Chapter 10 – The Hydrologic Cycle

Reserves of Water on Earth

Water is stored in oceans, glaciers, ice caps, groundwater, lakes, rivers, soil moisture, and the atmosphere. Freshwater is mainly found in glaciers and groundwater.

Adhesion vs. Cohesion

Adhesion is water sticking to other surfaces; cohesion is water molecules sticking to each other. These properties help water move through soil and plant roots.

Water Use in Developed vs. Developing Nations

Developed nations use more water for industry and households; developing nations use most water for agriculture. Globally, agriculture is the largest water use.

Components of the Hydrologic Cycle

Includes evaporation, condensation, precipitation, infiltration, runoff, and transpiration. These processes move water through Earth’s systems and connect land, air, and water.

Hydrologic Cycle and Climate Change

Climate change alters evaporation and precipitation patterns, intensifying droughts and floods and disrupting water availability.

Infiltration vs. Runoff

Infiltration is water soaking into the ground; runoff is water flowing over land. Soil type and land cover influence which occurs.

Two Main Types of Aquifers

Unconfined aquifers are recharged by surface water easily; confined aquifers are trapped between layers and recharge slowly.

Gray Water Use

(from sinks, showers) can be reused for irrigation or flushing toilets, reducing freshwater demand.

Hadley Cells and Climate

Rising air at the equator brings rain (rainforests), sinking dry air around 30° creates deserts. Explains global climate patterns.

Rain Shadows

Moist air rises over mountains, cools, and rains on the windward side. Dry air descends on the leeward side, creating deserts.

Cloud Formation and Precipitation

Warm air rises, cools, and condenses into clouds. When water droplets combine and become heavy, they fall as precipitation.

Water Quality vs. Quantity

Water quantity is how much is available; water quality is how clean or safe it is. Both affect human and ecosystem health.

Saltwater Intrusion

Overdrawing groundwater near coasts lets saltwater seep in, contaminating supplies. Can be reduced by managing water use and recharging aquifers.

Major Water Issues

Include pollution, overuse, drought, flooding, and access to clean water. These threaten ecosystems, health, and food production.