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Worksheet Grade 12 Social Studies & Civics

Governing the Aldous Basin Aquifer: A Common-Pool Resource Worksheet

A grade 12 economics worksheet where students confront a fictional aquifer's overdraft and compare rules for sharing a depleting common-pool groundwater resource.

Objectives

  1. Students will calculate an aquifer's annual overdraft from recharge and pumping figures.
  2. Students will compare allocation rules for a shared groundwater resource.
  3. Students will explain the reciprocal effects of overpumping on the physical basin.

Vocabulary

Recharge
Recharge is water soaking down through the ground to refill an aquifer, the way rain refills an underground sponge. Aquifers stay healthy only if recharge keeps up with pumping.

Also: common-pool resource, overdraft, groundwater management district, allocation, subsidence, tragedy of the commons

Teacher overview

Groundwater is a hard resource to govern because no fence marks a person's share of an aquifer, yet every well draws from the same pool. When farmers each pump as much as they need, the water table can fall faster than rain refills it, and the whole basin loses. This worksheet gives students the water budget of the fictional Aldous Basin, where four farms are pumping more than the aquifer can replace. Students calculate the overdraft, weigh three different rules for dividing a capped supply, and judge which rule best balances fairness against the goal of saving the aquifer.

Governing the Aldous Basin Aquifer: A Common-Pool Resource Worksheet — Grade 12 Social Studies & Civics
Name: ____________________________ Date: ______________

Student Worksheet

The fictional Aldous Basin aquifer is refilled by rain and snowmelt at a rate of about 12,000 acre-feet per year. Four farms in Verdant Valley pump from it. Together they now withdraw 18,000 acre-feet per year. One large farm, Verdant Ridge, pumps 6,000 acre-feet by itself; the other three each pump 4,000 acre-feet. Use these figures for all items.

  1. Define a "common-pool resource" and explain why the Aldous Basin aquifer is one.
  2. The aquifer recharges 12,000 acre-feet per year, and the farms pump 18,000 acre-feet per year. Calculate the aquifer's annual overdraft.
  3. Explain how the "tragedy of the commons" applies here, using the fact that each farm keeps the full benefit of its own pumping but shares the falling water table with everyone.
  4. Overpumping lowers the water table. Describe one reciprocal effect this physical change could have on the farms or the land, and explain the link.
  5. A new groundwater management district caps total pumping at the 12,000-acre-foot recharge rate. By what percent must the farms' combined pumping fall to meet the cap?
  6. Suppose the district splits the 12,000-acre-foot cap equally among the four farms. How many acre-feet would each farm receive, and how does that compare with what Verdant Ridge pumps now?
  7. Instead, the district could allocate by historical use, giving each farm the same share of the cap as its share of current pumping. Explain who gains and who loses compared with the equal split.
  8. The district could also let farms buy and sell their allocations. Explain one incentive this market would create and one concern it raises.
  9. Evaluate one intended outcome and one unintended outcome of capping total pumping at the recharge rate.
  10. Recommend one allocation rule for the Aldous Basin and justify it using both fairness and the goal of protecting 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
  1. Answer: A common-pool resource is one that is hard to fence off but can be used up. The aquifer qualifies because any farm with a well can draw from it, and water one farm pumps is no longer available to the others.
  2. Answer: 6,000 acre-feet per year. 18,000 acre-feet pumped minus 12,000 acre-feet of recharge equals a 6,000-acre-foot overdraft each year.
  3. Answer: Each farm gets the full value of the water it pumps but bears only a fraction of the shared cost of the falling water table, so every farm has a reason to keep pumping even though the combined result drains the basin.
  4. Answer: Any reasonable reciprocal effect, such as wells having to be drilled deeper and pumping costing more as the table drops, neighboring wells going dry, or the land subsiding and cracking as the emptied pore space compacts.
  5. Answer: 33 percent. The farms must cut from 18,000 to 12,000 acre-feet, a reduction of 6,000, and 6,000 divided by 18,000 is about one-third, or 33 percent.
  6. Answer: 3,000 acre-feet each. 12,000 divided by four farms is 3,000. Verdant Ridge, which now pumps 6,000, would lose half its water, a much larger cut than the smaller farms face.
  7. Answer: Historical allocation gives Verdant Ridge the largest share because it pumps the most now, so it gains relative to the equal split, while the three smaller farms receive less than they would under an equal division.
  8. Answer: A market creates an incentive for the most efficient users to buy water and for others to sell rather than waste it; a concern is that a wealthy farm could buy up most of the allocations and concentrate control of the basin.
  9. Answer: Answers vary. An intended outcome is that pumping matches recharge and the aquifer stops declining; an unintended outcome is that a large cut in a single year could force farms to fallow fields or lay off workers.
  10. Answer: Answers vary but must name one rule (equal, historical, or market) and defend it on both grounds, for example arguing that an equal split is fairer to small farms while still meeting the recharge cap that protects the aquifer.

Differentiation

Support

Provide a labeled diagram of the aquifer showing recharge in and pumping out, with items 2 and 5 partially worked, so students can anchor the overdraft and percent-reduction calculations before moving to the allocation questions.

Extension

Ask students to design a phased cap that reaches the 12,000-acre-foot limit over five years instead of one, state each year's total, and explain why a gradual reduction might be easier for the farms to accept than an immediate cut.

ELL supports

Pre-teach "recharge," "overdraft," "cap," and "allocation" with the aquifer diagram and simple arrows for water in and water out. Allow students to answer items 3, 7, and 8 with short phrases, and provide a worked percent-reduction example.