Grade 8 Science: Water Systems on Earth

Study Notes

This unit explores Earth's water systems
Topics covered include water's effects, distribution, the water cycle, differences between ocean and fresh water, sources of fresh water, and the impact of glaciers and global warming.

Images of the Churchill River and large ocean waves illustrate water's impact.
Water use categorized by uses: Household, Personal, and Recreational (as buttons on a screen).

Only 3% of Earth's water is fresh water.
Two-thirds of fresh water is frozen in ice sheets.
Only 1% of the Earth's fresh water is readily available.
Earth's water broken down: Saline (oceans) 97%, Fresh water 3%.
Fresh water further broken down into: Ground water 30.1%, Ice caps & Glaciers 68.7%, Surface water 0.3%, Rivers 2%, Lakes 87%, Swamps 11% , Other 0.9%.
This detailed breakdown of water distribution illustrates the relative abundance of different types of water on Earth.

Water constantly cycles between liquid, gas (vapor), and solid (ice) forms.
Evaporation from the ocean contributes about 80% of the water vapor in the atmosphere
Precipitation, runoff, groundwater, and cloud formation are key aspects of the water cycle.
The sun's energy drives the water cycle.

Salinity: The amount of salt dissolved in a specific amount of water.
- Ocean water salinity is about 35 parts per thousand (ppt), and varies by location.
- Fresh water has tiny amounts of salt
Density: The amount of mass of a substance in a volume.
- Ocean water is more dense than fresh water.
Freezing point: Water freezes at 0°C (fresh water) and -1.9°C (sea water)

Lakes, ponds, and wetlands
Streams and rivers.
Groundwater: Precipitation that sinks into the ground and collects in rock pores
- Wells can be drilled to reach groundwater.
Glaciers: Moving masses of snow and ice (mostly from snowy areas), found in cold areas.
Drainage basins: Areas of land that drain water into a particular body of water.

Glaciers are moving masses of snow and ice.
They are found in areas with persistent cold, snow accumulates year-round.
Glaciers store a large amount of water for the water cycle (slowing it down), and are released during warmer periods.
They provide information on past climates.
The images show current glacier melt from past glacier photos.

Drainage basins are areas of land that drains water into a body of water such as a river, pond, lake, or ocean.
Divides separate one drainage basin from another (e.g., The Continental Divide).
Canada has multiple drainage basins

Factors like salinity and temperature influence the types of organisms that can survive in a particular area.
- Salinity affects ocean life whereas temperature affects oxygen dissolved in water
Convergence of currents (e.g., Labrador and Gulf Stream) affects productivity, icebergs formation, and animal migration.