Water systems
Hydrological cycle
The hydrological or water cycle is the continuous water movement within the Earth’s atmosphere, surface, and underground. This process can be shown using a systems diagram with stores as boxes and flows as arrows.
Solar radiation and gravity drive water movements in the hydrosphere. Heat causes water to evaporate and water vapour to form. Gravity causes water to drain through the soil and into rivers to the sea.
Main Stores in the Hydrological Cycle
- Ocean (96.5%)
- Surface Freshwater: Lakes, rivers, and oceans (0.02%)
- Glaciers and ice caps (1.7%)
- Groundwater: Aquifers and underground reservoirs (1.7%)
- Biosphere: Water within living organisms (0.0001%)
Main Flows in the Hydrological Cycle
- Evaporation: Water from oceans, lakes, and rivers turns into vapour due to solar radiation.
- Transpiration: Water vapour is released by plants during photosynthesis.
- Condensation: Water vapour cools to form clouds.
- Precipitation: Rain, snow, or hail falling to Earth.
- Runoff: Water flows over land into rivers, lakes, and oceans.
- Infiltration: Water seeps into the soil, replenishing groundwater.
- Percolation: Water moves deeper into the ground.
