Water for Schools
Menu

Lesson plan Grade 11 Social Studies & Civics

From the Dust Bowl to the Center Pivot: Ryeland County Water

Students trace eighty years of a fictional High Plains county's irrigated acres, population, and water levels, then explain how pump technology reshaped who lived there.

Objectives

  1. Students will calculate percent change and average annual rates from an eighty-year county data table.
  2. Students will explain how a farm technology spread across a region and changed its population distribution.
  3. Students will describe the reciprocal relationship between groundwater withdrawal and the land uses that withdrawal supports.

Vocabulary

Aquifer
An aquifer is an underground layer of rock, sand, or gravel that holds water in the tiny spaces between its grains. Wells reach down into aquifers to bring water up to the surface.
Drawdown
Drawdown is how far the water level in a well drops when a pump pulls water out. The harder and longer you pump, the bigger the drawdown gets.
Acre-foot
The amount of water it takes to cover one acre of land, about the size of a football field, one foot deep. Western states use acre-feet to measure large amounts of water.

Also: center pivot, saturated thickness, out-migration, Soil Conservation Service

Teacher overview

The dust storms of the 1930s are usually taught as the end of a story about the southern Plains, yet the more consequential change came after the war, when rural electrification and cheap diesel made deep-well turbine pumps practical and the center-pivot sprinkler spread across counties that had been dryland wheat country. This lesson uses eighty years of invented data from Ryeland County, a fictional High Plains county sitting on the fictional Steadman Aquifer, to connect a farm technology to population, land use, and groundwater levels. Students commonly assume that a county whose farm output grows must also be gaining people, when mechanized irrigation across much of the Plains raised production while steadily reducing the number of workers a farm needed.

Procedure

Hook, 5 minutes. Show the class the county data table with the population column covered. Ask students to predict what happened to the county's population between 1940 and 2020, given the irrigated acreage figures they can see. Record two or three predictions on the board and leave them there.

Background, 12 minutes. Deliver a short account of the sequence, keeping it to the chronology. Severe wind erosion in the 1930s brought federal soil conservation work to the southern Plains, including terracing, contour plowing, and shelterbelt planting, and Congress created the Soil Conservation Service in 1935 to carry it out. Those measures addressed the soil rather than the water supply. After the Second World War, electric and diesel power reached farms that had relied on windmills, deep-well turbine pumps became affordable, and the center-pivot sprinkler patented in the early 1950s spread quickly because it could irrigate uneven ground with far less labor than ditch irrigation. Under much of the region lies the High Plains Aquifer, which is recharged slowly by rainfall and in its southern reaches has been drawn down faster than it refills.

Data analysis, 13 minutes. Uncover the population column. In pairs, students plot irrigated acres and depth to water against the decade, then describe in writing the shape of each curve and the decade at which each turns. Ask two pairs to report the turning points they identified before moving on.

Handout work, 20 minutes. Students complete the eight handout items. Circulate during items 2 and 3 and check that students divide the change by the starting value for percent change and by the number of years for an annual rate. Use a quick poll before item 6: ask how many feet are in eighteen inches, and if fewer than three-quarters of the class answers one and a half feet, work the conversion on the board before students continue.

Closure, 10 minutes. Return to the predictions on the board. Ask students to write one paragraph explaining what the class got right and wrong, using at least two figures from the handout. Collect these as the exit ticket.

From the Dust Bowl to the Center Pivot: Ryeland County Water — Grade 11 Social Studies & Civics
Name: ____________________________ Date: ______________

Student Handout

Ryeland County and the Steadman Aquifer are fictional, and every figure in this table was invented for this lesson.

Decade Irrigated acres County population Average depth to water, in feet
1940 3,000 9,400 62
1960 48,000 11,200 74
1980 156,000 12,600 101
2000 205,000 10,300 138
2020 198,000 8,100 176
  1. Ryeland County irrigated 3,000 acres in 1940 and 156,000 acres in 1980. Calculate the increase in irrigated acres over that period.
  2. The county irrigated 48,000 acres in 1960 and 156,000 acres in 1980. Calculate the percent increase between those two years.
  3. Average depth to water was 101 feet in 1980 and 176 feet in 2020. Calculate the average yearly increase in depth to water across those 40 years.
  4. County population was 12,600 in 1980 and 8,100 in 2020. Calculate the change in population, and state whether it is an increase or a decrease.
  5. In 2020 the county irrigated 198,000 acres and had 8,100 residents. Calculate the irrigated acres per resident, rounded to the nearest tenth.
  6. One center pivot in Ryeland County covers 132 acres and applies 18 inches of water over a season. Eighteen inches is 1.5 feet. Calculate the acre-feet of water that pivot applies in a season.
  7. One acre-foot equals 325,851 gallons. Using the 198 acre-feet from item 6, calculate the gallons one pivot applies in a season.
  8. In three or four sentences, explain how the county's irrigated acreage could stay near its peak between 2000 and 2020 while its population fell.

From Water for Schools (waterforschools.org). This material is in the public domain (CC0) and may be copied, edited, and shared freely.

Answer Key
  1. Answer: 153,000 acres. Subtract 3,000 acres in 1940 from 156,000 acres in 1980.
  2. Answer: 225 percent increase. The change is 156,000 minus 48,000, or 108,000 acres, and 108,000 divided by 48,000 is 2.25.
  3. Answer: 1.875 feet per year. Depth increased by 75 feet, from 101 to 176, across 40 years, and 75 divided by 40 is 1.875.
  4. Answer: A decrease of 4,500 people. Subtract 12,600 from 8,100 to get negative 4,500, which is a loss of 4,500 residents.
  5. Answer: About 24.4 acres per resident. Divide 198,000 acres by 8,100 residents to get 24.444, which rounds to 24.4.
  6. Answer: 198 acre-feet. Multiply 132 acres by a depth of 1.5 feet.
  7. Answer: 64,518,498 gallons. Multiply 198 acre-feet by 325,851 gallons per acre-foot. Accept about 64.5 million gallons.
  8. Answer: Center pivots and larger equipment let a smaller number of operators farm the same ground, so labor demand fell while output held. Farms consolidated, young workers left for jobs elsewhere, and the businesses that served a larger farm population closed. Accept any answer that separates output from employment and names mechanization or consolidation as the reason.

Differentiation

Support

Give these students the table with the differences for items 2 and 3 already computed, so their work on those items is limited to the division steps. Provide a worked example of percent change using the 1940 to 1960 rows before they attempt item 2, and allow the plotting task to be completed with only the irrigated acres column.

Extension

Ask these students to project the fictional depth to water for 2040 using the rate from item 3, then to explain in a paragraph why a straight-line projection is likely to be wrong in both directions, naming one reason it could understate the decline and one reason it could overstate it.

ELL supports

Pre-teach acre, acre-foot, drawdown, and pivot with a labeled sketch showing a circular field, a well, and the water level dropping over time. Provide sentence frames for item 8: "Output stayed high because ___," and "Population fell because ___." Allow students to answer item 4 with a labeled number line rather than a sentence.

Extensions

Have students find one county in their own state whose population peaked before 1980 and has fallen since, using published census tables the teacher provides, and write a paragraph comparing that county's story with the fictional Ryeland County. Students should name one factor that is shared and one that is not.