Worksheet Grade 4 Science

Reading the Torbeck Reservoir Depth Log in a Dry Month

A grade 4 science worksheet using a fictional reservoir's five weekly depth readings to find drops in inches, convert to feet, and explain where the missing water went.

Grade: Grade 4
Subject: Science
Material: Worksheet
Time: 35 min
Prep: No prep
Materials: None

Standards

4.MD.A.1 Common Core Math

Know relative sizes of measurement units within one system of units including km, m, cm; kg, g; lb, oz; l, ml; hr, min, sec. Within a single system of measurement, express measurements in a larger unit in terms of a smaller unit. Record measurement equivalents in a two-column table.

How this material aligns: Item 7 applies the relative size of units within the customary system, using the twelve inches in a foot to restate the Week 1 reservoir depth.

All materials for 4.MD.A.1 →

4.MD.A.2 Common Core Math

Use the four operations to solve word problems involving distances, intervals of time, liquid volumes, masses of objects, and money, including problems involving simple fractions or decimals, and problems that require expressing measurements given in a larger unit in terms of a smaller unit.

How this material aligns: Items 1 through 3 subtract depths from the weekly log, and items 8 and 9 multiply inches lost by gallons per inch, so both sets are measurement word problems in inches and gallons.

All materials for 4.MD.A.2 →

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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 find weekly and total drops in reservoir depth by subtracting values from a data log.
Students will convert a depth given in inches into feet.
Students will explain that evaporation and daily water use both lower a reservoir when no rain falls.

Vocabulary

Reservoir: A human-made lake, usually created by a dam, that stores water for later. Reservoirs supply cities and farms and help control floods.
Evaporation: Evaporation happens when liquid water, often warmed by the sun, turns into an invisible gas called water vapor that rises into the air. It is how water leaves oceans, lakes, and puddles.
Water vapor: Water vapor is water in the form of an invisible gas mixed into the air. There is always some water vapor around you, even when the sky is completely clear.

Also: depth, pattern

Teacher overview

Torbeck Reservoir is a fictional lake held back by a small dam above the town of Torbeck, and the crew there measures the water depth beside the dam every Monday. During one rainless month the readings fell every week, and the size of the weekly fall kept growing as the summer heated up. This worksheet hands students that five-week log and asks them to find the weekly drops, the total drop, and the gallons behind those inches, then to explain where water goes when no rain returns it. The last two items give students a place to name evaporation and daily household use as the two paths water took out of the reservoir.

Reading the Torbeck Reservoir Depth Log in a Dry Month — Grade 4 Science

Name: ____________________________ Date: ______________

Student Worksheet

Torbeck Reservoir is a lake held back by a small dam. It supplies the drinking water for the town of Torbeck, and the crew there pumps water to homes every day. Use this depth log for every item. The crew measured the water beside the dam each Monday. No rain fell all month.

Reading	Water depth (inches)
Week 1	96
Week 2	90
Week 3	83
Week 4	75
Week 5	66

How many inches did the water drop from Week 1 to Week 2?
How many inches did the water drop from Week 4 to Week 5?
How many inches did the water drop in all, from Week 1 to Week 5?
Find the drop for each week. Look at the four drops in order. What pattern do you see?
Suppose the pattern keeps going. How many inches would the water drop from Week 5 to Week 6?
Use your answer from item 5. What depth would the log show in Week 6?
The Week 1 depth was 96 inches. How many feet is that?
Each inch of depth in this lake holds 80,000 gallons. The water fell 6 inches in the first week. How many gallons of water left the lake that week?
The water fell 9 inches in the last week. How many gallons of water left the lake that week?
No rain fell all month. Explain why the water still went down every week.
Some of the missing water rose into the air. Explain what happens to that water next.

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: 6 inches.
Subtract the two readings: 96 - 90 = 6 inches.
Answer: 9 inches.
Subtract the two readings: 75 - 66 = 9 inches.
Answer: 30 inches.
Subtract the last reading from the first: 96 - 66 = 30 inches. Students may also add the four weekly drops, since 6 + 7 + 8 + 9 = 30.
Answer: Each drop is 1 inch larger than the one before it.
The weekly drops are 6, 7, 8, and 9 inches, so each week loses one more inch than the week before.
Answer: 10 inches.
The pattern adds one inch each week, and 9 + 1 = 10 inches.
Answer: 56 inches.
Start from the Week 5 depth and take off the predicted drop: 66 - 10 = 56 inches.
Answer: 8 feet.
There are 12 inches in one foot, and 96 divided by 12 equals 8 feet.
Answer: 480,000 gallons.
Multiply inches by gallons per inch: 6 x 80,000 = 480,000 gallons.
Answer: 720,000 gallons.
Multiply inches by gallons per inch: 9 x 80,000 = 720,000 gallons.
Answer: Water left the lake even though none came in.
A full answer names at least one path out. The town kept pumping water to homes all month, and warm air kept lifting water off the surface, so the level fell every week with nothing added to replace it.
Answer: It becomes water vapor and can later fall again as rain.
Accept any answer stating that the water rises into the air as invisible vapor, cools and forms clouds, and returns to the ground as rain or snow somewhere else.

Differentiation

Support

Give these students a printed number line marked from 60 to 100 in ones so they can hop between the weekly readings instead of subtracting on paper. Work item 1 together as a class, and provide a printed ruler showing 12 inches next to a one-foot mark for item 7.

Extension

Ask students to extend the log through Week 8 using the same pattern, then explain in writing why a real reservoir cannot keep losing more inches every week forever. Students can also calculate the gallons behind the full 30-inch drop and describe how many weeks of Week 1 losses that equals.

ELL supports

Pre-teach reservoir, depth, and evaporation with a labeled side-view sketch of a lake behind a dam, with an arrow going up for vapor and an arrow going sideways for water piped to homes. Provide sentence frames for items 10 and 11: "The water went down because ___" and "The water in the air turns into ___."