Overview
This lecture covers the hydrologic (water) cycle, focusing on key terms, reservoirs, movement of water in ecosystems, and human impacts on water pathways.
The Hydrologic Cycle Basics
- The hydrologic cycle describes how water moves through the ecosystem in different forms: vapor, liquid, and ice.
- All living things require water, and its availability is crucial for survival.
- Water can exist in the atmosphere, on the surface, or underground, changing form due to temperature and pressure.
Water Reservoirs
- Major water reservoirs are oceans (97% of Earth's water), freshwater sources, glaciers, ice caps, and underground aquifers.
- Oceans store salty water; freshwater is critical for human and animal survival.
- Glaciers and ice caps hold most freshwater but are largely inaccessible.
- The atmosphere contains a small but crucial amount of water vapor for precipitation and plant growth.
Key Processes in Water Movement
- Evaporation: Liquid water turning into vapor, mainly from oceans and bodies of water.
- Transpiration: Water released from plants, important for plant productivity and photosynthesis.
- Condensation: Water vapor becoming liquid to form clouds.
- Precipitation: Water falling from clouds as rain, snow, etc.
- Infiltration: Water soaking into soil, replenishing underground reservoirs (water table).
- Runoff: Water flowing over the land into surface waters.
Watersheds and Human Impact
- A watershed is an area where all water drains to a common point, including rivers and their tributaries.
- Human activities like urban development and agriculture alter infiltration and runoff patterns.
- Paving over natural areas decreases infiltration and increases runoff, disrupting natural water flow.
Key Terms & Definitions
- Hydrologic cycle — movement of water through the environment in various forms.
- Evaporation — process where liquid water becomes vapor.
- Transpiration — release of water vapor from plants.
- Condensation — conversion of water vapor to liquid form, forming clouds.
- Precipitation — water that falls to Earth's surface from clouds.
- Infiltration — water soaking into the soil and replenishing underground sources.
- Runoff — water flowing over the ground into bodies of water.
- Water table — upper level of groundwater underground.
- Watershed — land area where all water drains to a single point.
Action Items / Next Steps
- Review terms and processes of the hydrologic cycle for mastery.
- Complete any assigned practice questions or diagrams about water movement and reservoirs.