Water

The World’s Water  Approx. 97% of the Earth’s water is salt water  Approx. 3% is fresh water. – Of this 3%, most is frozen in the ice caps and in glaciers – This leaves only about ½% of all Earth’s water as usable fresh water  Most of this usable fresh water is found underground  All of the Earth’s water is part of the hydrosphere

Water Cycle  Movement of water from one part of the hydrosphere to another is called the water cycle  The energy to start the water cycle comes from the sun (causes evaporation to begin)  Water enters the air as vapor from evaporation and transpiration (water given off by plants)  The vapor forms clouds, precipitation occurs, and the water flows back into the ground or into other bodies of water  The cycle then begins again – this is a continuous cycle

Where does rain go?  Evaporates before it hits the ground.  Run off ---if ground is impermeable or slope is steep  Infiltrate – moves into the ground ( if ground is porous and permeable)

Water in the Ground characteristics

 POROSITY The percentage of open space in the soil  (The amount of water that the ground can hold depends on the amount of open space (pore space) between the soil particles)

The porosity of the soil depends on:  Particle shape – Rounded particles do not fit together well, so they will have more space between them – Angular pieces fit together (like a puzzle), and therefore will have less space between them Rounded fragments Angular Fragments

The porosity of the soil depends on: Sorting Sorting  Well-sorted particles (all the same size), don’t fit together well and have the greatest pore space  Unsorted particles have small particles which fit between large particles, decreasing the amount of open space

Packing  Particles that compacted together will have less open space between them.

**Particle size does not affect the porosity** Large particles have large spaces, but few of them. Small particles have small spaces, but many of them. The porosities will be equal!!

Permeability the ability of a liquid to pass through a material’s pore space

 Usually permeability will increase as the size of the particles increases  The larger the particles, the larger the pore spaces  Liquids (water) move easier through larger openings – (water moves easier through a fire hose than through a garden hose)

gravel sandclay

Impermeability  If a liquid cannot pass through a material, then it is considered to be impermeable  If a material is porous but the pores are not connected, then the material will be impermeable

Soil Water Movement

 When water infiltrates (soaks) into soil, it gets pulled through the pores by gravity  The water continues to flow downward until it reaches an impermeable layer  The water then begins to fill in the pore spaces above the impermeable layer – (like filling a glass with soda – the soda hits the bottom of the glass and then begins to fill the glass)

 zone of saturation The layer of soil where all of the pore spaces are filled is called the  water table – top of saturated zone  zone of aeration (air fills the pore spaces) above the water table  capillary fringe – This is where tiny droplets of water move upward by attaching to small particles of soil

Capillarity  Ability of water to move upward  Capillarity is greatest when pore spaces are small.

The Water Table

 The depth of the water table varies, depending upon the amount of rainfall, seasons, climate, soil thickness, etc.  Where the water table does not reach the surface, a pipe may be drilled into the ground down to the water table.  Water may then be pumped out (similar to using a straw to drink with) through the pipe. – This is called an ordinary well. – If the water flows out of the pipe without being pumped, because of the pressure in the ground, it is called an artesian well.

Groundwater below a layer of solid rock or clay is in a confined aquifer. The rock or clay is called a confining layer. A well that goes through a confining layer is known as an artesian well.

 Groundwater usually remains cool all year. Because of its depth, groundwater is not affected by the weather changes at the surface  Below 20 meters deep, water may become heated by the Earth’s interior.  If it becomes heated to boiling, hot springs may rise to the surface.  They may also erupt as gushing springs of boiling water and steam called geysers – (Yellowstone National Park in Wyoming is famous for its hot springs and geysers)

 Groundwater can dissolve limestone underground.  Carbonic acid naturally found in groundwater dissolves the calcite in limestone.  Eventually, large portions of the limestone are dissolved and a cavern (cave) may form. – Howe Caverns in upstate New York is an example of a limestone cavern.

Groundwater Contamination Groundwater can become polluted by many different means

Sinkholes

Devil’s Sinkhole, Rocksprings, Texas