Unit 4: Earth Systems & Global Water Dynamics

Watershed

A defined area of land where all surface water converges to a single point at a lower elevation.

Drainage basin

Another term for watershed, an area where surface water drains into a common outlet.

The Divide

The highest geographic points that separate one watershed from another.

Headwaters

The source geographic point of a river or stream.

Tributaries

Smaller streams and rivers that flow into a larger main river.

Mouth

The point where a river flows into a larger body of water.

Delta

A landform at the mouth of a river formed by sediment deposition.

Area (Watershed characteristic)

A large watershed may hold more water but release it more slowly than a small one.

Length & Slope

Influences water velocity and runoff; steep slopes lead to erosion whereas gentle slopes allow infiltration.

Soil Type (Sandy)

Allows high infiltration and low runoff due to high permeability.

Soil Type (Clay)

Causes high runoff and low infiltration due to low permeability.

Vegetation (Watershed role)

Plants slow down runoff, anchor soil, and filter pollutants.

Human Impacts on Watersheds

Activities like development alter natural hydrology, leading to flash floods and pollution.

Impermeable Surfaces

Structures that prevent water infiltration, increasing runoff and flooding risk.

Deforestation

The removal of trees that destabilizes soil and leads to sedimentation in rivers.

El Niño

A warm phase in the ENSO cycle characterized by weakened trade winds and suppressed upwelling.

La Niña

A cool phase in the ENSO cycle characterized by stronger trade winds and enhanced upwelling.

Normal Conditions (ENSO)

Characterized by strong trade winds blowing from East to West across the tropical Pacific.

Ecological Impact (Upwelling)

Nutrient-rich cold water rising to replace warm water supports marine life and fishing industries.

Trade Winds

Strong winds that blow across the tropical Pacific, influencing ocean currents and climate.

Weather Impacts (El Niño)

Includes increased rainfall and flooding in South America, and droughts in Australia.

Weather Impacts (La Niña)

Includes drought conditions in South America, and heavy monsoons/flooding in Australia.

Ozone confusion in El Niño

El Niño is a natural climate pattern and not caused by global warming or ozone depletion.

Watershed Boundaries

Defined by topography; do not align with political borders affecting management.

El Niño impacts

A climate pattern causing severe weather changes and redistributing rainfall globally.

Human alteration of watersheds

Activities that disrupt natural flow and drainage in watersheds resulting in environmental issues.

Flooding and erosion

Consequences of steep slopes and impermeable surfaces affecting watershed health.

Memory aid for El Niño

'El Niñ-NO' signifies lack of wind, upwelling, and fish due to warm ocean conditions.

Memory aid for La Niña

'La Niña is MEAN-ya' indicates extreme conditions in the Pacific due to strong trade winds.