Drought

Online Lesson Plan

lrKathyDrought

Suppose one year the normal rain failed to come in Nebraska. Then year after year the rainfall was far below normal resulting in a prolonged drought. What would that be like? How would we, as a school, be affected? Would our fountains work? What would the playground look like? This lesson looks at the effects of water on soil and, by extension, the effects on plants and the agricultural economy.

Lesson Plan by Kathy Jacobitz, science education consultant, Pawnee City, Nebraska.

Objectives

standards02Suggested grade level – 5th-8th.

  1. Students will gain knowledge about the impact of drought in agriculture.
  2. Students will investigate soil types, water flow, and various erosion conditions which occur during a drought.
  3. Students will explore changes in farming practices which changed as a result of education in the late 1930s.

Introduction

pests0201The 1930s was a time in our history with a prolonged drought. What happened to life on the farm during the 1930s drought? What part of the farm was affected first?

Nebraska has experienced numerous periods of dry conditions. The 1800s had dry periods as well as the 1860s and 1880s. The Dust Bowl period was during the 1930s and greatly impacted life in Nebraska; especially in rural areas. Another period of drought occurred from 1954-1956. Students should investigate the impact of each drought period on the people of Nebraska.

Nebraska soils vary in composition from the western to eastern parts. Students will investigate soil composition and the ability of water to flow through it. The students will examine runoff from fields and begin to understand about groundwater.

Erosion due to the impact of materials on the earth’s surface will be explored through investigations. Wind erosion and control of the wind will be addressed in the study.

 

Resources

  • Wessels Living History Farm page Drought
  • Wessels Living History Farm page The Dust Bowl
  • Wessels Living History Farm page No Water, No Crops
  • Wessels Living History Farm page Calling Off School for Dust
  • Wessels Living History Farm page Red Dust from Oklahoma
  • Sink or Swim, The Science of Water, by Barbara Taylor.
  • “Magic School Bus” videotapes 1.) Wet All Over and 2.) At the Waterworks
  • Aquatic Wild – How Wet Is Our Planet?
  • Nebraska’s Climate: Past and Future, by Michael Palecki
  • An Agricultural and Social History of the Dust Bowl, by D. R. Hurt
  • PBS Film – “Surviving the Dust Bowl”
  • Soil Science Simplified, by Milo I. Harpstead
  • Water and Soil Test Kits

 

Process

Students should perform a KWL Chart – What We Know / What We Want to Know / What we Learned – about soil. Each student needs to make a journal entry. Follow the individual KWL with a class KWL.

Soil may be studied for various things however we will concentrate this unit on water movement through the soil. Percolation refers to the speed with which water soaks into the soil. Soils that are more porous and composed of sand will drain fairly fast while soils having higher concentrations of clay results in slower movement of water. The drainage characteristics of the soil affect the kind of plants and animals living in the area. Soil acts as a sponge to soak up excess water. Sand, silt and clay make up most of the mineral content in soil.

Question/Problem:

How fast will water soak into the soil?

Hypothesis:

Controls:

Variable:
Materials Needed

  • Zip lock bags for soil samples.
  • A metal coffee or juice can. All cans will need to be the same size.
  • A watch with a second hand or a stopwatch.
  • A meter stick or ruler with centimeter gradations.
  • A container to carry water to a test location.
  • Sharpened pencil with an eraser.
  • Cheesecloth.
  • Scale.
  • String.
  • pH paper.
  • Deionized water.
  • Eyedropper.
  • 2 one-liter bottles.

 

Procedure

Percolation Test:

Select the site or sites for the percolation test. It works well for this study if you select sites such as farm fields, yards, pastures, playgrounds, etc. Make observations of the area(s) selected and write them in the journal.

Take a zip lock bag to the site and bring 1/2 to 1 cup of soil back to
the classroom. The soil needs to be closed up in the zip lock bag to prevent evaporation of moisture from the soil sample. You could locate a study buddy in Western Nebraska and ask them to perform the same test on their soil and share results.

Prepare the test can by removing both the top and bottom of the can. Have an adult help with the removal of the can lid and base. Paint or mark with a waterproof marker inside the can a line at the 10 cm distance from an opening. To conduct the test, push the can into the ground up to the 10cm mark. This will leave the top of the can above the ground. Then fill the can to the top with water and time how long it takes for 10 cm column of water to be absorbed into the ground. Record the measurement. Do you think more tests are needed to get an average for the area? Remember, move the can to an area nearby before you test again, because your present test site now has wet soil. Plot the measurements from various areas and discuss the results in class.

Compaction Test for Soil:

Use an ordinary sharpened pencil with an eraser for this test. Push the pencil into the ground with the palm of your hand on the eraser until you cannot push it any deeper. Pull out the pencil and measure how many cm the pencil penetrated the soil. Record the compaction test data for each site tested for the percolation test. Soil can get compacted in various ways, by humans and animals, vehicular traffic, or the weight of rain or snow. Check other locations and record measurements in the journal. Bring the data to school for a discussion on soil compaction. Ask your students if different types of soil compact easier than others.

Soil Moisture Test:

Take the bags of soil each student brought in from their test sites and weigh it. Don’t forget to subtract the weight of the bag. Also decide if you are going to use 1/2 cup or 1 cup of soil for this test. Record the weight in the journal. Weigh the soil sample after it is allowed to dry out. Calculate the weight of the water that evaporated. Where did it go? Water cycle discussion could follow this investigation. Express the weight of water evaporated as a percentage of the weight of the original soil sample. Your students will end up with the percent of moisture content in their samples. Record results and graph the data.

HINT: This works well if you have the students measure out exactly 100 grams of soil for the test. Why will this help?

Water Holding Capacity of Soil:

Soils have differing capacities to retain or hold water. The ability of a soil to hold water is called its water holding capacity. This ability is based largely on the soil particle size and the amount of organic material in the soil.

To measure the water holding capacity of your soil, use the dry soil samples your students used for the moisture content test. Measure out 100 grams of each of the dry soil samples. Place the sample in the middle of a square of cheesecloth. Fold each corner toward the middle and tie it with a string so you have a small bundle. Leave an extra foot or so of string so you can hold on to the string. Weigh the whole package; dry soil, cheesecloth, and string. Record the data in the journal. Holding the string, dip the bundle of soil into a container of water. Leave it until it will absorb no more water. Lift the bundle of soil up by the string and let the excess water drain from the bundle until no more will drain out. DO NOT squeeze the water out. Weigh the wet bundle, including the string and cloth. Calculate the amount of water the 100 grams of soil can hold. This is a measure of the water holding capacity of the soil sample. Record the results. Share the data for all the soil samples. Discuss and apply the results. Were any differences noted in the samples?

Why?

What is the difference between water holding capacity and the soil moisture content?

Why? (Journal response and class discussion.)

Soil pH:

pH measures basic or acidic condition of the soil. The pH of the soil influences the kind microorganisms and plants growing in it.

To test the soil samples for pH, put 50 ml of the soil in a paper cup and add an equal part of deionized water. Stir the mixture. Dip a piece of pH test paper into the mixture. Remove the paper, wait for it to change color (about 10 seconds) and compare it to the color chart on the pH paper. Record the pH level in the journal and report to the class. Discuss the pH results from the soil samples. Were the pH results all the same or were there differences? What pH does corn like best?

Tactile Soil Examination of Dry Soil by Touching

Examine the dry soil particles with your fingers. Record the observations in the journal. Using an eyedropper add a small amount of water to the soil sample and rub the moist soil between your fingers.

  • Does it feel gritty? Sand
  • Does it feel smooth, soapy, greasy or slippery? Silt
  • Does it feel sticky? Clay

Record the results in the journal and share your results in class. Place this chart on the board and ask students to respond to its meaning in their journal. Discuss with the class.

Particle Size:
Sandy Soil – Largest Particles
Silt Soil – Smaller Then Sand Particles
Clay Soil – Smallest Particles

Additional Investigations:

Design a mixture of sand, gravel, and clay that will allow for a good water holding capacity and compaction yet it will allow water to pass through to ground water (percolation). Explain the process of this investigation in the journal using the scientific investigation form (Click Here). Record all data on a chart, table and graph in the journal. Prepare a scientific paper or display about the investigation

Teacher Demonstration or Assessment

Obtain 250 ml of sand, 250 ml of pea size gravel, 250 ml of clay and three large funnels. Force a piece of cheesecloth into the top of the spout of each funnel. Place the sand into one funnel, pea size gravel into the second funnel and clay into the third funnel. Students need to make predictions about what they think will happen and why. Pour equal amounts of water (200ml) onto the materials contained in the funnels. Time how long it takes the water to flow through the materials. Record all the data in the journal.

Questions:

  1. Which material did the water flow through the fastest? Why?
  2. What were the controls and variable in the investigation?
  3. You discover three rock units in Nebraska: gravel, sand, and clay, all containing the same quantity of water. Which would you drill a well in? Why?

Learning Advice

Be prepared for spills since the students are working with soil and water. Make sure students understand how to weigh a sample on a scale. Can they explain why the containers need to be weighed?

Conclusion

Drought conditions result in less water in the soil. Droughts directly effect agriculture since plants need water to grow. During the 1930s crops were damaged by deficient rainfall, high temperatures, and high winds, dust storms, and insect infestations that all causing financial loss to farmers. The lack of precipitation affected wildlife, plants and created water shortages for domestic needs. The effect of the Great Plain’s drought caused economic and social declines throughout the United States.

Assessment

Click on the following to view assessment suggestions:

  1. KWL Chart pre and post.
  2. Journal Assessment Rubric.
  3. Rubric for Scientific Research.
  4. Assessment Checklist for the Scientific Research.
  5. Venn Diagram.
  6. Rubric for the Research Paper.
  7. Rubric for Group Work.

General Notes

Answer the following questions:

  1. What was the Dust Bowl?
  2. How much rain is normal?
  3. What was the rainfall amount during the time known as the “Dust Bowl”?
  4. What part did farming practices of the early 1900s play in creating the Dust Bowl?
  5. How much rain is required for a wet period?
  6. What is considered a dry period?
  7. How does rainfall and temperature of the 1920s compare to the 1930s and 1940s?
  8. What were the weather patterns prior, during and post Dust Bowl?
  9. Are there cyclical wet and dry period in the Great Plains area?
  10. Will there be another Dust Bowl?

Language Arts:

The Grapes of Wrath by John Steinbeck was written about the 1930s. Read the following statement from his book.

“And then the disposed were drawn west from Kansas, Oklahoma, Texas, New Mexico; from Nevada and Arkansas, families, tribes, dusted out, tractored out. Car loads, caravans, homeless and hungry; twenty thousand and fifty thousand and a hundred thousand and two hundred thousand. They streamed over the mountains, hungry and restless as ants, scurrying to find work to do – to lift, to push, to pull, to pick, to cut – anything, any burden to bear, for food. The kids are hungry. We got no place to live. Like ants scurrying for work, for food, and most of all for land.”

Write an interpretation of the above statement and write your own story about living during the 1930s.

Drought data is available at The University of Nebraska-Lincoln Drought Mitigation Center. [http://www.drought.unl.edu/dm]

Extensions

lrTreeRings2Dendrochronology Investigation about the Drought:

Trees are some of nature’s most accurate timekeepers. The growth layers in a cross section of a tree are called tree rings. Tree trunks record evidence of local conditions, such as floods, droughts, insect infestations, fires, and lightning strikes.

Tree growth depends on the availability of water. Scientists use tree ring patterns to reconstruct regional patterns of drought and climate change. Andrew Ellicott Douglass, a dendrochronoligist, began his studies in the 1900s.

Archaeologist use tree rings to date timber from log cabins and Native American pueblos by matching the rings from the cut timber of the homes to rings in very old trees nearby.

Tree rings record seasonal changes in the tree’s surroundings. The rapid growth during the warm season makes a wider ring, light in color where as the slower growth during the cold season produces a narrow, dark band.

To use tree ring analysis you must know when the tree was cut down and work from the outside to the center counting rings to discover the age of the tree. I suggest obtaining tree cuttings from local individuals who cut trees for firewood or remove trees for a living. If not available use the tree ring provided for practice.

The youngest tree ring growth areas are closest to the bark while the ring closest to the center is the oldest ring. Neither the outer bark nor the central pith layer of a sample is counted in determining the age of a tree. Use the tree truck sample to practice the process involved with dendrochronology. This tree was cut down in 1949 near York, Nebraska. Locate and label the dry years with the letter D. Identify a scar left by fire with the letter F. Place a W on the wet years. What was the diameter of the tree in 1937? Mark the drought years of the dust bowl with an X.

Dendrochronologists seldom cut down a tree to analyze its rings. Instead, a core samples are extracted using a borer that is screwed into the tree and pulled out, bringing with it a straw size sample of wood about four mm in diameter. The hole in the tree is then sealed to prevent disease.

Materials:

  1. Tree cross sections if available for your local area.
  2. Tree charts of cross-sections.
  3. Make up a tree core strip of paper.
  4. Adding machine tape.
  5. Almanacs as reference material for social and scientific events.

Using your tree core sample or the one above asking students locate wet years, dry years, and the age of the tree. The tree core can be reproduced on the adding machine tape by using a larger scale to represent the tree core. Double or triple ratios work well for the comparison study.

Record things that happened during the life of the tree such as:
Inventions, presidential elections, sports achievements, books published,
top ten songs, birthdays, etc. You may have students color the timeline.
Plus illustrate it with drawings, photographs or clippings from newspapers.

The timeline represents the growth rings when placed on a three meter strip of adding machine tape. It would be another math ratio for the students to explore if you do not such want to double or triple your tree core sample.

What happened in your area during the life of the tree? Write a story about life from the trees point of view.

Additional Tree Investigations

  1. Measure the circumference of several trees, calculate diameter and radius.
  2. Measure the shadows of trees. Design a way to measure the height of a tree without climbing it. Hint: you will need to make a triangle at a distance from the tree.
  3. Pretend you are a tree. Write about the services you provide for humans, animals and other plants.
  4. How cool are tree shadows?
  5. Write the Arbor Day Foundation for information about Arbor Day.
  6. Write a story about what it would be like to be any of he parts of a tree.
  7. Read:

The Giving Tree by Shel Silverstein
Eyewitness Trees by Alfred Knoff
The Great Kapok Tree by Lynn Cherry
Once There Was A Tree by Barbar Buin

Additional Investigations

Erosion:

Erosion is a natural process by which rock and soil is broken loose from the earth’s surface at one location and moved to another. One of the most harmful effects of erosion is robbing farm land of productive topsoil.

1. Your job is to control erosion on the bank of a stream. It is claimed a large a combination of protective leaves and roots will prevent erosion. Others believe a compact network of roots will hold the soil in place. How can your students find out if either of the above ideas is correct? This would work great as an assessment for the soil investigation. Students design and carry out the investigation.

2. Soil conservation services during the 1930s taught farmers ways to slow erosion and protect the soil. Compare and contrast how the following methods helped with erosion control: a.) Planting trees for windbreaks; b.) Contour plowing; c.) Strip cropping; d.) Terracing; and others your students discover through their research.

3. SPLAT, SPLAT, SPLAT!!!

Change is inevitable on the earth’s surface. All things, living or nonliving change over time. Sometimes it is a quite evident, such as the eruption of a volcano or something very small like the falling of an object like rain drops to the surface of our planet. We can make observations of changes that take place both quickly and slowly.

The students will make observations and measurements of the impact of objects hitting the surface of the earth. Students will investigate the role of gravity as a force through this investigation.

It works well to use a kitty pan sized container to hold soil or other selected material to represent the unprotected surface of the earth. You can use various materials to drop onto the pan area; water, marbles, ping-pong balls, tennis balls, etc. Questions:

1. Does the distance the object falls affect the results of impact on
the surface?
2. Does the material the object impacts make a difference in the
results?
3. Does the size or mass of the object falling cause a different
result upon impact?
4. Where and when were the earth’s largest impact craters made?
5. Compare the diameters of earth’s largest craters.
6. Investigate through research the meteor crater found in Arizona. Why has erosion not destroyed the crater’s features?
7. What effect does impact of rain have on the earth’s surface?
8. What effect does hail cause on the surface of the earth?
9. Why do giant meteors make such big craters and cause massive impacts on our environment?
10. What direct and indirect effects might there be on living things when erosion occurs?
11. Write a story relating the practices of contour plowing with contour painting.

Math Extension:

Surface Area and Volume:

To begin to get a feeling for the surface volume relationships and how they may be determined for an organism you will determine the surface volume relationship of leaves and fruit. Leaves and fruit are used because determining their surface areas and volumes are fairly easy and don’t require any fancy equipment.

You will need the following for the investigation:

1. Pick a selection of leaves from trees and shrubs from your area.
2. You will need a dozen different leaves with
several of each kind. Pick a range of
sizes and be sure to note the name of the tree or shrub for each
leaf if possible.
3 . Obtain fruit: apples, lemons, plums, bananas, grapefruit, and
grapes – provide a selection of different sizes.
4 . A ruler that measures in cm.
5 . A balance that will weigh to the nearest 0.01 grams.
6 . Scissors.
7 . Pencil.
8 . Several sheets of identical kind of paper.
9 . Graph paper.
10 . Graduated cylinders.

Determine the surface area of a leaf:

Determining the surface area of a leaf seems difficult because of the complicated shape and the presence of toothed or scalloped edges. This difficulty is easily overcome by the following procedure. Trace the leaf on a piece of paper with a pencil and cut out the tracing with scissors. On a similar paper draw a small square having 10 cm sides. This square will have an area of 100 square cm or 10,000 square mm. Weigh square of paper to the nearest 0.01 gram. Using this weight compute the weight of one square cm of paper. Now weigh the cutout tracing of your leaves and record the weights. Using the value for the weight of one square cm of paper, calculate the area of your cutout. Don’t forget to double this area because your cutout and leave has a least two surfaces – a top surface and a bottom surface. A slick variation is to take the leaves to the copy center and photocopy them. Cut the photocopies. This procedure saves the labor of tracing the leaves. Be sure to use a sample of photocopy paper for your 100 square cm calibration sample.

Determining the Volume of a Leaf:

The volume will be done by water displacement. The idea is you will determine the volume of water displaced by the leaf. Carefully roll up the leaf and slip it into a graduated cylinder. Best results are obtained when the smallest possible cylinder is used. Fill up the cylinder to a level that comfortably covers the rolled up leaf. Carefully remove the leaf making sure all of the water stays behind in the cylinder. Now note the new volume of water – it should be less then the original volume. The difference between these volumes is the volume of your leaf. If you have tiny leaves, simple combine them in the cylinder and determine their average volume.

What to do with the data:

For each leaf analyzed you will have a set of data: a surface area and a volume. For each leaf these data will be plotted on graph paper. Plot the surface area on the X-axis of your graph paper and plot the volume on the Y-axis of your graph. Each leaf will be represented by a point on the graph. NOTE: You will have to fiddle around a bit so that the number of graph divisions of your X and Y-axis are sufficient to plot your larger leaf. Don’t scrimp and make a tiny, squeezed up graph – use as much of the paper as possible. When you get finished plotting your data you have what scientists call a “scatter plot”. Now the fun: Using your cm ruler, try and draw a straight line using your data points as an approximation. This is the real fiddling. Do most or all of the points fall on a straight line? Look for one or more data point’s way off the line. How do you account for these discrepancies? This is the biology part of the data.

Now, can you devise a way to construct a graph for the fruit? Explain the data.

Questions:

1. Why are most fruit round but bananas are elongated?
2. What shape are the insides of oil filters and how can they filter so much for so long?
3. Why are elephant and rabbit ears shaped the way they are?
4. Why are ice cubes made cubical?
5. Why are graduated cylinders tall and skinny?
6. Why are beakers short and wide?
7. What makes better fasteners, nails or screws?
8. If a sphere maximizes surface area: volume ratio, why aren’t more containers and structures built like spheres?
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