EA_LandscapebyWater_SubmissionTemplate_Summer2023_rev1
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Feb 20, 2024
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Florida SouthWestern College
Intro to Earth Sciences
Running Water: Landscapes Fashioned by Water
Directions: Complete the answers using the Pearson Intro to Earth Science textbook and/or any indicated web resources. Although you can work together as a group, each individual student should compose their own well-conceived and articulate answers. Please submit the .docx AnswerTemplate to the Atmosphere Composition, Structure, and Temperature assignment page
.
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Objectives
Identify and explain the processes acting on the Earth’s surface that create and shape landforms (CO6)
List the hydrosphere’s major reservoirs and characterize the different paths that water takes through the hydrologic cycle. (MLO 1)
Characterize the nature of drainage basins and river systems. (MLO 2)
Describe streamflow characteristics and the factors that cause them to change. (MLO 3)
Summarize the ways in which streams erode, transport, and deposit sediment. (MLO 4)
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Part 1. The Hydrologic Cycle - Textbook Ch 9.1
1.
List the reservoirs where Earth’s water is held. Include the percentages of Earth’s water for each reservoir. Make sure to read all the way to the end of Ch 9.1
Oceans house most of the Earths water supply at about 96.5%. The Earths fresh water supply stored in groundwater, lakes, rivers and ice accounts for about 2.5%, and the last 1% is in saline lakes and saline groundwater. Of the 2.5% freshwater about 68.6% of it is stored in Glaciers and Ice sheets, 30.1% is stored
as non-saline Groundwater, and 1.3% is Surface water and other sources. Of the
1.3% Surface water it includes Swamps (2.53%), Soil moisture (3.52%), Rivers (0.46%), Biological (0.22%), and Atmosphere (0.22%).
Florida SouthWestern College
Intro to Earth Sciences
The three major movements of water on Earth are 1) evaporation, 2) precipitation, and 3) runoff 2.
Over the ocean, which pathway of water dominates? The Hydrologic Cycle is a balanced system. Over the Ocean Evaporation is the dominant pathway. The Ocean evaporates approximately 320,000km3 annually to balance the 284,000km3 of precipitation over the ocean and 36,000km3 of runoff due to precipitation over land.
3.
Over land, there are several possible pathways that water may follow? List them
and decide which one dominates? Over land after precipitation water can either infiltrate the ground, become runoff heading downhill towards lakes, rivers, streams or the Ocean, or evaporate back into the atmosphere. Evaporation is the dominate pathway accounting for 60,000km3 of the annual 96,000km3 of precipitation.
Part 2. Drainage Basins and Systems – Textbook Ch 9.2
4.
Define the major components of a drainage system (drainage basin, drainage divide, tributary)
A Drainage Basin as an area of land that basically catches rainwater and directs it toward a main trunk stream. A Drainage Divide is the outer ridge or crest of the basin and separates one basin from the next. If a drop of water falls to the left of the divide it goes into the left basin and vice versa. A tributary is the waters mode of transportation such as rills or gullies down to the main trunk stream.
5.
How do most streams grow in length?
Florida SouthWestern College
Intro to Earth Sciences
Most streams grow in length through Headward erosion. As water is drained off the divide it erodes away the starting points of the tributaries and stretches them further uphill toward the divide. Eventually they can break through the divide and join another basin strengthening one and weakening or killing the other.
6.
How much of the continental US does the Mississippi R. drain? What type of drainage basin system does it have?
The Mississippi river drainage basin drains over 40% percent of the runoff for the continental United States. This is a massive Dendritic pattern drainage basin made up of 6 Sub-Basins. Part 3. Streamflow Characteristics – Textbook Ch 9.3
7.
What are zones A and C called?
Zone A is called The Zone of Sediment Production (erosion). Zone C is called the Zone of Deposition.
8.
Which part of the river region shown above (A, B, or C) has the greatest gradient or slope? Why is this the case?
Zone A has the greatest gradient. This area is the Headwaters and is located furthest up the slope of the Drainage Divide.
9.
Which part of the river region shown above (A, B, or C) has the greatest stream discharge. Why is this the case?
Zone C has the greatest amount of discharge because as you move down the stream, from the headwaters to the mouth of the stream, it is fed by more and more tributaries. So, by the time you meet the mouth of the stream it has the largest amount of water to discharge possible.
10.
Describe what the bottom roughness and the channel size of the river in region A would look like. Find and paste a web-based image of a river that has
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Florida SouthWestern College
Intro to Earth Sciences
these characteristics, noting the name of the river and where this river section might be located. (Read section 9.5 for help)
Zone A would have a very rough channel bottom and the channel size would be quite small.
Below is a picture of a tributary in the Deerfield River located in Heartwellville VT.
Part 4. Erosion, Transport, and Deposition of Sediment – Read Textbook Ch 9.5-7 and Watch the video (link below)
After reading the text and watching the short film using satellite imagery about changes in
the landscape of the Ucayali River from 1985-2013: Ucayali River Flipbook
, answer questions 11-13.
11.
What would the textbook call the tan/brown regions on the corners of each bend of the Ucayali R? Does erosion or deposition dominate these locations.
Florida SouthWestern College
Intro to Earth Sciences
The textbook refers to this region as a point bar. Deposition dominates in this area because water moves slower on the inside of a stream bend cause floating sediment to fall out of suspension and collect there.
12.
In 1995, a flood inundated the Ucayali R. and two banks of the river joined together. What would the textbook call these types of riverbanks? Are they on the outside or the inside of the river? Would erosion or deposition dominate this bank type?
The text refers to this type of bank as a cutoff. A cutoff happens on the outside banks of two sections of a meandering river as erosion eats the banks away until they join together and cut off a part of the river forming an oxbow lake.
13.
Would you expect laminar or turbulent flow in the river during the flood of 1995. Explain your answer.
I would expect turbulent flow in the river during a flood because as rivers increase in water volume there is less friction to slow the waters down.