Water for Schools
Menu

Lesson plan Grade 7 Health & Consumer Science

Sable Bend's Drought Ration: Ranking Household Water Uses

Students work out a fictional family's daily gallons under a drought limit, find the percent cut required, and decide which uses protect health and get cut last.

Objectives

  1. Students will calculate a household daily water allowance and the percent cut needed to reach it.
  2. Students will compare two showerhead flow rates and find the gallons and percent saved.
  3. Students will rank household water uses by how directly each one protects health.

Vocabulary

Drought
A long stretch of drier-than-normal weather that leaves too little water for people, farms, and nature. Droughts build slowly and can last for years.
Flow rate
Flow rate measures how much water moves past a point in a certain amount of time, like gallons per minute through a garden hose. Bigger pipes and stronger pushes give bigger flow rates.

Also: ration, percent decrease, hygiene

Teacher overview

When a drought forces a town to set a daily water allowance, a household has to decide what to give up, and several of those decisions affect health directly. This lesson puts students inside the fictional town of Sable Bend, where every household is asked to hold use to 45 gallons per person per day, well under the 80 to 100 gallons per person that Americans commonly use at home. Students calculate the family's allowance, the percent cut required, and the savings from a lower-flow showerhead, then rank four uses by how directly each protects health. The misconception to address directly is that cutting water use means washing less. Hygiene and drinking are the last uses a household should reduce, while outdoor watering, long showers, and running taps are the first.

Procedure

  • Hook (5 min): Ask students to list every way they used water before school this morning. Take five answers aloud, then ask which one they would give up first if the town told them to cut their household use in half.

  • Frame the scenario (8 min): Introduce the fictional Sable Bend drought order: 45 gallons per person per day for every household until the reservoir recovers. Explain that some uses protect health directly, such as drinking, handwashing, cooking, and flushing, while others are comfort or convenience. Write the phrase "cut last" on the board and tell students they will decide what belongs under it.

  • Worked example, teacher modeled (10 min): Work a different household on the board so students see the moves before they try their own. Suppose a 3-person household in Sable Bend used 60 gallons per person each day before the drought. Their old total was 180 gallons per day, and their new allowance is 3 times 45, which is 135 gallons per day. The cut is 45 gallons out of 180, and 45 divided by 180 is 0.25, which is a 25 percent cut. Do not let students copy this as an answer; it is a model, and their handout uses a different household.

  • Student handout (18 min): Students work items 1 through 11 with a partner and calculators, then answer item 12 on their own. Circulate and check that item 3 is set up as a change divided by the original amount rather than a difference alone, which is the most common error at this grade.

  • Ranking discussion (6 min): Groups post their answer to item 12 on chart paper. Run a quick thumbs up or thumbs down poll on the statement "shorter showers should be cut before handwashing." Before moving on, at least four out of five students should place handwashing and drinking above showers, and if fewer do, work one more example aloud about what happens to illness in a household that stops washing hands.

  • Exit ticket (3 min): Students hand in the handout with item 12 completed. Use those responses to decide whether the next class period opens with a review of percent decrease or with the outdoor-use extension.

Sable Bend's Drought Ration: Ranking Household Water Uses — Grade 7 Health & Consumer Science
Name: ____________________________ Date: ______________

Student Handout

The fictional town of Sable Bend is in a drought. The town has asked every household to hold water use to 45 gallons per person each day. The Ruthers family has 4 people. Their own records from last summer show that they used 90 gallons per person each day. Show your work for each item.

  1. Under the drought limit of 45 gallons per person each day, how many gallons per day may the whole 4-person Ruthers family use?

  2. Last summer the family used 90 gallons per person each day. How many gallons per day did the 4-person family use then?

  3. The family must go from 360 gallons per day down to 180 gallons per day. By what percent must they cut their total daily use?

  4. A standard showerhead flows at 2.5 gallons per minute. How many gallons does one 8-minute shower use?

  5. The family takes four 8-minute showers a day with that 2.5 gallon-per-minute showerhead. How many gallons per day do those four showers use?

  6. A water-saving showerhead uses 2.0 gallons per minute. How many gallons would those same four 8-minute showers use with the water-saving showerhead?

  7. How many gallons per day does the family save by switching from the 2.5 gallon-per-minute showerhead to the 2.0 gallon-per-minute showerhead for those four showers?

  8. Shower use drops from 80 gallons per day to 64 gallons per day after the switch. By what percent did the family's shower use drop?

  9. With the new showerhead the family uses 64 gallons for showers, 42 gallons for toilet flushing, 20 gallons for handwashing and cleaning, and 12 gallons for drinking and cooking. How many gallons per day do those four uses total?

  10. The family's daily limit is 180 gallons. After the 138 gallons in item 9, how many gallons are left for everything else, such as laundry and outdoor watering?

  11. The family wants to save 10 more gallons a day by taking shorter showers. With the 2.0 gallon-per-minute showerhead, how many total minutes of shower time must they cut?

  12. Of these four uses, which two protect health most and should be cut last: showers, toilet flushing, handwashing and cleaning, or drinking and cooking? Explain your choice in one sentence.

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: 180 gallons.
    45 gallons per person times 4 people equals 180 gallons per day.

  2. Answer: 360 gallons.
    90 gallons per person times 4 people equals 360 gallons per day.

  3. Answer: 50 percent.
    The cut is 360 minus 180, which is 180 gallons. Then 180 divided by 360 equals 0.5, or 50 percent.

  4. Answer: 20 gallons.
    2.5 gallons per minute times 8 minutes equals 20 gallons.

  5. Answer: 80 gallons.
    20 gallons per shower times 4 showers equals 80 gallons per day.

  6. Answer: 64 gallons.
    2.0 gallons per minute times 8 minutes equals 16 gallons per shower, and 16 times 4 showers equals 64 gallons per day.

  7. Answer: 16 gallons.
    80 gallons minus 64 gallons equals 16 gallons saved per day.

  8. Answer: 20 percent.
    The drop is 80 minus 64, which is 16 gallons. Then 16 divided by 80 equals 0.2, or 20 percent.

  9. Answer: 138 gallons.
    64 plus 42 plus 20 plus 12 equals 138 gallons per day.

  10. Answer: 42 gallons.
    180 gallons minus 138 gallons equals 42 gallons left for everything else.

  11. Answer: 5 minutes.
    10 gallons divided by 2.0 gallons per minute equals 5 minutes of shower time to cut.

  12. Answer: Handwashing and cleaning, and drinking and cooking. These two protect health most directly, because drinking water prevents dehydration and handwashing stops the spread of illness, while shower length and flushing can be reduced without the same risk. Accept toilet flushing in place of one of them only if the student ties it to sanitation and explains why a household cannot stop flushing entirely.

Differentiation

Support

Give these students a version of the handout with items 1, 2, 4, and 5 already set up as equations that need only the arithmetic completed, and provide a percent-change reminder card reading "change divided by original, then times 100." Allow them to stop after item 9 and go straight to item 12.

Extension

Ask students to add outdoor watering to the family's plan using the 42 gallons left over from item 10, and to decide how many days a week a small vegetable garden could be watered at 15 gallons per watering without breaking the daily limit. Have them explain why a food garden might rank differently than a lawn.

ELL supports

Pre-teach "drought," "allowance," "flow rate," and "hygiene" with a picture card for each, and provide a labeled diagram of a showerhead with the two flow rates. Give a sentence frame for item 12: "The family should cut ___ last because ___."

Extensions

Students can compare the Sable Bend limit against their own household's water bill, which usually reports gallons or cubic feet used per month, and convert that figure to gallons per person per day. A follow-up discussion can look at how a town enforces a limit fairly when households differ in size, which is the same reasoning students used when they divided a household total by the number of people.