Rivers are nearly everywhere in the
United States. We often see them while crossing bridges and we know
that there is moving water there, but where is all that water coming
from and where is it going? Rivers are formed by a watershed. A
watershed is an area of land where rainwater flows into valleys
forming streams. These streams flow into other steams and eventually
form a main stream or river. Some rivers form from an overflow of a
lake like the mighty Mississippi River that begins at Lake Itasca,
Where does all that water go?
As the illustration at left shows, the rain
falls and collects in the valley, then the water usually flows on to
other rivers and eventually to the sea. After the water reaches the
sea, some of it evaporates and forms clouds. These clouds drift over
the land and release rain back into the watershed. This is the cycle
of water. Some may ask, "What happens if it doesn't rain for a
long time?" That is a good question because we will still see
water flowing in the river, even during droughts. The answer is
groundwater. When the river level gets low the water that is in the
ground seeps into the riverbed and helps to keep the river flowing,
even though it will be much lower than normal.
What is a divide?
A divide is high ground or mountains
that cause the beginning of streams to flow in different directions. The direction of a river flow is
powered by gravity. Let's look at the Rocky Mountain Range. All the
rain fall and snow melt on the easterly side of the mountains will
flow downhill toward the east and the rainfall and snow melt on the
westerly side of the mountain will flow downhill toward the west. The
peak of these mountains is the divide between river systems. This
mountain range is called the Continental Divide but there are smaller
divides throughout the country where streams form. Shown is a divide
in western Ohio that is only about six feet higher ground than the
three rivers that form there. The beginning of a river is called the
How far does a river go?
Most rivers are a connection to the
rest of the world! Not only rivers but even the tiny steams that flow
into the rivers are part of a huge watery route that leads to many
far away places. If we placed a rubber duck in a tiny stream, where will it go? I will float down the stream with the current and go into a larger stream or a river. The rubber duck will continue it's journey down the river to a larger river and eventually to an ocean. Once in the ocean, the rubber duck could end up landing at a coastline anywhere in the world, depending on the ocean currents and wind. It would be possible that if the rubber duck was placed in a tiny stream in Illinois, it could land on the coast of the continent of Africa.
Why do rivers meander?
Meandering is the constant loops or
bends in a river as opposed to flowing in a straight line. It would
seem that the force of gravity would cause the river to run straight
but there are other factors involved in a flowing river besides
gravity. Sometimes a bend forms in the river because the land becomes
more resistant to the flow, like rock. This sends the river into a
different direction. There is also a natural vibration to water flow
that will cause banks to erode and form new bends. Watch water flow
down a car windshield. It will not usually flow straight, but in
wiggles. River bends are also created when the scouring action of the
water erodes a riverbank. The soil then gets deposited on the
opposite side and builds up on the inside of the new band. This
causes even more current (speed and direction of the water) to be
pushed to the outside of the bend and it continues to grow into a
How are rivers named?
Most American rivers were given names
by the Native Americans with some being corrupted over the years to
something different. One example is the Wabash River. It was
originally called Wa-Bah-Shika, then the French Explorers called it
Ouabache. River names originated from a local area so the names often
do not reflect the true source and mouth of a river. The source is
the beginning and the mouth is the end of a river. River distances
are measured by the names they were given and not necessarily by
their actual length. Following is an example of an interesting
concept about river lengths.
It is widely accepted that the Missouri
River is the 15th longest river in the world. In the natural order of
things it is actually the 3rd longest river in the world. The
Missouri River headwaters (actual beginning of the river) is located
in the Rocky Mountains and is called Hellroaring Creek. This Creek
then becomes the Red Rock River. The Red Rock River flows into a
large reservoir (lake with a dam). As the water flows over the
reservoir dam it becomes Beaver Creek. When Beaver Creek joins the
Big Hole River, the waterway becomes the Jefferson River. When the
Jefferson is joined by the Madison and Gallatin Rivers it becomes the Missouri
River. The Missouri River then flows for 2,341 miles to where it
becomes the Mississippi River. It then flows another 1,106 miles to
the Gulf of Mexico. If we visualize a drop of water falling into
Hellroaring Creek and follow it, the drop would travel a total
distance of 3,902 miles before ending up in the ocean. If this
waterway had only one name from beginning to end it would then be the
3rd longest river in the world. The map below shows the river length from the mountains to the sea.
Who owns the rivers?
We all own the rivers! In the United
States most rivers are for public use and are not privately owned.
The land along the rivers and even some islands may be private owned.
Some smaller streams may be considered property of the landowner.
Most states have lists of the waterways that are designated as
public. In most cases the river shoreline is also for public use up
to the high water mark. The high water mark is normally at a point
where trees and grasses grow that cannot survive being submerged for
long periods of time. This means during normal and low water, there
is usually adequate land to access along the river. In some cases
there are controversies between states with regard to water rights of
a river, particularly when the river serves as a border between
states. These tug-of-war issues must usually be settled in the
Why are rivers important?
In addition to the water cycle
mentioned earlier, rivers provide for a huge variety of wildlife and
fish. Another important aspect of rivers is transportation. Rivers
are like a watery highway and have been since Native Americans canoed
great distances. It was much easier to travel and carry burdens on a
river than to do so across the thick forests. We still use rivers for
transportation from pleasure boats to commercial vessels. The United
States has over 25,000 miles of navigable rivers. Navigable means
that the river has a deep enough channel to operate commercial boats
like tugboats and large cruisers. The 3.5 million miles of rivers in
the United States play an important role in our commerce, recreation
What is the difference between a river
and a creek?
Rivers are generally regarded as being
larger than a creek but there is no other difference with regard to
their place in the water cycle, their meandering or their journey to
the sea. Rivers are simply large creeks. There are many names for
creeks that are given for various reasons. Those include brooks,
streams, rivulets, runs, rills, licks and branches.
Why do rivers flood?
Rivers have always flooded. It is a
natural part of the river system. Rivers have floodplains.
Floodplains are large areas of land along the rivers that flood
during high water. The flood plains serve several purposes. The river
replenishes the land with nutrients, helping plant life and crops
grow. They also serve as release valves along the river bank to allow excess water to go where it will do no harm. Flood Plains also create
wetlands for our wildlife. Over the years many of these flood plains
have been cut-off with levees. Levees are large mounds of earth built
along the shore to stop the river from flooding low lying areas. At right is a cut-away side view of a levee. Even
though levees are designed to prevent flooding they actually create
flooding in other areas.
When levees are built, the natural
flood plains are cut off and the excess water must go somewhere. The
water will rise higher where the levee is built, then flood other
areas that do not have high river banks. These areas may have not
flooded before the levees were built but do now because of levees
built elsewhere. We will never stop flooding on our rivers because
that is what rivers do. What human intervention has done is to cause
flooding to occur more often and at higher levels in places that did
not used to flood, like our cities. It is ironic that the very
structures that were built to prevent flooding actually play a part
in causing them. This lesson has been learned on the lower
Mississippi River where they have built spillways. Spillways are
large gates that they can open to allow the floodwaters to flow into
floodplains once again.
Are our rivers polluted?
Yes and No! Some of our rivers,
particularly those flowing from mountains are quite clean. Other
rivers have various concentrations of chemicals as a result of
agricultural run-off (farm fields) and industry. Very often we see
the brown waters of a river and may think that it is dirty but that
is not always the case. Many rivers are alluvial. Alluvial means that
they naturally carry sand and silt (soil). This is a natural process
that creates a delta at the river's mouth. A delta is land that is
formed by this material piling up at the end of a river, extending
into the sea. Deltas provide great wetlands for wildlife. The good
news is that our rivers are showing less content of pollutants each
year. This is due to the efforts of government legislation (new
laws), better farming practices to reduce run-off and many great
organizations that have formed to clean up and prevent pollution.
Are rivers safe to wade or swim?
Some rivers have beaches or designated
swimming areas that are safe when adults are present. Most rivers
have characteristics that make them unsafe for swimming. The current
in a river is usually stronger than it looks and a swimmer can be
swept downstream. There is also debris (floating objects) in rivers
that can be hazardous for swimmers. NEVER wade in a river. The
current flows over submerged objects like sunken logs, creating a
backwash on the downriver side of the object. The backwash digs a
hole with steep sides. These holes are very dangerous. A riverbed can
drop off to a very deep level very quickly, catching a wader off
guard. Again..Never wade in a river!
Why are dams built in rivers?
There are several reasons why rivers
are dammed and very often a combination of reasons. Following are
four types of dams and what they do:
1. Lowhead Dams..This is the most
common type of dam. They are designed to hold some water back in
order to have deeper water above the dam. There is no control over
how much water flows past the dam, since it spills over the top of
the dam. Many of these dams were built in the days when mills
operated on the rivers. The water passed through the dam in a flume
(opening) and turned a large waterwheel that was connected to a
grinding mill for making flour and other items from grain. They are also
called grist mills. The illustration at right shows how the power of
water is transferred to the grinding wheel.
2. Navigational Dams...These dams were
built to keep deep water above each dam so that the channel (deepest
part of the river) is suitable for commercial boats. They have locks
that allow boats to pass through the change in water levels from
above and below the dam. Locks on the river are like watery stairways
and boats must be raised or lowered to the next level, depending on
whether they are going upriver or downriver. Upriver boats will be
raised and boats going downriver will be lowered. Shown at right is a
vessel locking downriver. Notice that no pumps are used. Gravity fills
and empties the lock chamber.
3. Hydroelectric Dams...These are
usually higher dams that take advantage of the power created by water
falling from above the dam to below the dam. Large turbines are
installed in the path of the water. Turbines have fins inside of a
tube that cause it to spin as the water passes through. This powers a
generator that creates electricity. This method is much cleaner than
coal-fired power plants. See the video below for more information about how hydroelectric plants work.
4. Flood Control Dams...Rivers often
run through large valleys that can be several miles wide. When a dam
is built the valley will fill with water. This is called a reservoir.
The dam has control gates so that the amount of water passing through
can be adjusted. This control allows the operators to keep the
reservoir low in anticipation of rainy season or snow melt. When the
river normally would flood, this valley will have enough capacity to
hold the additional water and prevent downstream flooding. The dams
are also used for holding water in reserve, so that during very low
water some of it can be released downstream when it is needed.
Another benefit to reservoirs is that they provide recreation
opportunities like boating, swimming and fishing.The photo at right
shows the natural river, then how it looked after a dam was built and
the valley filled with water.
dams like the Kentucky Dam on the Tennessee River perform several
functions including navigation, electricity, flood
control, recreation, drinking water and wildlife habitat. Other dams
have out lived their purpose and been abandoned. When this happens
they cause the river to become stagnant. Stagnation is when the river
is no longer flowing as it should and silt builds up above the dam.
There are organizations currently addressing this with a goal of
removing some of the dams to allow the river to become free-flowing
once again. Rivers have an amazing power of self-healing. Once a dam is
removed or the point of pollution stops, the river will eventually clean
itself and become restored to its original natural beauty.
What are some historic American river
There is no doubt the Lewis & Clark
Expedition was the greatest river journey in history. Beginning in
Pittsburgh, PA the Corp of Discover (their unofficial name) went down
the Ohio River, then up the Mississippi River, then up the Missouri
River to the headwaters. They then portaged the Rocky Mountains and
found their way to the Snake River and Columbia River, then made it
to the Pacific Ocean. Their discoveries, maps and journals changed
In 1869 Civil War veteran Major John
Wesley Powell and his men went over 1,000 miles down the treacherous
Colorado River. They discovered many unknown aspects of the river and
mapped it for future travelers. Their journey through the Grand
Canyon provided much new information about this National Landmark.
Powell later became director of the United States Geographic Survey.
Robert La Salle was a French explorer
who traveled the Great Lakes to the Mississippi River and became the
first European to explore the Mississippi River all the way to the
Gulf of Mexico in 1682. Even though his mission was to establish
fur-trade routes along the river and he claimed the Mississippi River
for France, his explorations opened the door to a greater
understanding of the river for future travelers of the waterway that
would eventually become part of the United States.
We should embrace our rivers for their
beauty and value, while protecting them for future generations. There
are many river and watershed organizations taking part in cleanups
and activism that helps to protect our rivers against pollution and
exploitation. Get to know your local watershed and join us in our
efforts to create public awareness of these valuable resources; our
rivers. After reading this and discovering even more about our
rivers, you will see the river differently while crossing a bridge.
You will understand what it is like "Beyond the Bridges".