Rutgers University Problem

How does your watershed impact the ocean?

Investigation Explanation Journal COOL New Terms Index Unit Plan Back to COOL Classroom

Hudson River Plume

1) Introduction

Before starting this lesson, engage students in a brief discussion about what happens when fresh river water enters the ocean.

Then, ask your students what a watershed is. Elicit students’ ideas about watersheds but do not correct any misconceptions at this point.

2) What is a watershed?

Have your students explore the water cycle animation.

You may want to review the different parts of the water cycle with them before moving to the next page.

3) Water in the Watershed

Have your students explore this animation.

It is important for students to understand that all the water falling in the same watershed will eventually flow to lowest point in the watershed, like a river, and then into the ocean. (This is similar to pouring water along the sides of a bowl or funnel.)

4) STOP: Lab

This activity takes about 20 minutes. It can be done after quickly viewing the beginning on a whiteboard as a whole class. During the activity, make sure students realize that the high areas are the bounaries of a watershed. That the water flows down the sides to a common basin on either side of the "mountain top."

5) Hudson Watershed

The students will spend some time investigating the Hudson River Watershed. There is a Google Earth Tour under the Teacher Resources tab on this page.

6) What is the Hudson River plume?

Students may choose any color(s) to paint their plume. Later on in the unit they will be asked to redraw their plume diagram using information that they have learned and will want to have their original drawing to compare to. After students are satisfied with their diagrams they should print them out as they cannot save their drawings in their online journal. (Some computers may allow you to "Print to PDF," or something similar, which would save a digital copy independent of this web site.)

Students will explain the reasoning behind their drawings on the following page.

7) Paint plume write-up

8) STOP: Class Discussion

Ask some students to share their drawings.

Students should explain what they drew and why they think the water will behave that way (their response to the journal question can serve as a jumping board for this discussion). Emphasize to students that they need to explain the reasoning behind their model – why they think what they think. (They can use examples from everyday experiences as evidence to justify their model). Questions like “why will it look like that” and “how do you know” can help move this discussion along.

Do not correct any misconceptions at this point, merely surface their prior understandings. This experience will demonstrate how we modify our ideas as we gain more knowledge. Eventually students will learn to support their ideas with evidence.

9) Plumes

In order to help students understand the properties of the Hudson River Plume we will explore properties of a more familiar plume, smoke. Students use their observation skills to determine the characteristics (again, please don’t give them the answer). The answer will be detailed in upcoming pages.

10) Smoke plume explanation

11) Smoke plume in the wind

After students have answered the journal question, review the properties of a plume, namely…

  1. Particles stay closer together at the origin and spread apart as they move away
  2. A plume is an area containing the same type of particles
  3. All the particles tend to move together in the same direction

12) STOP: Lab

The Creating a Plume Activity will introduce students to a plume in liquid. The characteristics of a plume should be observable.

This activity can be done quickly (15 minutes) with just one color or expanded to have students carefully observe what happens to each color. There are slight differences in how each color behaves as it drops into water.

If you don’t have time for this activity, the video on the next page does a good job of showing it.

13) Food Coloring Demo

Have a brief discussion with your students about why the food coloring plume stayed together. This is essentially a review of plume characteristics.

14) Redraw Plume

In this activity, students can still choose any color to paint their plume. However, they should have an explanation for why they chose these colors and what each color in their plume picture represents.

Students may not have prior knowledge of the colors used by scientists (i.e. cold water = blue and warm water = hot) because they have not seen satellite images. They should demonstrate in their drawing that the fresher, warmer plume water will extend out into the saltier, colder ocean.

15) STOP: Class Discussion

Have students discuss their answers to the journal question. Make sure that they all understand that the freshwater that flows out into the ocean will behave like a plume, and will stay together.

Have students compare their initial and final models (drawings) of the plume. This will help them see how much they have learned. Tell the students that scientists revise their ideas as well and that after conducting experiments scientists may change their initial models based on new evidence.

16) Satellite images

These are two satellite images of the Hudson River Plume. Look at these images with your students and identify the plume. Help them connect their observation of the food coloring demonstration with the plume as shown here.

This is a great place to emphasize that scientists compare their explanations, called models, to real data in order to determine how well their explanations account for the evidence.

These images can be somewhat confusing. For a detailed explanation see the resources tab.

17) Sea Surface Temperature

If students are confused about this image, have them click on the link to learn more about reading SST maps for a quick explanation.

18) Plume Path

Ask the students where the material for the new plume (see explanation below) came from.

Help the students understand that the river water and the materials dissolved in it continuously flows out into the bay.

There is a good paper activity under the Related Activities tab.

19) STOP: Group Discussion

Students should have a basic understanding already that river water is fresh and ocean water is salty. They may or may not know that river water is warmer than cold ocean water. Again, this is a time when you don’t give them the answer, but let them practice thinking as a group.

20) Why do plumes stay together?

21) SST observations

Discuss with your students how they think temperature and salinity impact the mixing of river and ocean water. Prompt students to explain their ideas and justify them with evidence from their everyday experience (ask "how do you know that" and "why do you think that").

In the following pages, there are video demonstrations of how temperature and salinity affect the density of water.

22) STOP: Lab

Layering Liquids shows how less dense liquids float on one another.

The Density Jar Demo demonstration only takes about 10 minutes, but helps students grasp the idea that the more stuff (mass) there is in a given space (volume) the higher the density.

23) Warm & Cold water meet

Before students watch the video, have them predict which type of water (warm or cold) they think is denser and thus will sink to the bottom and form the bottom layer. Make sure they give reasons to support their answers.

A detailed explanation of why warm water is less dense is provided under the Resources tab.

24) Fresh & Salt water meet

Before students watch the video, have them predict which type of water (salty or fresh) they think is more dense and thus will sink to the bottom and form the bottom layer. Make sure they give reasons to support their answers.

Salt water contains dissolved salt molecules, meaning there are more particles in the same volume of salt water than there is in pure fresh water. So salt water is more dense.

25) Density Explanation

26) Ocean/River Video

Before students watch the video, have them predict which type of water (cold salty or warm fresh) they think is more dense and so will sink to the bottom and form the bottom layer. Make sure they give reason to support their answers.

27) Density check

Make sure the students understand why ocean water is more dense than bay water, and why bay water is more dense than river water.

Recall that river water is mostly freshwater with a tiny amount of dissolved materials and salts. It is much less dense than bay water which is brackish (part salty and part fresh), while ocean water contains a lot more salt making it the most dense of the three.

While temperature can also affect the density of water, in most estuaries it is the the salt difference that has the greatest impact.

28) Plumes tend to stay together

29) Tracking question

Discuss students’ answers. Make sure to prompt them to draw on what they’ve learned about water density in the previous pages to address this question.

Scientists are also able to make measurements from boats and can use differences in density (salinity and temperature) to track the plume water.

Students may suggest other viable options like differences in water color, clarity and sediment concentrations (like sand).

30) Meet Brian Gaas

The Learn more about is a popup which uses graphics to give general information about the LaTTe experiment ~ scientists placed dye in the Hudson River to show its flow pattern in the bay and ocean. It is outstanding!

There are more sites which give details listed under the Resources tab.

31) Why are plumes important?

This graphic is from the beginning of the unit. Students have spent some time learning about plumes, so now we are going to look at why plumes are important.

Students do not have to walk through the entire animation at this time. It’s just to remind them of how the water flows in the watershed.

32) What's in the Water?

Notice that water flows from all directions, flowing down the mountains (red = higher elevations) of the Hudson River Watershed and into the Hudson River. All this water eventually travels past New York City and into the Atlantic Ocean.

Some students may think that water always flows from the top of the map to the bottom. However water flows downhill, and the direction it flows depends on the underlying topography (elevation level) of the watershed.

33) Land Use

34) Overlay Maps

Have students notice that cities tend to be located where rivers meet. And also that agricultural (farmland) areas tend to be near the river.

Discuss with your students why that might be.

In essence this is a social studies issues, but it merits a brief discussion here.

35) Human Impacts

Too much nitrogen in the water leads to eutrophication (which will be explained in detail later).

Have students explain how each of the phenomena described in the bubbles affects the watershed. Also, ask students if they think anything they do in their personal lives might effect the watershed and ultimately the ocean.

In particular, have them explain how they think car exhaust ends up in the watershed. (Particles in the air can be dissolved by water in the air and eventually fall out as rain and thus end up in the watershed.)

36) Local Pollution Sources

Have the students think about an example of pollution that might be occurring near their school or surrounding community. You may want to discuss how such a pollution source can be reduced.

What do they think this pollution is doing to the plants and animals in the river and eventually those in the ocean.

37) STOP: Class Discussion

Before moving on, discuss students’ response to the journal question.
Make sure students backup their answers with good reasons.

You can use Google Earth to zoom in, out and around various parts of the Hudson River Watershed or your own local watershed. You can download this KMZ File which highlights several key locations around the watershed. Students can compare elevations of mountains and rivers to confirm watershed boundaries and can investigate possible sources of point and non-point pollution.

38) What is eutrophication?

You may want to point out to your students that not all pollutants are overly toxic. For example, fertilizer, one of the most common pollutants is actually good for plants. However, too much of a good thing can be bad. On the next page, students will explore this effect.

39) Eutrophication Story

This animation allows students to explore the process of eutrophication and the creation of a dead-zone (oxygen deprived area that cannot support much life). Since this process occurs at multiple levels of organization – molecular, microscopic, and macro – the animation provides views for each of these levels.

Have students explore the process with the animation, ask them to view all views available.
When they are done bring the class together and discuss the process in detail. Have students explain the process at the different levels. You may want to have them create their own diagram models of this process.

40) Explanation

41) Final Project

In order to provide students with a more authentic audience for their explanations, have students develop brochures or information packets that explain how human activities in their watershed affect water quality in the river and ultimately the ocean.

These brochures can be disseminated to other students in the school or broader community.

Check out the example rubric for how to grade the final projects.

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