Worksheet Grade 10 Science

Saddleback Farms: Comparing Flood and Drip Irrigation Water Use

A grade 10 worksheet where students compute crop water demand and compare flood and drip irrigation efficiency for a fictional farm weighing a system switch.

Grade: Grade 10
Subject: Science
Material: Worksheet
Time: 35 min
Prep: No prep
Materials: Calculator

Standards

HS-ESS3-4 NGSS

Evaluate or refine a technological solution that reduces impacts of human activities on natural systems.

How this material aligns: Items 9 and 10 have students evaluate drip irrigation as a technological solution that reduces the water Saddleback withdraws from the shared river and aquifer, weighing its installation cost against the reduced impact on those natural systems.

All materials for HS-ESS3-4 →

HSN-Q.A.1 Common Core Math

Use units as a way to understand problems and to guide the solution of multi-step problems; choose and interpret units consistently in formulas; choose and interpret the scale and the origin in graphs and data displays.

How this material aligns: Students carry inches, acres, acre-inches, and gallons consistently through the crop-demand and irrigation-efficiency calculations in items 1 through 7.

All materials for HSN-Q.A.1 →

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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 calculate a crop's monthly water demand from a daily evapotranspiration rate.
Students will compare the water applied under flood and drip irrigation and quantify the savings.

Vocabulary

Evapotranspiration: Evapotranspiration is the total amount of water that leaves the land and goes into the air, both from wet surfaces and from plants. Scientists combine evaporation and transpiration into one word.
Irrigation efficiency: The share of irrigation water that crops actually use compared with the amount taken from the river or well. Higher efficiency means less waste.
Drip irrigation: Watering plants through tubes that release water slowly, drop by drop, right at the roots. Very little water is wasted along the way.
Consumptive use: The share of water that is truly used up, by evaporating or being taken up by plants, so it cannot return to the river for others. The rest flows back and can be used again downstream.

Also: acre-inch

Teacher overview

Saddleback Farms is a fictional operation in a dry valley deciding whether to replace its old flood irrigation with a drip system. Flood irrigation soaks a whole field, and much of the water runs off or sinks below the roots. Drip irrigation delivers water slowly to each plant, so far less is wasted. This worksheet has students calculate how much water the crop actually needs, then compare how much each method must apply to deliver it. A common error to watch for is treating the crop's water need as the amount that must be pumped, when a method's efficiency means more water has to be applied than the crop uses.

Saddleback Farms: Comparing Flood and Drip Irrigation Water Use — Grade 10 Science

Name: ____________________________ Date: ______________

Student Worksheet

Saddleback Farms is a fictional farm, and all values below are given for one of its fields. Use these numbers and the conversion provided:

Field area: 50 acres.
Peak crop water use (evapotranspiration): 0.25 inches per day.
Flood irrigation efficiency: 60 percent (0.60 of the applied water reaches the roots).
Drip irrigation efficiency: 90 percent (0.90 of the applied water reaches the roots).
Conversion: 1 acre-inch = 27,154 gallons.

At 0.25 inches per day, how many inches of water does the crop use over a 30-day month? This is the crop's net water need.
Multiply the crop's monthly need (in inches) by the 50-acre area to get acre-inches, then convert to gallons using the conversion above.
With flood irrigation at 60 percent efficiency, the farm must apply more water than the crop uses. Find the gross water applied by dividing the net gallons from item 2 by 0.60.
With drip irrigation at 90 percent efficiency, find the gross water applied by dividing the net gallons from item 2 by 0.90.
How many gallons would Saddleback save in a month by switching from flood to drip? Subtract your drip answer from your flood answer.
Express the item 5 savings as a percentage reduction from the flood amount. Round to the nearest whole percent.
The valley limits each farm to 12,000,000 gallons of applied water per month. Which method keeps Saddleback within the limit? Support your answer with your item 3 and item 4 results.
Explain, in terms of where water is lost, why drip irrigation reaches a higher efficiency than flood irrigation.
A drip system is expensive to install. Describe how a farmer would weigh that upfront cost against the monthly water savings you calculated when deciding whether to switch.
Explain how Saddleback's choice between flood and drip would affect the shared river and aquifer that every farm in the valley draws from.

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: 7.5 inches. 0.25 inches per day times 30 days = 7.5 inches of water used over the month.
Answer: 10,182,750 gallons. 7.5 inches times 50 acres = 375 acre-inches; 375 times 27,154 gallons = 10,182,750 gallons.
Answer: 16,971,250 gallons. 10,182,750 gallons divided by 0.60 = 16,971,250 gallons applied under flood irrigation.
Answer: about 11,314,167 gallons. 10,182,750 gallons divided by 0.90 = 11,314,166.7, which rounds to about 11,314,167 gallons.
Answer: about 5,657,083 gallons. 16,971,250 minus 11,314,167 = 5,657,083 gallons saved in the month.
Answer: about 33%. 5,657,083 divided by 16,971,250, times 100 = 33.3 percent, which rounds to about 33 percent.
Answer: Drip only. Flood applies about 16,971,250 gallons, which is over the 12,000,000-gallon limit, while drip applies about 11,314,167 gallons, which stays under it.
Answer: Flood irrigation loses water to runoff, evaporation from the wet field surface, and deep percolation below the roots. Drip delivers water slowly right at each plant, so much less evaporates or drains away, which raises its efficiency.
Answer: Accept any reasoned response that compares the one-time installation cost against the recurring monthly savings, noting that the larger the water bill or the scarcer the water, the sooner the savings would pay back the cost of the system.
Answer: Because drip applies far less water for the same crop, choosing it would lower how much Saddleback withdraws from the shared river and aquifer, while sticking with flood would keep those withdrawals high. Some of the water flood irrigation "loses" returns to the river as runoff and to the aquifer as deep percolation, so the real gain for other users is smaller than the difference in applied water. Accept answers based on reduced withdrawals; give full credit to answers that also mention these return flows.

Differentiation

Support

Pre-compute the net gallons in item 2 and provide the two efficiency divisions set up as labeled expressions (net divided by 0.60 and net divided by 0.90) so students can focus on the comparison and the savings rather than the setup.

Extension

Have students calculate how many months of the 5,657,083-gallon savings it would take to repay a drip system that costs a set amount the teacher provides, and then determine what efficiency a third method would need to cut the water lost under flood irrigation in half.

ELL supports

Pair "evapotranspiration," "efficiency," and "acre-inch" with simple visuals (a plant releasing water vapor, a bucket with a leak, and a one-acre square one inch deep). Provide the efficiency step as an arrow rule ("net water divided by efficiency gives applied water") and allow items 8 through 10 to be answered with labeled sketches plus short phrases.