:max_bytes(150000):strip_icc():format(webp)/200435538-001-58b9cec75f9b58af5ca81efd.jpg)
........................................................................................
Watersheds
Overview of Watersheds and Watershed
Management
by Amanda
Briney
A
watershed, also called a "drainage basin" in North America, is an
area in which all water flowing into it goes to a common outlet, such as the
same estuary or reservoir.
Watersheds
themselves consist of all surface water and include lakes, streams, reservoirs,
and wetlands, as well
as all groundwater and aquifers.
The
water in a watershed originates via precipitation that
is collected on the surface and groundwater.
However,
it is important to note that not all precipitation falling in an area exits the
watershed. Some of it is lost through evaporation and
transpiration, some is used by people and some soaks into the soil and
groundwater.
At
the boundaries of watersheds, there are drainage divides usually in the form of
ridges or hills. Here the water flows into two separate watersheds and does not
always end up in a common outlet.
In
the United States, for example, there are many different watersheds, but the
largest is the Mississippi River basin which drains water from the Midwest into the Gulf of Mexico.
This water does not enter the Pacific Ocean because the Rocky Mountains act as
the drainage divide.
The
Mississippi River basin is an example of an extremely large watershed, but
watersheds vary in size.
Some
of the world's largest ones contain smaller watersheds within them depending on
where the final water outlet is.
Types of Watersheds
The
second is called a major drainage divide. In this situation, waters on each
side of the boundaries do not meet via the same river or stream, but they do
reach the same ocean.
For
example, there is a drainage divide between the Yellow River (Huang He) basin
and the Yangtze River in China but both have the same outlet.
The
final type of drainage divide is called a minor drainage divide. In these,
waters separate at the divide but later rejoin. An example of this situation is
shown with the Mississippi and Missouri Rivers.
Key Features of a Watershed
The
second feature is the drainage divide or watershed boundary, such as a mountain
range. This plays a role because it helps in determining whether the water in
the watershed is flowing toward or away from an area.
The
next feature is the topography or terrain of the watershed's land. If the area
is steep, the water there is likely to flow quickly and cause flooding and
erosion, whereas flat watersheds have often had slower flowing rivers.
The
final feature of a watershed's physical landscape is its soil type. Sandy
soils, for example, absorb water quickly, while hard, clay soils are less
permeable. Both of these have implications for runoff, erosion, and
groundwater.
Significance of Watersheds
By
studying the key watershed features in addition to activities along waterways
scientists, other researchers and city governments can work to keep them
healthy because a small change in one portion of a watershed can drastically
affect other parts.
Human Impacts on Watersheds
Watershed
pollution occurs in two ways: point source and nonpoint source.
Point
source pollution is pollution that can be traced to a specific point such as a
disposal site or leaking pipe. Recently, laws and technological advances have
made it possible to detect point source pollution and its problems are being
reduced.
Nonpoint
source pollution occurs when pollutants are found in water running off of
crops, parking lots and other lands. In addition, it can also be caused when
particulates in the atmosphere fall onto the land with precipitation.
Humans
have also impacted watersheds by reducing the amount of water flowing within
them.
As
people take water out of a river for irrigation and other city-wide uses, the
river's flow decreases and with this decreased flow, natural river cycles such
as flooding, may not occur. This could, in turn, hurt ecosystems depending on
the river's natural cycles.
Watershed Management and Restoration
Watershed
restoration, on the other hand, is aimed at restoring already impacted
watersheds to their natural state through the monitoring of pollution and
regulations to reduce further pollution.
Watershed
restoration programs also work often to repopulate the watershed with its
native plant and animal species.
Amanda Briney
· Professional geographer, writer, and scholar
· More than 10 years of experience writing about a broad array of
geographical topics
· Holds three university degrees and an advanced certificate in
GIS
Experience
Amanda Briney is a professional geographer and
writer who contributed to ThoughtCo for more than 10 years. She wrote countless
articles on a wide range of topics such as an introduction to the subject of
geography, reviews of ecotourism, discussions about environmental determinism,
and the structure of Latin American cities. The scope of her work also includes
other formats such as histories, guides, and fact sheets about many parts of
the world. An ultimate scholar, Amanda also contributes work to academic venues
and the GIS Lounge, an informational portal about geography.
Amanda enjoys all aspects of
geography and mapping but is especially interested in examining natural
landscapes through spatial analysis. As such, she holds a certificate in
Geographic Information Systems (GIS) from California State University. She also
attended Diablo Valley College where she studied air photo interpretation and
the formation of the Earth's landscapes.
Education
Amanda Briney received a
Master Arts (M.A.) in Geography from California State University–East Bay. She
also holds a Bachelor Arts (B.A.) in English and Geography from California
State University–Sacramento and a earned a Certificate of Advanced Study in
Geographic Information Systems (GIS) from California State University.
ThoughtCo
and Dotdash
ThoughtCo is a premier reference site focusing on
expert-created education content. We are one of the top-10 information sites in
the world as rated by comScore, a leading Internet measurement company. Every
month, more than 13 million readers seek answers to their questions on
ThoughtCo.
For more than 20 years, Dotdash brands
have been helping people find answers, solve problems, and get inspired. We are
one of the top-20 largest content publishers on the Internet according to
comScore, and reach more than 30% of the U.S. population monthly. Our brands
collectively have won more than 20 industry awards in the last year alone, and
recently Dotdash was named Publisher of the Year by Digiday, a leading industry
publication.
