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Rainwater Harvesting worksheet

Grades 6–7 · CCSS 6.RP.A.3.d

Solve each problem and show your work. Round answers to 2 decimal places where needed.

1.
Problem 1.
- Units: Metric (m², mm, liters)
- Roof area that drains to the tank (measured flat, from above): 140 m²
- Rainfall over the period: 950 mm
- Rain from one large storm (for tank size): 29 mm
- Collection efficiency: 60%
Find: Water collected
Answer
2.
Problem 2.
- Units: US (ft², inches, gallons)
- Roof area that drains to the tank (measured flat, from above): 1,475 ft²
- Rainfall over the period: 30 in
- Rain from one large storm (for tank size): 1 in
- Collection efficiency: 90%
Find: Water collected
Answer
3.
Problem 3.
- Units: Metric (m², mm, liters)
- Roof area that drains to the tank (measured flat, from above): 170 m²
- Rainfall over the period: 740 mm
- Rain from one large storm (for tank size): 24 mm
- Collection efficiency: 80%
Find: Water collected
Answer
4.
Problem 4.
- Units: Metric (m², mm, liters)
- Roof area that drains to the tank (measured flat, from above): 140 m²
- Rainfall over the period: 1,300 mm
- Rain from one large storm (for tank size): 29 mm
- Collection efficiency: 100%
Find: Water collected
Answer
5.
Problem 5.
- Units: Metric (m², mm, liters)
- Roof area that drains to the tank (measured flat, from above): 140 m²
- Rainfall over the period: 850 mm
- Rain from one large storm (for tank size): 20 mm
- Collection efficiency: 70%
Find: Water collected
Answer
6.
Problem 6.
- Units: Metric (m², mm, liters)
- Roof area that drains to the tank (measured flat, from above): 100 m²
- Rainfall over the period: 775 mm
- Rain from one large storm (for tank size): 17 mm
- Collection efficiency: 85%
Find: Water collected
Answer
7.
Problem 7.
- Units: Metric (m², mm, liters)
- Roof area that drains to the tank (measured flat, from above): 140 m²
- Rainfall over the period: 1,380 mm
- Rain from one large storm (for tank size): 22 mm
- Collection efficiency: 85%
Find: Water collected
Answer
8.
Problem 8.
- Units: Metric (m², mm, liters)
- Roof area that drains to the tank (measured flat, from above): 158 m²
- Rainfall over the period: 775 mm
- Rain from one large storm (for tank size): 32 mm
- Collection efficiency: 80%
Find: Water collected
Answer
9.
Problem 9.
- Units: US (ft², inches, gallons)
- Roof area that drains to the tank (measured flat, from above): 1,500 ft²
- Rainfall over the period: 25 in
- Rain from one large storm (for tank size): 1 in
- Collection efficiency: 100%
Find: Water collected
Answer
10.
Problem 10.
- Units: US (ft², inches, gallons)
- Roof area that drains to the tank (measured flat, from above): 1,400 ft²
- Rainfall over the period: 38 in
- Rain from one large storm (for tank size): 1 in
- Collection efficiency: 95%
Find: Water collected
Answer

Answer key: Rainwater Harvesting worksheet

1. Water collected: 79,800 L
1. Water collected: multiply area × rainfall, since 1 mm on 1 m² is 1 liter. Then keep the 60% that reaches the tank
  $140 \times 950 \times 0.6$ $= 79,800 L$
2. Tank size: do the same with one large storm's rain, so the tank can hold it without overflowing
  $140 \times 29 \times 0.6$ $= 2,436 L$
2. Water collected: 24,826 gal
1. Find the gallons in 1 inch of rain on 1 square foot: that is 144 in³ of water, and a gallon is 231 in³
  $\frac{144}{231}$ $= 0.623377 gal per ft² per in$
2. Water collected: multiply area × rainfall × 0.6234 gallons, then keep the 90% that reaches the tank
  $1,475 \times 30 \times 0.623377 \times 0.9$ $= 24,825.974 gal$
3. Tank size: do the same with one large storm's rain, so the tank can hold it without overflowing
  $1,475 \times 1 \times 0.623377 \times 0.9$ $= 827.5325 gal$
3. Water collected: 100,640 L
1. Water collected: multiply area × rainfall, since 1 mm on 1 m² is 1 liter. Then keep the 80% that reaches the tank
  $170 \times 740 \times 0.8$ $= 100,640 L$
2. Tank size: do the same with one large storm's rain, so the tank can hold it without overflowing
  $170 \times 24 \times 0.8$ $= 3,264 L$
4. Water collected: 182,000 L
1. Water collected: multiply area × rainfall, since 1 mm on 1 m² is 1 liter. Then keep the 100% that reaches the tank
  $140 \times 1,300 \times 1$ $= 182,000 L$
2. Tank size: do the same with one large storm's rain, so the tank can hold it without overflowing
  $140 \times 29 \times 1$ $= 4,060 L$
5. Water collected: 83,300 L
1. Water collected: multiply area × rainfall, since 1 mm on 1 m² is 1 liter. Then keep the 70% that reaches the tank
  $140 \times 850 \times 0.7$ $= 83,300 L$
2. Tank size: do the same with one large storm's rain, so the tank can hold it without overflowing
  $140 \times 20 \times 0.7$ $= 1,960 L$
6. Water collected: 65,875 L
1. Water collected: multiply area × rainfall, since 1 mm on 1 m² is 1 liter. Then keep the 85% that reaches the tank
  $100 \times 775 \times 0.85$ $= 65,875 L$
2. Tank size: do the same with one large storm's rain, so the tank can hold it without overflowing
  $100 \times 17 \times 0.85$ $= 1,445 L$
7. Water collected: 164,220 L
1. Water collected: multiply area × rainfall, since 1 mm on 1 m² is 1 liter. Then keep the 85% that reaches the tank
  $140 \times 1,380 \times 0.85$ $= 164,220 L$
2. Tank size: do the same with one large storm's rain, so the tank can hold it without overflowing
  $140 \times 22 \times 0.85$ $= 2,618 L$
8. Water collected: 97,960 L
1. Water collected: multiply area × rainfall, since 1 mm on 1 m² is 1 liter. Then keep the 80% that reaches the tank
  $158 \times 775 \times 0.8$ $= 97,960 L$
2. Tank size: do the same with one large storm's rain, so the tank can hold it without overflowing
  $158 \times 32 \times 0.8$ $= 4,044.8 L$
9. Water collected: 23,377 gal
1. Find the gallons in 1 inch of rain on 1 square foot: that is 144 in³ of water, and a gallon is 231 in³
  $\frac{144}{231}$ $= 0.623377 gal per ft² per in$
2. Water collected: multiply area × rainfall × 0.6234 gallons, then keep the 100% that reaches the tank
  $1,500 \times 25 \times 0.623377 \times 1$ $= 23,376.6234 gal$
3. Tank size: do the same with one large storm's rain, so the tank can hold it without overflowing
  $1,500 \times 1 \times 0.623377 \times 1$ $= 935.0649 gal$
10. Water collected: 31,505 gal
1. Find the gallons in 1 inch of rain on 1 square foot: that is 144 in³ of water, and a gallon is 231 in³
  $\frac{144}{231}$ $= 0.623377 gal per ft² per in$
2. Water collected: multiply area × rainfall × 0.6234 gallons, then keep the 95% that reaches the tank
  $1,400 \times 38 \times 0.623377 \times 0.95$ $= 31,505.4545 gal$
3. Tank size: do the same with one large storm's rain, so the tank can hold it without overflowing
  $1,400 \times 1 \times 0.623377 \times 0.95$ $= 829.0909 gal$