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The Dry Year in Cottonwood Basin: Farms, Wells and Sinking Land

Grade 8 argument practice: farm water records, home well depths and land sinking data show how growth and groundwater use affect a valley in a dry year.

Grade 8ScienceInteractive · Printable

Aligned toMS-ESS3-4

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What’s included

Single worksheet
Auto-graded online
1 NGSS standard
Printable answer key
10 questions
Classroom-ready

Details

Format: Interactive · Printable
Grade: Grade 8
Subject: Science
Question types: Fill in the blank, Multiple choice, Circle the answer, Short answer

About this worksheet

What students practice

Students compare groundwater pumping with aquifer refill to explain a falling water table.
Students read a histogram of well depths to find how many home wells go dry.
Students argue from data how growth in farmland and water use affects water and land in a valley.

How to use

Before reading, ask students where their own tap water comes from. Have pairs check each calculation, then write the argument in question 10 on their own.

Curriculum

NGSS standard covered

MS-ESS3-4

Argue how growth in human population and resource use affects Earth's systems.

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The Dry Year in Cottonwood Basin: Farms, Wells and Sinking Land

Use water records, a histogram of well depths and growth data to argue how people's water use changes a farming valley.

Part 1: A normal year and a dry year

Read the passage and Table 1, then answer questions 1–3.

When the Snow Did Not Come

1Esperanza Walcott lives in Cottonwood Basin, a wide farming valley whose vegetables, fruit and nuts are trucked to cities across the state. Her grandfather, Mr. Ignacio Walcott, grows tomatoes and almonds. Farms in the basin water their crops in two ways. Canals bring river water fed by melting snow from the mountains, and pumps lift groundwater from an aquifer, the layers of sand and gravel underground whose spaces hold water. The water table is the top of that underground water, measured as a depth below the ground.

2In the winter before 2021, the mountains got only about 40% of their usual snow. The river ran low, and the canals delivered much less water that year, so farmers pumped more groundwater to keep their crops alive. Ms. Dagny Fontaine, a hydrologist with the basin's water district, visited Esperanza's eighth grade class with the district's records. She explained that rain and water soaking in from the river refill the aquifer each year, but much less water soaks in during a dry year. Table 1 compares 2019, a normal year, with 2021.

3Many homes outside the towns get their drinking water from their own wells. A well goes dry when the water table falls below the bottom of the well. By the end of the 2021 summer, the water table under the town of Linden Flat had dropped to 50 m below the ground. Families whose wells failed had to haul drinking water in tanks or pay to have their wells drilled deeper, and a small wetland fed by springs at the edge of town dried up for the first time in decades. The graph shows the depths of all 60 home wells near Linden Flat.

4The district also measures the height of the land itself. Deep under the basin lie layers of clay mixed with the sand and gravel. When a lot of water is pumped out, the clay layers squeeze together, and the ground above them slowly sinks. Clay that has been squeezed this way does not take back as much water later. In 2021 a section of the main canal sank so much that it had to be raised and patched. Finally, Ms. Fontaine showed how the basin has grown since 1990 (Table 2).