Chesapeake Bay
Why Study the Bay?
The Chesapeake Bay is the largest estuary in the country and is vitally important to the ecology and economy of Virginia. Approximately half of the state's watersheds flow into the Bay. Thus, a large percentage of the state affects the health of the estuary. All but a small section of the Coastal Plain of Virginia touches the Bay and relies on it for transport, import/export, water, recreation, and industry. I have chosen to discuss the topics of river systems and pollution in this section because of their relevance to any discussion of the Chesapeake Bay. Watersheds
A watershed is any area drained by a particular river system. Watersheds can be broad in area (the Gulf of Mexico watershed or Mississippi River watershed) or more narrow in focus (the Dan River Basin). In Virginia, there are four major watersheds making up the Chesapeake Bay watershed: James River, York River, Rappahannock River, and Potomac River. |
Estuaries
An estuary forms when salt water and fresh water mix as rivers meet the ocean. Estuarine waters are sometimes called brackish to describe the mixture of salt and fresh water. Estuaries are also tidally influenced, so that the amount of salt water increases or decreases with the ebb and flow of tides. Estuaries can form four different ways: drowned river valley; bar-built lagoon, glacial fjord; tectonic subsidence. The Chesapeake Bay is an example of a drowned river valley and formed when sea levels rose to flood large coastal river valleys.
An estuary forms when salt water and fresh water mix as rivers meet the ocean. Estuarine waters are sometimes called brackish to describe the mixture of salt and fresh water. Estuaries are also tidally influenced, so that the amount of salt water increases or decreases with the ebb and flow of tides. Estuaries can form four different ways: drowned river valley; bar-built lagoon, glacial fjord; tectonic subsidence. The Chesapeake Bay is an example of a drowned river valley and formed when sea levels rose to flood large coastal river valleys.
The other types form as follows:
Glacial fjord: a glacier carves its way toward the ocean, forming deep, narrow valleys that fill in when sea levels rise. Bar-Built lagoon: sandbars form along the coast and inhibit the flow of seawater on either side of the sandbars forming a brackish lagoon. Tectonic subsidence: during continental divergence, the land stretches and falls down along normal faults; seawater floods these sunken blocks when the boundary breaches the coastal barriers. |
River Systems
The word "river" refers to a relatively large body of moving water. A river gets bigger as smaller rivers, creeks, and streams give over their waters to the larger river. These smaller bodies of water are, thus, called tributaries as they are giving a "tribute" of their water to the larger body. Essentially, all rivers are tributaries in their own right as they give their water over to an even larger body of water, such as a lake or an ocean.
Rivers also grow old in definite stages: Young or Youthful, Mature, and Old-Age.
The word "river" refers to a relatively large body of moving water. A river gets bigger as smaller rivers, creeks, and streams give over their waters to the larger river. These smaller bodies of water are, thus, called tributaries as they are giving a "tribute" of their water to the larger body. Essentially, all rivers are tributaries in their own right as they give their water over to an even larger body of water, such as a lake or an ocean.
Rivers also grow old in definite stages: Young or Youthful, Mature, and Old-Age.
Young
Young rivers have fast flowing water through a narrow, V-shaped valley with no floodplain. Mature Mature rivers still have swift water, but the valley has flattened a little on the bottom to create a U-shaped valley; there is also a slight floodplain Old-Age Old rivers are slow, meandering rivers in a flat bottom with a wide floodplain; the meanders consist of cut banks on the outside of bends and point bars on the inside of bends; when the river cuts across a bend, an oxbow lake is formed. |
Pollution
There are two major types of pollution: point source and non-point source. These terms refer to where the pollution comes from as well as our ability to remediate the situation. Point source pollution usually comes from a single or easily identifiable source and can therefore be stopped or remediated. Non-point source pollution comes from an unidentifiable source or too many sources to be effectively remediated. A leaking sewer pipe is an example of point-source pollution while exhaust from cars, trucks, planes, boats, etc. is an example of non-point source pollution.
There is another way of classifying pollution based on the type of pollutant: toxic, nutrient, sediment, or bacterial. Toxic pollution consists of industrial chemicals and heavy metals. Sediment pollution occurs when large amounts of sediment cloud streams and rivers. Bacterial pollution comes from animal waste among other sources. Nutrient pollution sounds almost counterintuitive. How can nutrients pollute? One way is through a process called eutrophication.
Eutrophication is of utmost importance to places like the Chesapeake Bay and Gulf of Mexico. As excess fertilizer washes off of cropland, it flows into bodies of surface water where it encourages algae growth. Algal blooms block sunlight from marine plants, causing them to die. The amount of algae is too great to be completely consumed by fish and it, too, begins to die off. Dying organisms decompose which pulls oxygen out of the water. The water turns hypoxic (low oxygen content), but more algae bloom due to the fertilizer's nutrients. Hypoxic conditions lead to anoxic (no oxygen) as more things die and decompose either from not being eaten or from suffocating. Eutrophication leads to "dead zones."
There are two major types of pollution: point source and non-point source. These terms refer to where the pollution comes from as well as our ability to remediate the situation. Point source pollution usually comes from a single or easily identifiable source and can therefore be stopped or remediated. Non-point source pollution comes from an unidentifiable source or too many sources to be effectively remediated. A leaking sewer pipe is an example of point-source pollution while exhaust from cars, trucks, planes, boats, etc. is an example of non-point source pollution.
There is another way of classifying pollution based on the type of pollutant: toxic, nutrient, sediment, or bacterial. Toxic pollution consists of industrial chemicals and heavy metals. Sediment pollution occurs when large amounts of sediment cloud streams and rivers. Bacterial pollution comes from animal waste among other sources. Nutrient pollution sounds almost counterintuitive. How can nutrients pollute? One way is through a process called eutrophication.
Eutrophication is of utmost importance to places like the Chesapeake Bay and Gulf of Mexico. As excess fertilizer washes off of cropland, it flows into bodies of surface water where it encourages algae growth. Algal blooms block sunlight from marine plants, causing them to die. The amount of algae is too great to be completely consumed by fish and it, too, begins to die off. Dying organisms decompose which pulls oxygen out of the water. The water turns hypoxic (low oxygen content), but more algae bloom due to the fertilizer's nutrients. Hypoxic conditions lead to anoxic (no oxygen) as more things die and decompose either from not being eaten or from suffocating. Eutrophication leads to "dead zones."