SAS' Ecology Page

Sweet Fresh Water (Focus on water cycle)

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Freshwater

1. Accounts for 3% of the total volume of water on Earth.
2. Freshwater comes from rain, precipitation

Water cycle

1. Precipitation
1. Starts as rain
2. Runoff
1. Rain flows over land, forming streams
2. Streams merge, becoming rivers
1. rivers carry more water than streams
3. If river's path run into a basin (a hole in the ground), and it forms a lake
1. Lakes acts to isolate species
1. few fish, plants or invertebrates move beyond the lakes.
4. Rivers have several stages,
1. River stages based upon size, water velocity, and amount of particles in the water.
2. Stage 1
1. Fast moving water,
2. abundant rapids
3. Not a large river,
4. fairly fresh, with little or no particles (e.g. mud) in the water
3. Stage 2
1. Several rivers merge,
2. rapids become stronger,
3. water's force increases.
1. moving house-size boulders,
2. cutting deep gorges into the river bank.
4. Stage 3
1. River banks widen,
2. River slows,
3. waters rich in nutrients
5. Stage 4
1. River slows to a sluggish pace
2. Mud settles,
1. forming curves in the river.
2. river path changes often.
3. Plant life dramatically increases
6. Stage 5 (last stage)
1. River spreads over a acres of land
1. marshes, mangroves and swamps forms
2. River merge with the ocean
1. tides flush marshes with saltwater and freshwater periodically
2. Water salinity brackish (less than 33%_o).