Bell Activity #24
Read each sentence and decide if it is a fact, reasoned
judgment based on research, or speculation.
1) According to a 1998 U.S. Geological Survey report,
water use in the United States has decreased 2% since
1990 and almost 10% since 1980, despite an increase in
population. 2)The report attributes this to public
awareness and conservation efforts. 3)People probably
spend less time in the shower these days, compared to
how much time they spent in the shower in 1980.
Objectives
• Describe how moving water shapes the surface of the
Earth by the process of erosion.
•
Explain how water moves through the water cycle.
•
Describe a watershed.
•
Explain three factors that affect the rate of stream
erosion.
•
Identify four ways that rivers are described.
I. Rivers: Agents of Erosion
A. What Is Erosion? Erosion is the process
by which soil and sediment are
transported from one location to another.
II. The Water
Cycle
A. The Movement
of Water The
water cycle is
the continuous
movement of
Earth’s water
from the ocean
to the
atmosphere to
the land and
back to the
ocean.
III. River Systems
A. Water Network A river
system is a network of
streams and rivers that
drains an area of its runoff.
A tributary is a stream that
flows into a lake or larger
stream.
B. Watersheds River systems
are divided into regions
called watersheds. A
watershed, or drainage
basin, is the area of land
that is drained by a water
system.
IV. Stream Erosion
A. Gradient Gradient is the measure of the
change in elevation over a certain
distance. A high gradient gives a stream
or river more erosive energy to erode
rock and soil.
B. Discharge The amount of water that a
stream or river carries in a given amount
of time is called discharge.
C. Load The materials carried by a stream
are called the stream’s load. The size of
a stream’s load is affected by the
stream’s speed.
V. The Stages of a River
A. Youthful Rivers A youthful river erodes its
channel deeper rather than wider.
B. Mature Rivers A mature river erodes its
channel wider rather than deeper.
C. Old Rivers An old river has a low gradient
and little erosive energy.
D. Rejuvenated Rivers Rejuvenated rivers
are found where the land is raised by
tectonic activity.
Critical Thinking Time
• How does the water cycle help develop river
systems?