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Worksheet Grade 11 Health & Consumer Science

The Water Footprint of a Week's Meals: Beef and Wheat

A grade 11 consumer-science worksheet where students estimate the water footprint of a fictional week's menu using published beef and wheat water-use figures.

Objectives

  1. Students will estimate the water footprint of foods using gallons-per-pound figures.
  2. Students will write and evaluate an equation for a menu's total water footprint.
  3. Students will compare the water saved by a food swap to other conservation choices.

Vocabulary

Water footprint
All the water it takes to make the things we use and eat, counting water used far away. A hamburger's water footprint includes the water that grew the cattle's feed.

Also: gallons per pound, food swap

Teacher overview

Most of the water a person uses never comes out of a tap; it is used to grow food. In this worksheet students estimate the water footprint of a fictional week's dinners for a student named Priya, using the commonly cited figures that a pound of beef takes roughly 1,800 gallons of water to produce and a pound of wheat takes roughly 220 gallons. Students total the footprint, compare a food swap to a shorter shower, and connect the numbers to the fact that agriculture accounts for roughly 70% of the fresh water withdrawn worldwide.

The Water Footprint of a Week's Meals: Beef and Wheat — Grade 11 Health & Consumer Science
Name: ____________________________ Date: ______________

Student Worksheet

Producing a pound of beef takes roughly 1,800 gallons of water; a pound of wheat (used as bread and pasta) takes roughly 220 gallons. Most of the beef figure is rainwater that falls on the pasture and feed crops cattle eat, rather than water pumped from rivers or wells. Use these two figures for the fictional week of dinners planned by a student named Priya.

  1. Priya's household eats 3 pounds of beef in the week. Using 1,800 gallons per pound, how many gallons of water does that beef represent?
  2. The household uses 4 pounds of wheat foods in the week. Using 220 gallons per pound, how many gallons does that wheat represent?
  3. What is the combined water footprint of the beef and the wheat for the week?
  4. How many times larger is beef's water footprint than wheat's, per pound? Round to the nearest tenth.
  5. Priya swaps 1 pound of beef for 1 pound of wheat food. How many gallons of water does that single swap save?
  6. Write an equation for the total water footprint W, in gallons, of b pounds of beef and w pounds of wheat in a week.
  7. Use your equation to find W for 2 pounds of beef and 5 pounds of wheat.
  8. Priya wants the week's beef-and-wheat footprint at or below 4,000 gallons while keeping wheat at 5 pounds. Write and solve an inequality for the greatest whole number of pounds of beef b she can use.
  9. Agriculture accounts for roughly 70% of the fresh water people withdraw worldwide. In two or three sentences, explain how a household's food choices connect to that large agricultural share.
  10. Priya's friend says cutting a 10-minute shower saves more water than changing one meal. A standard showerhead flows at 2.5 gallons per minute. How many gallons does a 10-minute shower use, and how does that compare to the gallons saved by the one-pound beef-for-wheat swap in item 5?

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: 5,400 gallons. Three pounds of beef at 1,800 gallons per pound is 3 times 1,800, or 5,400 gallons.
  2. Answer: 880 gallons. Four pounds of wheat at 220 gallons per pound is 4 times 220, or 880 gallons.
  3. Answer: 6,280 gallons. The beef's 5,400 gallons plus the wheat's 880 gallons is 6,280 gallons.
  4. Answer: About 8.2 times. 1,800 gallons divided by 220 gallons is about 8.18, so beef's footprint per pound is about 8.2 times wheat's.
  5. Answer: 1,580 gallons. One pound of beef is 1,800 gallons and one pound of wheat is 220 gallons, so the swap saves 1,800 minus 220, or 1,580 gallons.
  6. Answer: W = 1,800b + 220w. Each pound of beef adds 1,800 gallons and each pound of wheat adds 220 gallons.
  7. Answer: 4,700 gallons. W = 1,800 times 2 plus 220 times 5, which is 3,600 plus 1,100, or 4,700 gallons.
  8. Answer: 1 pound. The inequality is 1,800b + 1,100 ≤ 4,000; subtracting 1,100 gives 1,800b ≤ 2,900, so b ≤ 1.61, and the greatest whole number is 1 pound.
  9. Answer: Much of the world's food is grown on irrigated land, and the water pumped from rivers and wells for those crops is what makes up agriculture's roughly 70% share of withdrawn fresh water. Household demand for food helps drive that irrigation, so everyday menu choices add up across many households. The rest of a food's footprint is rain that falls on fields and pasture, which is not counted as a withdrawal.
  10. Answer: 25 gallons; the meal swap saves far more. A 10-minute shower at 2.5 gallons per minute uses 25 gallons, while swapping one pound of beef for wheat saves 1,580 gallons, so the single food swap saves much more water than one shower by this measure. Most of the beef figure is rainwater used by pasture and feed crops, however, so the two savings are not the same kind of water.

Differentiation

Support

Provide items 1 and 2 with the multiplication set up (3 times 1,800 and 4 times 220) and a filled example of the equation in item 6 using different pound amounts. Allow a calculator throughout and accept the equation written with the numbers in either order.

Extension

Ask students to plan a revised week that keeps the beef-and-wheat footprint at or below 3,000 gallons, choosing whole-pound amounts of each food, and to show the equation and total that prove the menu meets the limit.

ELL supports

Pre-teach "water footprint," "per pound," and "swap" with a simple bar picture showing one long bar for beef and a short bar for wheat. Provide a sentence frame for items 9 and 10, such as "The choice that saves more water is ___ because ___."