Worksheet Grade 5 Science
Glenray's Well Field in a Dry July: A Water Level Worksheet
Students subtract decimals to find the drawdown at four wells in a fictional town, then explain how a summer watering rule protects the gravel aquifer below.
Objectives
- Students will calculate drawdown at a well by subtracting the static level from the pumping level.
- Students will compare drawdown across four wells and explain what the largest value means.
- Students will explain how a town watering rule helps keep an aquifer from dropping too far.
Vocabulary
- Aquifer
- An aquifer is an underground layer of rock, sand, or gravel that holds water in the tiny spaces between its grains. Wells reach down into aquifers to bring water up to the surface.
- Drawdown
- Drawdown is how far the water level in a well drops when a pump pulls water out. The harder and longer you pump, the bigger the drawdown gets.
Also: well, static level, pumping level
Teacher overview
Glenray is a fictional town that draws all of its drinking water from four wells sunk into a gravel aquifer. Every Monday an operator measures each well twice: once with the pump off, which gives the static level, and once with the pump running, which gives the pumping level. The gap between those two numbers is the drawdown, and this worksheet has students find it four times with decimal subtraction and then read what the four values say about the aquifer in a dry month. A common student error here is subtracting in the wrong order because the numbers are depths below the ground, so the deeper reading is the larger number even though the water is lower; items 1 through 4 keep the order fixed to build the habit.
Student Worksheet
An operator in Glenray measured four wells on the same July morning. Each number tells how many feet below the ground the water sits. Drawdown is the pumping level minus the static level.
| Well | Static level, pump off | Pumping level, pump on |
|---|---|---|
| Well 1 | 18.5 feet | 26.2 feet |
| Well 2 | 19.0 feet | 29.4 feet |
| Well 3 | 21.3 feet | 30.8 feet |
| Well 4 | 20.6 feet | 24.9 feet |
- Find the drawdown at Well 1. Subtract 18.5 feet from 26.2 feet.
- Find the drawdown at Well 2. Subtract 19.0 feet from 29.4 feet.
- Find the drawdown at Well 3. Subtract 21.3 feet from 30.8 feet.
- Find the drawdown at Well 4. Subtract 20.6 feet from 24.9 feet.
- Which well has the largest drawdown?
- Well 2 has a drawdown of 10.4 feet. Well 4 has a drawdown of 4.3 feet. How much larger is Well 2's drawdown?
- In June the static level at Well 3 was 19.8 feet. In July it is 21.3 feet. How far did the static level drop?
- Glenray shuts a pump off if its pumping level passes 32 feet. Well 3 is at 30.8 feet. How many more feet can Well 3 drop before it reaches that line?
- The water in a well sits lower while the pump runs than when the pump is off. Explain why that happens.
- In July, Glenray asks families to water lawns on only two days each week. The town also posts the four well readings online every Monday. Explain how these two steps help protect the aquifer.
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: 7.7 feet. Subtract the static level from the pumping level: 26.2 - 18.5 = 7.7 feet of drawdown.
- Answer: 10.4 feet. Subtract the static level from the pumping level: 29.4 - 19.0 = 10.4 feet of drawdown.
- Answer: 9.5 feet. Subtract the static level from the pumping level: 30.8 - 21.3 = 9.5 feet of drawdown.
- Answer: 4.3 feet. Subtract the static level from the pumping level: 24.9 - 20.6 = 4.3 feet of drawdown.
- Answer: Well 2. Its drawdown of 10.4 feet is larger than 9.5 feet at Well 3, 7.7 feet at Well 1, and 4.3 feet at Well 4.
- Answer: 6.1 feet. Subtract the smaller drawdown from the larger one: 10.4 - 4.3 = 6.1 feet.
- Answer: 1.5 feet. Subtract the June reading from the July reading: 21.3 - 19.8 = 1.5 feet lower in July.
- Answer: 1.2 feet. Subtract the current pumping level from the shutoff depth: 32.0 - 30.8 = 1.2 feet of room left.
- Answer: The pump takes water out of the well faster than water can seep in from the gravel around it. That leaves the water in the well lower until the pump stops and the gravel refills the space. Accept any answer that says water is removed faster than the aquifer can replace it.
- Answer: Watering lawns on only two days each week means less water is pumped out in the driest month, so the levels have time to recover. Posting the readings lets people in town see the levels dropping and decide to save water before a well reaches its shutoff depth. Accept any answer that connects less pumping or shared information to protecting the aquifer.
Differentiation
Support
Give these students items 1 through 4 with the subtraction already written vertically and the decimal points aligned, so their work is the arithmetic rather than the setup. Provide a simple side-view sketch of one well showing the ground line, the static level, and the pumping level with the drawdown marked between them.
Extension
Ask these students to predict what Well 3's pumping level would reach if its static level dropped another 1.5 feet in August while its drawdown stayed at 9.5 feet, then decide whether the town would have to shut that pump off under the 32-foot rule and explain the reasoning in two sentences.
ELL supports
Pre-teach static, pumping, and drawdown with a clear jar of gravel and water and a turkey baster: the water line before the baster is used is the static level, and the lower line while a student draws water out with the baster is the pumping level. Allow items 9 and 10 to be answered with a labeled drawing plus a short phrase.
Extensions
Have students find whether their own community draws water from wells or from surface water, using a printed water quality report the teacher supplies, and write a short paragraph on what a town with wells would need to watch during a dry summer.