Presentation on theme: "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."— Presentation transcript:
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
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)
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 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