Lesson plan Grade 3 Engineering & Design

Quarry Ridge Model Dam: Building a Reservoir on Slate Creek

A grade 3 engineering lesson: students fair-test dam materials to hold back model Slate Creek, then solve liquid-volume word problems about their fictional reservoir.

Grade: Grade 3
Subject: Engineering & Design
Material: Lesson plan
Time: 60 min
Prep: Moderate prep
Materials: Shallow tray or plastic tub (1 per group), Modeling clay, Small rocks or pebbles, Craft sticks, Measuring cup marked in liters or milliliters, Water (about 2 liters per group), Ruler, Paper towels

Standards

3-5-ETS1-3 NGSS

Plan and carry out fair tests in which variables are controlled and failure points are considered to identify aspects of a model or prototype that can be improved.

How this material aligns: Groups run a fair test that changes only the dam-wall material while keeping the tray, slope, and water amount the same, the controlled-variable testing this standard requires.

All materials for 3-5-ETS1-3 →

3.MD.A.2 Common Core Math

Measure and estimate liquid volumes and masses of objects using standard units of grams (g), kilograms (kg), and liters (l). Add, subtract, multiply, or divide to solve one-step word problems involving masses or volumes that are given in the same units, e.g., by using drawings (such as a beaker with a measurement scale) to represent the problem.

How this material aligns: Handout problems 1 through 4 add, subtract, and multiply liters of water held in and lost from the model reservoir, the one-step liquid-volume word problems in standard units this standard names.

All materials for 3.MD.A.2 →

3.OA.D.8 Common Core Math

Solve two-step word problems using the four operations. Represent these problems using equations with a letter standing for the unknown quantity. Assess the reasonableness of answers using mental computation and estimation strategies including rounding.

How this material aligns: Handout problem 5 combines multiplication and subtraction into a single two-step reservoir question, and problem 6 asks students to judge a total against an estimate before computing it, the two steps and the reasonableness check this standard names.

All materials for 3.OA.D.8 →

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This material is in the public domain (CC0) and may be copied, edited, and shared freely, without attribution. Updated 2026-07-23.

Objectives

Students will run a fair test that changes one dam material to find which best holds back water.
Students will add, subtract, and multiply liters to solve reservoir word problems.
Students will solve a two-step reservoir problem and check the answer with an estimate.

Vocabulary

Dam: A strong wall built across a river to hold back water. Dams store water for people and farms, help prevent floods, and can make electricity.
Reservoir: A human-made lake, usually created by a dam, that stores water for later. Reservoirs supply cities and farms and help control floods.

Also: fair test, leak, liter

Teacher overview

Quarry Ridge is a fictional town that wants to hold back part of Slate Creek to make a reservoir, a pond of stored water it can use in dry weather. In this lesson, groups build a small model dam across a tray, run a fair test to see which wall material leaks least, and then work reservoir word problems that use the liters their model could hold. The math is grade 3 liquid-volume work, so a common misconception to watch for is students adding a leak amount to the stored water instead of subtracting it; the handout is built to surface and correct that mistake in problem 4.

Procedure

Hook (5 min): Pour a thin stream of water down a tilted empty tray so students see the "creek" run straight off the end. Ask, "How could we trap some of this water to save for a dry day?" Introduce the words dam and reservoir.

Define the problem and plan the fair test (10 min): With the class, agree on the fair-test rule: every group uses the same tray, the same tilt, and the same amount of water, and changes only the wall material. Each group picks one wall to test first, either packed clay or stacked rocks, so the test compares materials fairly.

Build the dam (15 min): Groups build a wall across the middle of the tray with their chosen material, using craft sticks for support. The goal is a wall that holds a small reservoir behind it without washing away.

Run the fair test (10 min): Each group slowly pours the same measured amount of water above the wall and watches for leaks. Groups note whether the reservoir holds or the wall lets water through, then, if time allows, rebuild with the other material and pour again to compare.

Reservoir math (15 min): Hand out the Student Handout. Students imagine their model reservoir holds up to 12 liters and solve the numbered problems about filling it, losing water to leaks, and drawing water for a garden. Circulate and prompt estimation before exact answers.

Debrief and exit (5 min): Groups share which wall material leaked less and why. For a formative check, collect the handout and scan problem 4: any student who added instead of subtracting needs a quick reteach of "a leak takes water away."

Quarry Ridge Model Dam: Building a Reservoir on Slate Creek — Grade 3 Engineering & Design

Name: ____________________________ Date: ______________

Student Handout

Quarry Ridge's model reservoir can hold up to 12 liters of water. Solve each problem and show your work.

The reservoir starts empty. The class pours in 5 liters, then 4 more liters. How many liters are in the reservoir now?
The reservoir can hold 12 liters at most. After problem 1, how many more liters can still fit?
The dam leaks 2 liters each hour. How many liters leak out in 3 hours?
The reservoir held 9 liters. After the 3 hours of leaks from problem 3, how many liters are left?
Each day the town draws 4 liters from a full 12-liter reservoir to water a garden, for 2 days. How many liters are left after the two days?
The class pours in 5 liters, 4 liters, and 2 liters. First estimate whether the total is closer to 10 or 15 liters, then find the exact total.

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

Answer Key

Answer: 9 liters. 5 liters + 4 liters = 9 liters poured in.
Answer: 3 liters. The reservoir holds 12 liters and already has 9, so 12 − 9 = 3 more liters can fit.
Answer: 6 liters. A 2-liter leak each hour for 3 hours is 2 × 3 = 6 liters.
Answer: 3 liters. The leak takes water away, so 9 − 6 = 3 liters are left. A student who wrote 15 added instead of subtracted.
Answer: 4 liters. Two days of drawing 4 liters is 4 × 2 = 8 liters used; 12 − 8 = 4 liters left.
Answer: 11 liters. Estimate: 5 + 4 + 2 is close to 10. Exact: 5 + 4 + 2 = 11 liters, which is closer to 10 than to 15.

Differentiation

Support

Give these students a number line from 0 to 12 to model each pour and each leak as a jump forward or back. Provide the reservoir drawn as a jug with liter lines already marked, so they can shade the water level for problems 1 and 2 before writing.

Extension

Ask these students to design a reservoir that must still have at least 5 liters after two days of garden watering and three hours of leaks, and to explain how many liters it must start with. Have them write their own two-step problem for a partner.

ELL supports

Pre-teach "dam," "reservoir," "leak," and "liter" with a labeled picture of a real dam holding back a lake. Provide the sentence frame "The reservoir has ___ liters because ___." Let students use the marked jug drawing to show answers instead of full sentences.

Extensions

Have the class compare their model to a photo of a real earthen dam and point out the same packed material they used. Groups that finish early can test whether a wider wall base leaks less than a narrow one, keeping every other part of the test the same.