II. Section 2 Water on the Surface

A. River Systems 1.Tributaries- the smaller streams and rivers that feed into a main river 1.Watersheds- the land area that supplies water to a river system 2.Divides- what separates one water shed from another 3.Continental Divide- longest divide in North America, follows Rocky Mountains

B. Rivers and Floods 1.Flood- volume of water in a river increases so much that the river overflows it’s channel 2.As speed of a river increases so does its energy 3.Flooding river- uproot trees, wash away houses and bridges 4.Egypt- people welcomed the flooding of the Nile for fertile soil 5.In history floods have killed millions of people

C. Can Floods Be Controlled? 1.Dam- a barrier across a river that may redirect the flow of the river to other channels or store water in an artificial lake 2.Can open a dam’s gate during dry season to release stored water 3.During floods water can rush through and break or over the dam 4.Levees- long ridges alongside the channel 5.Can make matters worse downstream of a flood- surge of water

D. Bodies of Freshwater 1.Ponds usually smaller and shallower than lakes 2.Sunlight usually reaches the bottom of a pond where in a lake parts are too deep 3.Ponds and lakes form when water collect in hollow and low-lying areas of land

E. Ponds 1.Plants grow throughout the pond because sunlight can reach the bottom of the pond 2.Though photosynthesis these organisms create oxygen 3.Some ponds only appear in the Spring then evaporate in Summer 4.Some may freeze during winter

F. Lakes 1.The bottom is usually filled with mud and algae 2.Lake formation a.Cutoff river meander b.Ice age depressions c.Deep valleys formed by movement in the crust d.Volcanic craters e.Man made- reservoir- a lake that stores water for human use 3.Plants do not live at the bottom of lakes 4.Home of large boney fish

G. Changes in a Lake 1.Undergo changes with season 2.Cool water becomes more dense with the change of the season and mixes with the warmer water 3.This change is called lake turnover- refreshed the supply of nutrients throughout the lake 4.Eutrophication- nutrients in a lake build up- algae grows and builds up on the surface 5.This happens because organisms are constantly releasing waste products

G. Changes in a Lake 6. When the layer becomes so thick it blocks sunlight- no photosynthesis 7. Organisms die and oxygen decreases 8. Lakes bottom becomes completely filled with plants and a grassy meadow takes the place of the lake

H. Icebergs 1.Glacier- a mass of ice and snow that moves slowly over land 2.When a glacier reaches a seacoast an iceberg forms 3.Although they are in the ocean they are made up of freshwater 4.Only 10% of an iceberg is visible the rest is under water 5.International Ice Patrol tracks icebergs-created after Titanic