Water & Land Resources — Drills · Grade 12 Science

Chapter: Energy, Water & Material Resources

What these drills covers

By the end of Water & Land Resources you should be able to:

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

Vocabulary used: freshwater, watershed, aquifer, irrigation.

Problem 1

Most of Earth's water is...
  1. salty ocean water
  2. freshwater in lakes and rivers
  3. frozen in home freezers
  4. underground oil
Answer and explanation

salty ocean water

About 97% of Earth's water is salty ocean water, which is why usable freshwater is so limited.

Problem 2

An underground layer of rock or sediment that stores and transmits groundwater is called a(n)...
  1. watershed
  2. aquifer
  3. reservoir
  4. glacier
Answer and explanation

aquifer

An aquifer holds groundwater underground; wells pump water up from it.

Problem 3

For this supplied allocation model, In a region, agriculture uses 70% of the freshwater and industry uses 22%, with homes using the rest. What percent do homes use?
Answer and explanation

8 %

The uses total 100%: 100 - 70 - 22 = 8% for homes.

Problem 4

Everything that happens on the land within a watershed matters to its water because...
  1. land never affects nearby water
  2. watersheds are located deep underground
  3. whatever is on the land drains into the shared water body
  4. water in a watershed flows uphill
Answer and explanation

whatever is on the land drains into the shared water body

A watershed drains all its land to a common outlet, so pollution or sediment on the land ends up in the shared river, lake, or reservoir.

Problem 5

Explain why usable freshwater is so scarce even though Earth is called the 'blue planet.'
Answer and explanation

Although water covers most of Earth's surface, about 97% of it is salty ocean water that we can't drink or use to irrigate crops without expensive desalination. Most of the remaining 3% of freshwater is locked in ice caps and glaciers or stored deep underground, leaving less than 1% of all water as accessible liquid freshwater in lakes, rivers, and shallow groundwater.

Problem 6

A river supplies 8 billion cubic meters of water per year, and agriculture takes 75% of it. A new efficient-irrigation program cuts agriculture's use by 20%. How many billion cubic meters does the program save per year?
Answer and explanation

1.2 billion m 3

Agriculture uses 0.75 x 8 = 6 billion m 3. A 20% cut saves 0.20 x 6 = 1.2 billion m 3 per year.

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