Stream morphology

ENVIRONMENTAL SCIENCE

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STREAM MORPHOLOGY

Overview Students will construct a physical scale model of a stream system to help understand how streams and rivers shape the solid earth (i.e., the landscape). Students will perform several experiments to determine streamflow properties under different conditions. They will apply the scientific method, testing their own scenarios regarding human impacts to river systems.

Outcomes • Design a stream table model to analyze the different

characteristics of streamflow. • Explain the effects of watersheds on the surrounding

environment in terms of the biology, water quality, and economic importance of streams.

• Identify different stream features based on their geological formation due to erosion and deposition.

• Develop an experiment to test how human actions can modify stream morphology in ways that may, in turn, impact riparian ecosystems.

Time Requirements Preparation ...................................................................... 5 minutes, then let sit overnight Activity 1: Creating a Stream Table ................................ 60 minutes Activity 2: Scientific Method: Modeling Human Impacts

on Stream Ecosystems .................................. 45 minutes

2 Carolina Distance Learning

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Key Personal protective equipment (PPE)

goggles gloves apron follow link to video

photograph results and

submit

stopwatch required

warning corrosion flammable toxic environment health hazard

Table of Contents

2 Overview 2 Outcomes 2 Time Requirements 3 Background 9 Materials 10 Safety 10 Preparation 10 Activity 1 12 Activity 2 13 Submission 13 Disposal and Cleanup 14 Lab Worksheet 18 Lab Questions

Background A watershed is an area of land that drains any form of precipitation into the earth’s water bodies (see Figure 1). The entire land area that forms this connection of atmospheric water to the water on Earth, whether it is rain flowing into a lake or snow soaking into the groundwater, is considered a watershed.

Water covers approximately 70% of the earth’s surface. However, about two-thirds of all water is impaired to some degree, with less than 1% being accessible, consumable freshwater. Keeping watersheds pristine is the leading method for providing clean drinking water to communities, and it is a high priority worldwide. However, with increased development and people flocking toward waterfront regions to live, downstream communities are becoming increas- ingly polluted every day.

From small streams to large rivers (hereafter considered “streams”), streamflow is a vital part of understanding the formation of water and landmasses within a watershed. Under- standing the flow of a stream can help to deter- mine when and how much water reaches other areas of a watershed. For example, one of the leading causes of pollution in most waterways across the United States is excessive nutrient and sediment overloading from runoff from the landmasses surrounding these waterways. Nutrients such as phosphorus and nitrogen are prevalent in fertilizers that wash off lawns and farms into surrounding sewer and water systems. This process can cause the overpro- duction of algae, which are further degraded by bacteria. These bacteria then take up the surrounding oxygen for respiration and kill multiple plants and organisms. A comprehen- sive understanding of the interaction between streams and the land as they move downstream to other areas of a watershed can help prevent pollution. One example is to build a riparian buffer—a group of plants grown along parts of a stream bank that are able to trap pollutants and absorb excessive nutrients; this lessens the effects of nutrient overloading in the streambed. (A riparian ecosystem is one that includes a stream and the life along its banks.)

Sediment, which is easily moved by bodies of water, has a negative effect on water quality. It can clog fish gills and cause suffocation, and the water quality can be impaired by becoming very cloudy because of high sediment flow. This can create problems for natural vegetation growth by obstructing light and can prevent animals

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Figure 1.

Snow

Rainfall

Precipitation

Overland flows

Underground sources

STREAM MORPHOLOGY

Background continued from visibly finding their prey. Erosion also has considerable effects on stream health. Erosion, or the moving of material (soil, rock, or sand) from the earth to another location, is caused by actions such as physical and chemical weath- ering (see Figure 2). These processes loosen rocks and other materials and can move these sediments to other locations through bodies of water. Once these particles reach their final destination, they are considered to be depos- ited. Deposition is also an important process because where the sediment particles end up can greatly impact the shape of the land and how water is distributed throughout the system (see Figure 2). Erosion and deposition can occur multiple times along the length of a stream and can vary because of extreme weather, such as flooding or high wind. Over time, these two processes can completely reshape an area,

causing the topography, or physical features, of an entire watershed to be altered. Depending on weather conditions, a streambed can be altered quite quickly. Faster moving water tends to erode more sediment than it deposits. Deposi- tion usually occurs in slower moving water. With less force acting on the sediment, it falls out of suspension and builds up on the bottom or sides of the streambed.