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

Chapter: Rocks, Landscapes & Water

What these drills covers

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

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

Vocabulary used: porosity, permeability, recharge.

Problem 1

Recharge is 60 units and total output is 85. Find storage change.
Answer and explanation

-25 units

60 − 85 = −25.

Problem 2

How can paving a large area affect its water budget?
Answer and explanation

It can reduce infiltration and increase rapid runoff, changing recharge and flow timing.

Problem 3

Porosity describes the proportion of a rock that is
  1. solid
  2. pore space
  3. water
  4. mineral
Answer and explanation

pore space

Porosity is the fraction of the volume that is void space.

Problem 4

Permeability describes how easily
  1. a rock melts
  2. water moves through connected pores
  3. a rock breaks
  4. minerals form
Answer and explanation

water moves through connected pores

A rock can be porous but impermeable if the pores are not connected.

Problem 5

An aquifer is recharged at 40 million litres a year and pumped at 55 million. What is the annual deficit, in million litres?
Answer and explanation

15 million litres

55 − 40 = 15 million litres drawn from storage each year.

Problem 6

The water table is the
  1. top of the ground
  2. upper surface of the saturated zone
  3. bottom of an aquifer
  4. surface of a river
Answer and explanation

upper surface of the saturated zone

Below it the pore spaces are full of water; above it they are not.

Problem 7

Explain why a watershed boundary follows high ground.
Answer and explanation

Water runs downhill, so the ridge line divides which way precipitation flows: rain falling on one side drains to one river system and on the other side to another. Tracing the highest ground around a river's drainage therefore traces the boundary of the area that feeds it, which is what a watershed is.

Response criteria

  • State a scientifically accurate conclusion.
  • Show the data, mechanism, or calculation that supports it.
  • Include units, conditions, or limits where relevant.

Problem 8

Explain why groundwater contamination is harder to remedy than river pollution.
Answer and explanation

Groundwater moves very slowly through pore spaces, so a contaminant spreads gradually and persists for years or decades rather than being flushed away. It is also hidden, so contamination is often detected long after it began, and treating water spread through rock is far harder than treating a flowing channel. Prevention matters more here than cleanup.

Response criteria

  • State a scientifically accurate conclusion.
  • Show the data, mechanism, or calculation that supports it.
  • Include units, conditions, or limits where relevant.

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