Transcript II. Section 2 Water on the Surface

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.
b.
c.
d.
e.
Cutoff river meander
Ice age depressions
Deep valleys formed by movement in the crust
Volcanic craters
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