Unit 10: The Water Cycle

The water cycle, also known as the hydrological cycle, describes the continuous movement of water on, above, and below the Earth's surface. It involves various processes such as evaporation, condensation, precipitation, infiltration, runoff, and transpiration, which circulate water between the atmosphere, oceans, land, and living organisms.

Key components and processes of the water cycle include:

1. Evaporation: Evaporation is the process by which water from oceans, lakes, rivers, and other surface water bodies is converted into water vapor due to heat from the sun. This vapor rises into the atmosphere.

2. Condensation: As water vapor rises into the atmosphere, it cools and condenses to form clouds. Condensation occurs when water vapor changes back into liquid water droplets, usually on tiny particles called condensation nuclei.

3. Precipitation: Precipitation is the release of moisture from clouds in the form of rain, snow, sleet, or hail. It occurs when water droplets or ice crystals in clouds grow large enough to fall under the influence of gravity.

4. Infiltration: Infiltration is when precipitation seeps into the ground and replenishes groundwater supplies. Some infiltrated water may eventually reach aquifers, underground reservoirs of water stored in porous rock layers.

5. Runoff: Runoff refers to the flow of water over the Earth's surface, typically due to precipitation that exceeds the soil's infiltration capacity. Runoff collects in streams and rivers and ultimately flows into oceans, lakes, or other surface water bodies.

6. Transpiration: Transpiration releases water vapor from plants' leaves into the atmosphere. Plants absorb water from the soil through their roots and release it into the air through small openings called stomata.

7. Sublimation and Deposition: Sublimation is the direct transition of water from the solid phase (ice or snow) to the vapor phase without passing through the liquid phase. Deposition is the reverse process, where water vapor changes directly into solid ice or snow.

The water cycle is driven by solar energy and atmospheric circulation patterns and plays a critical role in regulating Earth's climate, distributing freshwater resources, supporting ecosystems, and shaping landscapes. It is a dynamic and interconnected process that influences weather patterns, precipitation distribution, and water availability for human activities and natural systems.