Properties of Water

Properties of Water

• Only natural substance that exists as solid, liquid, and gas in temperatures normally found on Earth– Freezing point = 0oC (32oF)– Boiling point = 100oC (212oF)

Properties of Water

• Expands when it freezes– More dense as a liquid than a solid– Density of water = 1 g/cm3

– Density of ice = 0.91 g/cm3

Properties of Water

• High specific heat– A lot of energy is needed to change its

temperature.– Moderates air temperature

Properties of Water

• High surface tension– Cohesion– Adhesion

Properties of Water

• Universal Solvent– Dissolves many (not all) substances

The Water Cycle

The Water Cycle

• Earth’s water supply is continuously recycled.

• The overall process is powered by the Sun’s energy.

Water Storage

• Ocean– Most water on Earth

• Glaciers– Most fresh water

• Lakes• Ice/snow• Atmosphere

How Water Enters the Atmosphere• Evaporation

• Transpiration

• Sublimation

Forms of Precipitation

• Rain• Sleet• Snow• Hail• Freezing Rain

The Water Cycle

• Once water reaches Earth’s surface as precipitation, it can:– Evaporate– Infiltrate– Run off

The Water Cycle

Runoff

• Runoff is water flowing downslope along Earth’s surface.

• Runoff may – reach a stream, river, or lake– evaporate– accumulate and eventually seep into the

ground (infiltrate)

Factors that affect Runoff

• Vegetation

• Rate of Precipitation

• Soil Compaction

• Slope

Surface Water Movement

Watersheds and Divides

• Watershed– all of the land area whose water drains into a

stream system• stream system

– large river and all its tributaries

NC Watersheds

NC has 12,200 km of rivers and streams

Stream Development

Moving Water Carves a Path

• Must have an adequate supply of water • Stream begins at headwaters

Youthful Rivers

• Steep gradient (slope) • Narrow channel (downcutting)• Channel is V-shaped • Fast moving • Moves all sediment sizes • No floodplain • Rapids and waterfalls• More erosion than deposition

Youthful River

Mature Rivers

• Channel is U-shaped• Medium velocity • Moves many sediment sizes - not boulders • Small floodplain• Meanders begin to form• Erosion and deposition occur • Carries more sediment

Mature River

Old Rivers

• Very shallow gradient • Channel is wider than deep • Slow moving• Moves small-sized sediments • Wide floodplain • Meanders are abundant • Large discharge

Old River

Meandering Streams

• In a curve, the greatest speed is along the outside of the curve.– Erosion occurs along the outside of the curve.– Deposition occurs along the inside of the

curve.

Meandering Streams

Work of Streams

• A stream’s load includes all the materials that the water in a stream carries.– solution (dissolved)– suspension (carried) – bed load (pushed)

Work of Streams

• Erosion– The ability of a stream to erode materials

depends on its velocity.– Abrasion– Grinding– Dissolving

Lakes and Wetlands

Lakes and Freshwater Wetlands

• A lake is a depression that collects and holds water.

• Reservoirs are lakes made for storing water for a community’s use.

Origins of Lakes

• Natural lakes form in different ways. 1. Oxbow lakes: streams cut off meanders and

leave isolated channels of water.

2. Lakes can form when stream flow becomes blocked by sediment from landslides.

Origins of Lakes

• Natural lakes form in different ways. 3. Cirque lakes: depressions left by valley

glaciers fill with water.

4. Kettle lakes: blocks of ice left by melting glaciers melted.

5. Some lakes are formed when the ceilings of limestone caverns collapse leaving depressions that fill with water.

Lakes Undergo Change

• Lakes are temporary water-holding areas.• Eventually lakes fill in with sediment and

become part of a new landscape.

Freshwater Wetlands

• A wetland is a land area that is covered with water for a large part of the year.

• Wetlands include environments commonly known as bogs, marshes, and swamps.

Freshwater Wetlands

• Bogs receive their water from precipitation and tend to be rich in peat moss.

Freshwater Wetlands

• Marshes frequently form along the mouths of streams and in areas with extensive deltas.

• Marshes have tall grasses.

Freshwater Wetlands

• Swamps are low-lying areas often located near streams.

• Swamps have shrubs and trees.

Freshwater Wetlands

• A filtering system – Pollutants– Sediments– Pathogenic bacteria

• Habitats – Migratory birds– Water birds– Endangered species

Freshwater Wetlands

• From the late 1700s to the mid 1980s, the continental United States lost 50 percent of its wetlands.