below the surface.hundreds of yards below the surface.

In the woods it is likely to be closer to the In the woods it is likely to be closer to the surface, where the tree roots can reach it. surface, where the tree roots can reach it.

In hilly country it is closer to the surface in In hilly country it is closer to the surface in the valleys.the valleys.

Wells Wells

Wells provide drinkable water to many Wells provide drinkable water to many people that have no access to other people that have no access to other sources of water. sources of water.

People who live in the desert have to People who live in the desert have to dig very deep wells to get the water dig very deep wells to get the water table. table.

Many rural communities all over the Many rural communities all over the world rely mainly on ground water. world rely mainly on ground water.

A Well DiagramA Well Diagram

Contamination of GroundwaterContamination of Groundwater

SpringsSprings

On a hillside where the groundwater On a hillside where the groundwater meets the surface, groundwater may meets the surface, groundwater may flow out as a spring. flow out as a spring.

Afka Afka SpringSpring

in in LebanonLebanon

Artesian SpringsArtesian Springs

Sometimes the aquifers form in hilly areas. Sometimes the aquifers form in hilly areas. If the aquifer is trapped in between two If the aquifer is trapped in between two impermeable layers of rocks and it is impermeable layers of rocks and it is charged at the top by precipitations, then charged at the top by precipitations, then the water table might be way above the the water table might be way above the ground level at the base of the hill. ground level at the base of the hill.

If a well is dug at the base of the hill, then If a well is dug at the base of the hill, then the water might spout upward with the water might spout upward with pressure, rising several feet, or yards pressure, rising several feet, or yards above the ground level. This is an artesian above the ground level. This is an artesian well. well.

Artesian WellArtesian Well

Artesian WellArtesian Well

Hot Springs, Geysers, and Hot Springs, Geysers, and FumarolesFumaroles

Hot springs, geysers and fumaroles Hot springs, geysers and fumaroles are manifestations that are related to are manifestations that are related to magma- tic activity.magma- tic activity.

Hot springs Hot springs If the ground water travels nearby a If the ground water travels nearby a

mass of hot magma, the water can mass of hot magma, the water can easily reach boiling point, and its easily reach boiling point, and its pressure increases. The water comes pressure increases. The water comes out the ground as a hot spring. out the ground as a hot spring.

GeysersGeysers

A geyser is an intermittent hot A geyser is an intermittent hot spring. It shoots hot water and steam spring. It shoots hot water and steam into the air at certain intervals of into the air at certain intervals of time: weeks, days, or hours. time: weeks, days, or hours.

In Yellowstone Park there is one In Yellowstone Park there is one geyser named Old Faithful which geyser named Old Faithful which erupts every 89 minutes. erupts every 89 minutes.

Old FaithfulOld Faithful

FumarolesFumaroles

In areas with recent volcanic activity, In areas with recent volcanic activity, where magma is still very hot, the where magma is still very hot, the groundwater is heated to the boiling groundwater is heated to the boiling point, and reaches the surface at hot point, and reaches the surface at hot steam. steam.

These columns of hot steam are These columns of hot steam are called fumaroles. (The Latin work called fumaroles. (The Latin work “fumus” means steam) “fumus” means steam)

Fumaroles at Yellowstone National Fumaroles at Yellowstone National ParkPark