Watersheds and Stream Order

Watershed Watershed: The land drained by a river or stream and all of its tributaries. Also known as a Drainage Basin. Watershed boundaries, or divides, are typically defined by the highest elevation that drains a stream.

Watersheds The rate at which water travels through a watershed is determined by factors such as: its size (total surface area) topography (flat or steep) amount and type of vegetation human development The total amount of water that collects in a river that drains the watershed is called its Discharge. Discharge is measured in meters3/second. Total Discharge

Drainage Patterns Drainage patterns depend mostly on: (1) topography; and (2)the type of rock over which streams flow.

Stream Order Stream Order: a system of classifying streams and rivers based on their relationship or position in the drainage network. Streams at the beginning of the system are called first-order streams. First order streams receive water directly from a source such as a spring, lake, melting snow, etc. When two first order streams join, the resulting stream is now classified as a second-order stream.

Stream Order Note: the stream order will increase only when two like streams join.

Slide 1: Stream Order Identify the proper stream order for each of the following locations. 1 3 2 4

Slide #2 Lackawanna River Watershed Name the mountains that act as the boundary/divide on the eastern portion of the Lackawanna River watershed. How many counties comprise the Lackawanna River watershed? The Lackawanna River eventually flows into which larger river? Which type of drainage pattern is dominant in the Lackawanna River watershed?

Slide 3: Stream Gradient 1 2 3 Place in order from fastest stream velocity to slowest the three locations in the above diagram. Which number would best illustrate a youthful stream? Which number would best illustrate a mature stream? Which number would carry the largest sediments (pebbles, cobbles, boulders)? Which location is most likely to have extensive meandering? Small sediments like sand and silt will be most likely found at which location?

Slide 4: Mississippi Watershed Name the mountains that cause the divide on the western boundary of the watershed. 2. Name the mountains on the eastern boundary

Slide 5: PA’s Major Watersheds 1. Name the bodies of water that each watershed eventually drains into. 2. Which watershed includes the Lackawanna River watershed?

Drainage Patterns Slide #6 #B Slide #6 Identify the type of drainage pattern for each example and; Discuss how, geologically, each pattern forms. #C #D

Watershed Questions 1. Describe the relationship between stream order and the size of a watershed. 2. Describe how humans can affect a watershed. Give specific examples. 3. Describe how increased human development will affect how surface water travels through a watershed. 4. Compare a saturated and unsaturated geosphere and how each will influence the rate of surface water flow and discharge of a watershed.

Watershed Dynamics All of the following watersheds are equal in surface area and receive equal rainfall. Compare and contrast each of the following watersheds: Discuss specifically, a. the rate of surface water flow through each watersheds (faster or slower) b. possible disruptions to flow. Give specifics! c. final discharge (more or less) 5. Flat (slope) terrain vs. steep (slope) terrain 6. Agricultural vs. forested land 7. Rural development vs. urban development