Water: The Essence of Life

Key Concepts

Freshwater and Saltwater

Most of the Earth's surface is covered with water, but the majority of it is salty (found in oceans). Freshwater is a very small fraction of the total water on Earth—if all Earth's water were in a glass, the freshwater would be only as much as in a teaspoon!

• Salt Pans: Areas like the salt pans of Gujarat are used to dry seawater to collect salt.
• Freshwater Sources: Rivers, lakes, ponds, glaciers, and groundwater.

Forms of Water

Water exists in three distinct states:

1. Liquid: Found in rain, rivers, and oceans.
2. Solid: Found as ice, snow, and glaciers.
3. Vapour (Gas): Found as steam or invisible moisture in the air.

The Water Cycle

The water cycle is the continuous movement of water between the Earth's surface and the atmosphere:

• Evaporation: Heat from the Sun turns surface water into water vapour.
• Condensation: Water vapour cools down to form droplets, which create clouds.
• Precipitation: Droplets fall back to Earth as rain, snow, or hail.

Groundwater and Recharge

Rainwater that is soaked up by the soil and stored deep underground in layers of rocks is called groundwater.

• Accessing Groundwater: We use wells, borewells, tube wells, and handpumps to draw this water.
• Recharge: Open, uncovered areas like lawns and forests allow water to seep into the ground (permeable surfaces).
• Challenges: Cemented surfaces in cities (impermeable surfaces) prevent groundwater from getting recharged.
• Conservation: Soak pits, ponds, and planting trees help in recharging groundwater.

Surface Water and Topography

Rivers and lakes are major surface water sources.

• Flow: Water always flows from higher ground (mountains) to lower ground (valleys) due to gravity.
• Land Shape: The shape of the land determines whether a river flows towards the Arabian Sea or the Bay of Bengal.
• Luni River: A unique river in India that ends in the marshy lands of the Rann of Kutch instead of draining into the sea.

Life in Water (Adaptations)

Aquatic plants and animals have special features to survive in water:

• Animals: Fish have fins and streamlined bodies. The Fishing Cat has partially webbed paws for swimming.
• Plants:
  • Floating: Water Hyacinth and Lily have leaves that float.
  • Waxy Coating: Leaves of plants like the Lotus have a waxy, hydrophobic coating that makes them waterproof and prevents rotting.
  • Rooted: Some have roots in the pond bed while flowers float.
  • Submerged: Some plants live completely underwater.

Interdependence and Food Chains

Organisms in a water body depend on each other for survival. A river food chain (e.g., small fish being eaten by big fish, which are eaten by herons or humans) shows how energy moves through the ecosystem. The disappearance of even one species can disrupt the entire balance.