science chap 9 Flashcards
Distribution of Water on Earth
Less than 3 % of all water on Earth is freshwater
Most freshwater is frozen
Less than 1% of all water on Earth is accessible for use by organisms
Aquifer
underground permeable layer of rock that stores water.
Water Table:
uppermost level of water in the aquifer.
Artesian Well:
a hole is dug into a confined aquifer. The pressure allows water to flow up and out of the well.
How is a cone of depression formed?
When the water table lowers after heavy pumping
Saltwater Intrusion
Rapid pumping of wells drilled in aquifers along a coastline can lower the water table.
Lowering the water table reduces water pressure in the
aquifer, allowing the nearby salt water to move into the aquifer and contaminate the well water with salt.
Human Activities can make Droughts Worse
Conversion of grasslands to crop land increases soil erosion by wind and water when there is a drought. Drought can cause crop failure and more erosion. When crops die and are removed, plant roots can no longer hold soil in place.
Early 1930’s a severe drought in several states caused crop failure and the
Dust Bowl.
April 14, 1935 is known as Black Sunday because the Sun was blocked by dust.
This led to a decade of dust storms in the US.
Impervious / impermeable cover
is any surface in the landscape that cannot absorb or infiltrate rainfall. This includes driveways, roads, parking lots, rooftops, and sidewalks. This leads to increased runoff and flooding when storm drains and sewers cannot keep up with heavy rainfall.
Levee
an enlarged bank built up on each side of a river.
Dike -
Structure built to prevent ocean waters from flooding adjacent land.
Levees are good
- prevent flooding of floodplain land where crops can grow and people can live.
Levees are bad…
- encourages building on flood plains where flooding can still occur.
- causes flooding and increased sediment deposit downstream.
Dam -
A barrier that runs across a river or stream to control the flow of water, and creates a reservoir of water.
Dams hold water for human consumption, generation of electricity (hydroelectric power), flood control.
Fish Ladders
help migrating fish get around the dam.
Aqueduct -
a canal, ditch, or pipe used to carry water from one location to another.
Desalination -
the process that removes salt from salt water.
Reverse Osmosis
s less expensive but salty brine is left behind and needs to be disposed of.
Worldwide water is used for agriculture more than anything else
hi
Flood:
entire field is flooded. Can be disruptive to plants. 70%-80% efficient
Furrow:
easy, inexpensive. Farmer digs trenches or furrows along rows of crops and fills them with water.
65% of water accessible to plants
Spray:
water is pumped from a well and sprayed across the field. 75%-95% efficient, but more expensive.
Drip:
Most efficient method of irrigation. Uses slowly dripping hose laid on the ground or buried beneath soil.
Hydroponic Agriculture
The growth and cultivation of plants in a greenhouse by immersing roots in a nutrient-rich solution.
Expensive BUT:
- Requires little or no use of pesticides.
- Uses up to 95% less water than traditional irrigation.
- Crops can be grown year round.
