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Debate kit Grade 6 Science

Capping the Pumps Over the Tanmoor Flats Aquifer

A grade 6 science debate on whether a fictional district should limit yearly pumping to what an aquifer gains back, with two-sided well and recharge evidence.

Objectives

  1. Students will use well-level and recharge records to argue about a limit on groundwater pumping.
  2. Students will explain how pumping more than an aquifer gains back changes the water stored underground.
  3. Students will rebut an opposing claim by naming the record that weakens it.

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.
Recharge
Recharge is water soaking down through the ground to refill an aquifer, the way rain refills an underground sponge. Aquifers stay healthy only if recharge keeps up with pumping.
Water table
The water table is the underground level below which the ground is completely soaked with water. Dig a hole deeper than the water table and it will start filling with water.
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: subsidence, index well

Teacher overview

This debate runs as a groundwater district hearing across two class periods. Two teams of five argue over whether a fictional district should limit yearly pumping to the amount of water the aquifer gains back, a moderator keeps time, and the rest of the class serves as the district board and votes. The question is genuinely open, because the records show the water table falling while the estimate of how much water soaks back in each year carries real uncertainty. The misconception worth naming before students read the evidence is the picture of an aquifer as an underground lake or a buried river, with water levels springing back as soon as pumping stops. The water in this aquifer sits in the spaces between grains of sand and gravel and refills slowly from above, and where the ground has settled the lost storage does not come back at all. Students who hold the underground lake picture will treat the decline as easy to reverse.

Capping the Pumps Over the Tanmoor Flats Aquifer — Grade 6 Science
Name: ____________________________ Date: ______________

Resolution & Background

Resolution: "The Ravelsby Groundwater District should cap yearly pumping from the Tanmoor Flats aquifer at the amount of water the aquifer gains back each year."

Ravelsby is a fictional district on the Tanmoor Flats. Everything here about Ravelsby and Tanmoor Flats is fictional and was written for this debate.

Under the Flats lies a bed of sand and gravel left behind by an old river. Rain and snowmelt soak down into that bed and fill the spaces between the grains. Water sitting in those spaces is groundwater, and the bed that holds it is an aquifer. Recharge is the water that soaks in each year. Withdrawal is the water the pumps take out.

About 300 farms pump from the aquifer. So do the town of Ravelsby and a fruit packing plant. Water is measured here in acre-feet. One acre-foot covers an acre of ground one foot deep.

The district measures the depth to water in an index well each spring. It also runs a gauge on Corwood Brook, a small stream the aquifer feeds in dry months. The board must decide whether to set a hard cap, and the science is part of the argument on both sides.

Roles. Five students argue for the cap. Five argue against it. One student moderates and keeps time. Everyone else serves as the district board, writes questions on index cards, and votes.

Format. Each team gives a four-minute opening. Teams take six minutes to prepare. Each team gives a three-minute rebuttal and a two-minute closing. The board asks four questions from the cards, then votes. Each team turns in its written opening and its rebuttal notes.

Evidence File

Every record below is a fictional Ravelsby record written for this debate.

Case for the cap

  1. Depth to water in the index well has grown by 22 feet over the past 12 years. The level fell in wet years as well as dry ones, so rainfall alone does not explain it. (Source: a fictional district index well log.)
  2. The district hydrologist estimates that about 6,000 acre-feet soak into the aquifer in an average year. Meters recorded about 9,000 acre-feet pumped last year. Taking out more than goes in draws down the water stored underground. (Source: a fictional district water budget.)
  3. Corwood Brook ran dry for 30 days last August. The gauge record shows the brook never went dry in its first 20 years of measurement. In dry months the brook is fed by groundwater, so a falling water table shows up in the stream. (Source: a fictional district gauge record.)
  4. Fourteen shallow household wells have been deepened in the past five years because they stopped reaching water. Those families paid for the work themselves. (Source: a fictional county well permit file.)
  5. A survey benchmark near the district office has settled about 9 inches. When water leaves the clay layers, the ground packs down and those spaces close for good, so that part of the aquifer's storage cannot be refilled. (Source: a fictional survey record.)

Case against the cap

  1. A cap set at recharge would cut pumping by about one-third in the first year. A fictional farm survey reports that orchards cannot be cut back that fast, and trees planted 20 years ago would be lost rather than simply watered less. (Source: a fictional farm survey.)
  2. Recharge is an estimate, not a measurement. The same hydrologist's report gives a range of 5,000 to 7,500 acre-feet and notes that wet decades recharge more than dry ones. Writing one number into a rule hides that range. (Source: a fictional district water budget.)
  3. Two changes could save water without a cap. Converting furrow rows to drip lines and lining the main canal would save an estimated 1,800 acre-feet a year. (Source: a fictional irrigation district estimate.)
  4. Winter flood flows now leave the Flats unused. A fictional pilot spread one winter's flood water across a sandy field and put about 400 acre-feet underground in a single season. Adding recharge is another way to close the gap. (Source: a fictional recharge pilot report.)
  5. A meter audit shows that six large users pump more than half the total. A cap spread evenly across everyone would cut a small family orchard as hard as the largest pumper. (Source: a fictional district meter audit.)
  6. The index well sits about 200 feet from the district's largest pump. A monitoring review found that wells farther out dropped far less over the same 12 years, so the 22-foot figure describes one spot rather than the whole aquifer. (Source: a fictional monitoring review.)

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

Rubric
Criterion Emerging Developing Proficient Advanced
Use of evidence States a position with no evidence from the file Names one record but does not say what it shows Names at least two records and explains what each shows about the aquifer Names several records, explains each, and says which one carries the most weight and why
Reasoning about the aquifer Treats groundwater as an underground lake that refills at once Mentions recharge or withdrawal without connecting them Connects the gap between withdrawal and recharge to a falling water table or a dry brook Traces the gap through two or more effects, such as the brook and the settled benchmark, and notes what the records cannot settle
Rebuttal Does not respond to the other team Responds in general terms without naming a record Answers a specific opposing point using a named measurement Answers more than one opposing point and explains why the team's own evidence is stronger
Delivery and organization Hard to follow; no clear order Has an order, but transitions are unclear Follows a clear claim, evidence, and conclusion structure within the time limit Clear, well paced, and responsive to board questions as well as to the opening arguments

Differentiation

Support

Cut the evidence file down for these students to the two records that carry their side, enlarged, with the acre-foot figures underlined. Provide a simple cross section of the fictional aquifer showing rain soaking in, a pump drawing out, and the brook at the surface, and have them mark the arrows before they speak. Offer rebuttal frames such as "The other team said ___, but the district record shows ___." A student who prefers to read a prepared opening aloud may do so.

Extension

Ask a pair to act as the district hydrologist rather than debaters. They answer board questions about what the records can and cannot show, and they must flag any moment a speaker treats an estimate as a measurement. A second option is to draft a cap that phases in over five years and explain, using the fictional records, which evidence supports each step.

ELL supports

Pre-teach "aquifer," "recharge," "water table," "acre-foot," and "settling" with a labeled cross section drawing and a clear jar of gravel that students can pour water into and pump water out of. Provide a bilingual glossary card. Allow students to speak from a written script, and give extra preparation time before the rebuttal round. Accept a labeled drawing as part of a closing statement.

Extensions

Have students find out whether their own state requires a permit to drill a well, and report what the permit asks the driller to record. A second option is to design a monitoring plan for the fictional district: name three places to measure, say what instrument each needs, and explain what result would tell the board that a cap was working.