Welcome to Global Water Resources!

Welcome to one of the most important topics in Human Geography! While you might have studied the "water cycle" in science or physical geography, this chapter focuses on the Human Water Cycle. We are going to look at where the world's water is, how humans "interfere" with its natural flow, and why some places have plenty of water while others struggle with water stress. Don't worry if some of the terms sound technical—we will break them down piece by piece!

1. Types and Global Pattern of Water Resources

Water is everywhere, but most of it isn't easy for humans to use. Here is the breakdown of what we have on Earth:

  • Saltwater: About \( 97\% \) of all Earth's water is in the oceans. It is too salty for drinking or crops without expensive treatment.
  • Freshwater: Only about \( 3\% \) of Earth’s water is fresh. However, most of this is "locked away" in glaciers and ice caps.
  • Accessible Freshwater: This is the water we can actually reach in rivers, lakes, and underground (groundwater). This makes up less than \( 1\% \) of all water on Earth!

The Global Pattern: Water is not spread out evenly. Some areas (like the Tropics or Canada) have a surplus (extra water), while others (like Northern Africa or the Middle East) have a deficit (not enough water). This is due to climate, but also how many people are trying to use the same water source.

Quick Review: Most of the world's water is salty. Of the tiny amount that is fresh, most is frozen. Humans rely on a very small "slice" of the total water pie!

2. The Human Water Cycle

In physical geography, you learn about evaporation and rain. In human geography, we look at how humans "plumb" the planet. This is called the Human Water Cycle. It follows these stages:

  1. Capture: Taking water from the natural environment (e.g., building a dam or pumping from a well).
  2. Management: Storing and moving water to where it is needed (e.g., reservoirs and pipes).
  3. Use: Using water for homes, factories, or farms.
  4. Disposal: Getting rid of "used" water (e.g., through sewers).
  5. Reuse: Treating "dirty" water so it can be used again (e.g., recycling grey water for gardens).

Did you know? The human water cycle is basically a "detour" we force the natural water cycle to take so we can survive and make money!

3. How Human Activities Modify the Water Cycle

We don't just use water; we change how it moves through the environment. The syllabus highlights six ways we do this:

A. Agriculture: This is the biggest user of water globally (about \( 70\% \) of all freshwater used). We use irrigation to water crops in dry areas, which can deplete rivers and underground stores.

B. Deforestation: Trees act like sponges. When we cut them down, there is less evapotranspiration (water vapor released by plants). This leads to more surface runoff and more frequent flooding because the "sponge" is gone.

C. Urbanisation: Cities are covered in concrete and tarmac (impermeable surfaces). Water cannot soak into the ground, so it rushes into drains and rivers very quickly, often causing "flash floods."

D. Industrialisation: Factories need huge amounts of water for cooling and manufacturing. They also often dispose of chemicals back into the water system, which can cause pollution.

E. Abstraction: This is a fancy word for "pumping water out." If we pump groundwater out of a well faster than rain can refill it, the water table (the level of underground water) drops. In coastal areas, this can lead to saltwater intrusion, where salty ocean water seeps into our fresh drinking wells!

F. Flood Management: By building levées (raised banks) or straightening rivers, we speed up the flow of water. This might protect one town but often makes flooding worse for people living further downstream.

Key Takeaway: Humans change the water cycle by changing how fast water moves (urbanisation/deforestation) and where it is stored (abstraction/dams).

The world is using more water than ever before. There are three main reasons for this "upward trend":

  • Population Growth: More people simply means more "thirsty" mouths to feed and more bodies to wash.
  • Economic Development: As countries move from LICs (Low-Income Countries) to MICs (Middle-Income Countries), people start buying washing machines, dishwashers, and cars—all of which use lots of water.
  • Dietary Changes: As people get wealthier, they eat more meat. It takes much more water to produce \( 1kg \) of beef (to grow the grain the cow eats) than it does to produce \( 1kg \) of wheat.

5. Water Stress and Scarcity

When demand for water is higher than the supply, we have a problem. Geographers use specific terms to describe this:

Water Stress

This happens when the amount of water available is not enough to meet the needs of the population during a certain period, or when poor quality limits its use.

Physical Scarcity

This is "natural" scarcity. There simply isn't enough water in the environment. Think of a desert like the Sahara. No matter how much money you have, the rain isn't falling, and the rivers aren't flowing.

Economic Scarcity

This is "human-made" scarcity. There is enough water in nature (like a big river nearby), but the country is too poor to build the pipes, dams, or treatment plants needed to get that water to the people. This is common in many LICs.

Memory Trick:
Physical = Precipitation (not enough rain).
Economic = Expensive (not enough money for pipes).

Summary: What You Need to Remember

1. Only a tiny fraction of Earth's water is accessible freshwater.
2. The human water cycle (capture, use, disposal) is our modification of the natural cycle.
3. Activities like agriculture and urbanisation change how water moves and how clean it stays.
4. Water stress is rising because of growing populations and changing lifestyles.
5. Physical scarcity is about a lack of water; economic scarcity is about a lack of infrastructure.

Note: For information on how we manage these problems (like Desalination or Rainwater Harvesting), please see the next chapter on "Management of Water Resources."