Categorize+stream+order+in+a+watershed.


 * Explain the concept of stream order. **

The Strahler stream order measures the size of rivers. The twelfth-order is the largest stream, the Amazon River. The smallest are the first-order streams. First-order streams have water year-round (perennial streams). They have no permanent tributaries. Second-order stream are when two first-order streams join together. When two second-order streams join, a third-order stream forms. If a first-order stream and a second-order stream join with each other, it is still a first-order stream (Kreger 2004).



The start of a watercourse is a rill on a slope resulting from rain, snow, or other sources of water. The start of a river is called its headwaters, When it flows down the hill, numerous rills join together and form a brook. When brooks join together, a stream is formed. As the stream widens, it becomes a creek. If it continues downhill and gets even larger, it becomes a river. Branches of the river are called tributaries. They add water to the river. A river and all of its tributaries is a water basin. Watersheds are all the areas that drain to a certain river. Another source of the water in rivers is from underground. The end of a river is called the mouth ("River" 2005).
 * Identify the order of watercourses within a major rivers watershed. **

The place where a stream starts is called the headwater. It usually is located in the mountains. The headwater is the upper course of the river. In the upper course, the river is small and rapid with a strong flow that can roll huge rocks. In the upper course, there are waterfalls that carry large pieces of stones and gravel. After many years, the water curves away a V-shaped valley ("River" 2005). The water is cold, clear, and low in nutrients. The stream is narrow with fast water running through it. Photosynthetic organisms like algae live here. Other animals include insects and fish that get food with their sight (Campbell and Reece, 2001).
 * Compare and contrast the physical differences found in the stream continuum from headwater to mouth. **

As the river flows down, the water's force is smaller and does not have the strength to carry large sediments. This part of the river is called the middle course. The large sediments are deposited at the riverbed where bars are formed, and they continue to grow as more things are dropped. These structures can shape the course of the water. The V-shaped valleys are weathered into U-shaped valleys ("River" 2005). The stream or river widens and slows down. Wetlands and ponds are usually located downstream. The water is warm and murkier due to the sediments and phytoplankton floating in it. Organisms that live here include worms, insects, birds, frogs, and fishes that get food with scent.

As the water further flows downward, the flow gets gentler and this part of the river is the lower course. This part of the river, more sediments are deposited and they build up on the riverbed. In this part of the river, the river is in a S-shape and tends to meander. The valley is now a plain. When flooding occurs, the narrow parts of the river sometimes break off and form a new channel. This new channel is called an oxbow lake. When water levels go down, bars of sediments appear and the original river that meandered is now braiding. The end of the lower course, which is the end of the river, is called the mouth. The mouth is where the river meets the sea. In this part of the river, all of the sediments are deposited and a delta is formed. A delta is a triangular-area formed when sediments build up ("What is a Stream?" 1998).

Home