Although most of the Earth's surface is covered with water, the majority of it is salty. Only a very small fraction is freshwater. All living beings—people, animals, birds, and plants—depend on freshwater to survive. It is essential for drinking, growing crops, and carrying out daily activities.
To understand the distribution of water on Earth, imagine if all the water on Earth were in a single glass ($200\text{ ml}$), then the available freshwater would only be as much as in a single teaspoon ($5\text{ ml}$)!
Johads in Rajasthan are traditional small earthen dams built to collect rainwater and recharge groundwater.
Water exists in three distinct forms in nature:
Water changes its form depending on temperature:
The constant circular movement of water in nature is called the water cycle.
When it rains, some water is soaked up by the soil and sinks through the layers of soil and rocks. This water stored deep underground is called groundwater.
Surface water includes rivers, ponds, and lakes. Rivers typically begin their journey high up in the mountains from melting glaciers and flow down across the land.
Freshwater habitats support a rich variety of plants and animals, each with unique adaptations to survive in water.
Organisms in aquatic ecosystems depend on each other for food, forming a food chain (e.g., plants are eaten by small fish, which are eaten by big fish, which are then eaten by birds or crocodiles).