How does the water cycle provide fresh water for plants and animals, and what happens to the water once it drains into the seas?

Sourav PanNovember 12, 2024

Answered

The water cycle, also known as the hydrologic cycle, is a continuous process that plays a vital role in providing fresh water for plants and animals, as well as maintaining ecological balance. Here’s how the water cycle functions and what happens to the water once it drains into the seas.

How the Water Cycle Provides Fresh Water

1. Evaporation and Transpiration:
   • Water from oceans, lakes, rivers, and other bodies evaporates into the atmosphere due to solar energy. This process converts liquid water into water vapor.
   • Transpiration is another crucial process where plants absorb water through their roots and release it as vapor through small openings called stomata in their leaves. Together, evaporation and transpiration are referred to as evapotranspiration, which significantly contributes to moisture in the atmosphere.
2. Condensation:
   • As water vapor rises, it cools and condenses into tiny droplets, forming clouds. This process purifies the water because impurities are left behind during evaporation.
3. Precipitation:
   • When cloud droplets combine and grow larger, they eventually fall back to Earth as precipitation (rain, snow, sleet, or hail). This precipitation replenishes freshwater sources on land, including rivers, lakes, and groundwater.
4. Infiltration and Surface Runoff:
   • Some of the precipitation infiltrates into the ground, replenishing groundwater supplies. This groundwater is crucial for sustaining plant life during dry periods.
   • Excess water that cannot be absorbed by the soil flows over land as surface runoff, eventually returning to oceans and rivers.

Importance of Fresh Water for Plants and Animals

• Freshwater is essential for all living organisms. Plants use it for photosynthesis, nutrient transport, and metabolic processes. Animals rely on freshwater for drinking, habitat, and food sources.
• The availability of fresh water directly affects biodiversity and ecosystem health. Healthy ecosystems depend on a consistent supply of freshwater to support various life forms.

What Happens to Water Once It Drains into the Seas

1. Return to Oceans:
   • The water that drains from land surfaces eventually flows back into the oceans through rivers and streams. The oceans hold about 97% of Earth’s total water supply.
2. Evaporation from Oceans:
   • Once in the ocean, this water can again evaporate due to solar heating, continuing the cycle. The ocean is responsible for approximately 86% of global evaporation and 78% of precipitation occurs over ocean surfaces .
3. Salinity Changes:
   • The movement of freshwater into the oceans can affect salinity levels. Processes such as precipitation (which adds freshwater) and evaporation (which concentrates salts) influence ocean salinity dynamics .
4. Nutrient Cycling:
   • The drainage of freshwater into oceans also carries nutrients from terrestrial ecosystems that can support marine life. This nutrient input is vital for sustaining marine food webs.
5. Long-Term Storage:
   • Water in the ocean can remain there for long periods before being evaporated again or cycled through various processes like ocean currents or upwelling.