The Hydrologic Cycle

Cohesion

Attraction of water molecules to other water molecules (clinging of like molecules).

Adhesion

Attraction of water molecules to different substances (clinging of unlike molecules).

Why is cohesion important?

Creates surface tension and helps water move together.

Why is adhesion important?

Helps water stick to surfaces and move through plant stems (capillary action).

Density of liquid water vs. ice

Ice is less dense than liquid water, so it floats.

Why do lakes freeze from the top down?

Ice floats because it is less dense, insulating the water below so aquatic life can survive.

Residence time of water

The average amount of time water stays in one part of the hydrologic cycle.

Where does water have the longest residence time?

Ice caps and glaciers.

Rain gauge

Instrument used to measure rainfall.

Cheugugi

The first standardized rain gauge, developed in Korea.

Doppler radar advantages

Real-time record, site-specific measurements, and high resolution.

Runoff

Water that flows across the land surface after a storm event.

Three major factors affecting runoff

Climate, soil type, and terrain.

Amazon River Basin

Tremendous runoff due to high precipitation and a massive drainage area.

Los Angeles Basin

High runoff because of intense rainfall, impervious surfaces, and hard soils.

Sandhills of Central Nebraska

Low runoff due to sandy soils, flat terrain, and dense native grasses.

Infiltration

Water soaking into the soil.

Surface detention

Water temporarily stored on the land surface before infiltrating or running off.

How does urbanization affect infiltration?

It decreases infiltration because roads and buildings create impervious surfaces.

How does urbanization affect runoff?

It increases runoff.

Why does flooding occur?

Less water is lost to surface detention, infiltration, and evapotranspiration, causing more runoff.

Why are lakes considered ephemeral?

They gradually fill with sediment over time.

Eight ways lakes form

Landslides, tectonism, glaciation, river action, animal activity, meteorite impact, volcanism, and human activity.

Lake Baikal

Oldest, largest, and deepest freshwater lake on Earth.

Lake Tanganyika

Longest and second deepest freshwater lake.

Deepest lake in the U.S.

Crater Lake, Oregon.

Wetlands

Transitional areas between land and water where the water table is at or near the surface.

Functions of wetlands

Water storage, water purification, flood mitigation/flow regulation, groundwater recharge, and local climate regulation.

Evaporation

Liquid water changing into water vapor.

Class A Pan

Instrument used to measure evaporation.

Edmond Halley's contribution

Measured evaporation and showed that significant water is lost from the Mediterranean through evaporation.

Evapotranspiration

The combined process of evaporation and transpiration.

Lysimeter

Instrument used to measure evapotranspiration by comparing planted and control tanks.

Advection fog

Forms when warm, moist air moves over a cooler surface.

Orographic fog

Forms when moist air rises over a mountain and cools.