Earth: The water planet

Earth: The Water Planet

WATER IS EVERYWHERE

1 in 8 people lack access to clean freshwater!

Where is our water?

People and water

• Many areas with high population density, do not have a lot of water.

• Other areas have plenty of water, but fewer people.

• These situations cause inequalities in per capita water resources.

Seasonal Availability

-Fresh water is distributed unevenly in time as well as space.

-Many parts of the world experience distinct rainy and dry seasons.

-Because its distributed unevenly, its hard to move fresh water from its source to where its needed.

Water is either

​SURFACE WATER

​GROUNDWATER

Surface water

Surface water is contained within watersheds

• 1% of freshwater is surface water (water found on the surface).

• Examples are rainfall, melting snow, glaciers, ice caps.

• Runoff: water that flows over land and has not been absorbed into the ground.

• Runoff can flow into lakes or ponds or join up with a river system.

River Systems

​-Water moves downhill because of gravity, forming a network of connected streams and rivers called a river system.

Watersheds

​Watersheds includes all of the land area that supplies water to a particular river systems.

​Watersheds sometimes are called drainage basins b/c they drain into a river system.

Groundwater

​Groundwater can be accessed by wells

​water found below Earth's surface.

makes up 1/5 of Earth's water supply and plays a key role in meeting human water needs.

​permeable- layers containing spaces or pores so water can pass through.

​impermeable- layers with few or no pores so water can't get through easily.

Aquifers are sponge like formations of rock, sand and gravel that hold water.

​Water table is a boundary between the two zones.

​Recharge zone- any area where surface water soaks into the ground and goes to aquifer below.

​Well- a hole dug into an aquifer to reach groundwater

​-wells are dug deep into saturation zone, so they will not dry up during seasonal droughts.

​-If the water table drops below the well's depth, the well will run dry. You must dig deeper.

​OGALLALA AQUIFER