Earth's Fresh Water

Water on Earth

• Earth's surface is mostly water covered. Most of that water is in our oceans, leaving only 3% freshwater.
• Water exists on Earth in all three phases: solid, liquid, and gas.
• The water cycle moves water from the hydrosphere to the atmosphere to the land and back again.
• The major processes of the water cycle include evaporation and transpiration, condensation, precipitation and return to the oceans via runoff and groundwater supplies.

Surface Water

• One way water returns to the oceans is through rivers and streams.
• Streams begin in higher elevations, with many tributaries joining together as it flows to lower elevations.
• A mature river will develop a floodplain and may eventually form a delta where the river meets the ocean.
• Water temporarily resides in ponds and lakes, which are mostly freshwater.
• Scientists study lakes, wetlands, and estuaries because they are biologically important areas.
• Flooding is part of the natural cycle of all rivers, which enriches floodplains with important nutrients.
• Flooding produces difficulties for humans living on or near the floodplain and in coastal areas, particularly when levees break.

Ground Water

• Groundwater, water that infiltrates the ground, forms our largest source of readily available freshwater.
• The water table forms the top of the zone of saturation, where pore spaces in sediment or rock are completely filled with water.
• Aquifers are underground areas of sediment or rock that hold groundwater.
• In steep areas, where groundwater intersects the ground surface, a spring or seep can form.
• If groundwater is heated by magma, it can form hot springs and geysers.
• In order to access groundwater supplies, humans drill wells and pump water from the ground.