Hydrosphere p. 298-301

Hydrosphere Formed by all bodies of water on the Earth’s surface Includes oceans, rivers, streams, lakes and other waterways

Hydrosphere Covers 75% of Earth’s surface Without water there would be no life Water can either be fresh or salty

Why are the seas and Oceans salty? Seas and Oceans are salty because there are a great quantity of mineral salts dissolved in it Mineral salts come from rocks When it rains, some minerals (which form the rocks) dissolve Minerals run into the ocean where they accumulate

Are some Seas saltier than others? The amount of salt in seas vary depending on the region in the world The Dead Sea – Saltwater Lake in the Middle East with salinity of 27%

Which type of water can humans drink? Humans can only drink fresh water because they can’t absorb the large quantity of mineral salts contained in salt water When water is safe to drink it is called potable. Potable water = drinkable water

Potable Water To be potable water it must have the following characteristics: Perfectly transparent No suspended particles No unpleasant odour Contains little dissolved minerals Contains dissolved oxygen No micro-organisms that cause disease

Potable Water 7 billion people in the world (March 2012) 780 million people in the world without access to adequate water and sanitation 3.5 million people die each year from water, sanitation, and hygiene-related causes. The rate of child deaths is equivalent to a jumbo jet crashing every four hours. Water is whose responsibility?

But how much water is available for humans to drink? Works out to be about 0.02% available fresh water

The Water Cycle Where this is the way earth cleans its water – but there is a limit

The Water Cycle a) Evaporation - water from lakes, rivers and oceans changes to water vapour by the action of the sun. b) Transpiration - water vapour is released from plants by the action of the sun. c) Condensation - water vapour changes to droplets of liquid as it cools, leading to the formation of clouds.

d) Precipitation - water from clouds is released back into lakes, rivers and oceans, as rain, snow or hail, or onto land where it seeps through the soil and travels as ground water back to the ocean. e) Melting - ice and snow change to liquid water by the addition of heat, and flow into lakes, rivers and oceans. http://camillasenior3.homestead.com/watersystems2.html

People upset the natural water cycle That is because we: Create pollution Remove the natural vegetation such as plants and trees Pave over the natural environment and build houses etc. Put in irrigation systems, build dams, change natural drainage systems, build wells