"The earth's oceans hold 97% of the world's surface water. The other 3 per cent of the earth's water is fresh water. This amount of fresh water is more than enough to meet people's needs, but it is not evenly distributed around the world"
Of that three per cent of fresh water:
- 79% is stored in glaciers and polar ice caps
- 20% is stored as groundwater, soil moisture, swamp water and permafrost
- only 1% is easily accessible fresh water.
- This means that of all the world's surface water, only 0.03% is easily accessible fresh water!
Figure 5.7 on page 107 shows the amount of precipitation (water that makes its way to the earth's surface in the forms of rain, hail, snow and dew) the each continent receives annually (per year) and what percentage of this precipitation is lost to evaporation and what becomes run-off and flows into streams, creeks and revers, or underground, to become ground water.
Different factors influence the type of water loss:
What do you notice about the differences in water loss in Australia? Of the five factors above, write a paragraph explaining which of these factors you think would affect Australia?
- Climate: warm or hot climates will have greater evaporation than cooler climates
- Vegetation: types of plants and plant cover; for example, there will be more evaporation in the grassy paddocks of a sheep farm than in denser vegetation that holds moisture.
- Soil Type: some soils are more permeable (penetrable) and allows more water to soak through
- Topography (shape of the land): steep areas will have more run-off than flatter areas
- Location: hard surfaces such as roads and pavements lead to greater evaporation than unpaved surfaces, so there is greater evaporation in cities and towns than in rural locations.
What do you notice about the differences in water loss in Australia? Of the five factors above, write a paragraph explaining which of these factors you think would affect Australia?
Table 5.6 on page 106 shows the length of time water can be stored in different ways:
Complete the interactive activity on page 107 of Pearson