Groundwater, Watersheds & Water Budgets — Practice · Grade 9 Science

Chapter: Rocks, Landscapes & Water

What this practice covers

By the end of Groundwater, Watersheds & Water Budgets you should be able to:

8 questions, numeric, multiple choice and written answer, each with a worked explanation.

Vocabulary used: porosity, permeability, recharge.

Problem 1

Inputs are 120 units and outputs are 100. Find change in storage.
Answer and explanation

20 units

120 − 100 = +20.

Problem 2

High porosity always guarantees high permeability.
  1. True
  2. False
Answer and explanation

False

Pores must be well connected and large enough to transmit water readily.

Problem 3

Why can pumping create a long-term problem in a renewable aquifer?
Answer and explanation

Withdrawals may exceed recharge over the relevant timescale.

Problem 4

A simplified basin receives 120 units of water, loses 85 naturally and has 20 withdrawn. Find storage change. Explain the reasoning in your own words.
Answer and explanation

Storage rises by 15 units in this supplied model, assuming no omitted flows.

Total output=85+20=105 units.

Change=120−105=15 units.

Response criteria

  • Use the stated conditions.
  • Show the evidence or calculation.
  • Explain the conclusion and any stated limitation.

Problem 5

A water store receives 80 units and loses 95 units in a period. Find its change. Show the reasoning, not just the conclusion.
Hints

All quantities must cover the same area and time.

Answer and explanation

80−95=−15 units, a decrease in storage.

Problem 6

How can pumping affect a stream connected to an aquifer?
Hints

State what the supplied observations or conditions establish, and separate that from any assumption.

Answer and explanation

Lower groundwater levels can reduce groundwater discharge to the stream or induce flow from it, depending on the connection.

Problem 7

Pumping can change the gradient toward a wellPumping can change the gradient toward a wellPumping draws down a local water levelCompare withdrawal, recharge and nearby measured heads.
Original ideal unconfined pumping section. The lowered line represents drawdown in porous material, not an emptied underground bowl. Actual flow and drawdown depend on geological layers, boundaries and time; arrows are not a contaminant-travel prediction.
Interpret the supplied visual model. What records would help distinguish increased pumping from reduced recharge as a cause of declining well levels?
Answer and explanation

Compare pumping volumes/times, rainfall and recharge estimates, water levels in several wells and local geology. A single falling-level series cannot distinguish all causes.

Trace the arrows toward the pumping well and the lowered blue water-table line. The geometry represents an unconfined teaching model.

Compare pumping volumes/times, rainfall and recharge estimates, water levels in several wells and local geology. A single falling-level series cannot distinguish all causes.

Response criteria

  • Read the labeled quantities, reference frame or objects correctly.
  • Explain the relation between the visual evidence and the mechanism.
  • Keep the drawing’s stated assumptions and limits in the conclusion.

Problem 8

A catchment begins with 300 m³ of stored water. Over one month it receives 100 m³ and loses 70 m³ by outflow/evapotranspiration plus 45 m³ by withdrawal. Find storage change and final storage. Explain why high porosity alone would not guarantee fast recharge.
Answer and explanation

Storage change is 100−70−45 = −15 m³ and final storage is 285 m³. Transmission also depends on connected pathways, permeability, gradients and conditions; porosity alone is a storage fraction.

Combine outputs: 70+45 = 115 m³.

Change is −15 m³; add to initial 300 m³ to get 285 m³.

Distinguish pore-space amount from connected transmission.

Response criteria

  • Use the stated measurements or conditions, with correct units.
  • Connect the result to the physical mechanism or evidence relationship.
  • Identify the assumption, model limit or further evidence requested.

Browse all courses