Water
Water is the foundation of life and its primary essence; existence on Earth is impossible without it. Furthermore, Earth is the only planet known to harbor substantial amounts of water, rendering it uniquely capable of supporting life compared to other celestial bodies. As such, Earth is often referred to as the “Blue Planet,” signifying the critical role of water in sustaining life. Thus, water is considered one of the most significant environmental factors present on our planet.
Forms of Water
Water exists in various forms in nature, dependent on its location. The primary forms include:
Ocean Water
Approximately 71% of Earth’s surface is covered by oceans and seas, accounting for about 97.6% of the total volume of water on the planet. The average salinity of oceanic waters is about 3.5%, which equals 35 grams per liter. The presence of various straits between seas and oceans helps maintain a non-uniform salinity among these bodies of water.
Glacial Ice
Glaciers comprise water that has frozen in polar regions and at high mountain peaks. The majority of the world’s glaciers are located in Antarctica, which contains around 85% of the planet’s ice. Some glaciers can be up to 2 kilometers thick. Glacial water represents approximately 2.07% of the total water on Earth. Although this type of water is fresh and suitable for human use, it remains largely inaccessible due to its remote locations and solid state. Notably, roughly three-quarters of the Earth’s freshwater supply is found in glaciers.
Groundwater
Groundwater is water that lies beneath the Earth’s surface, stored in the soil and rock layers via their pore spaces and fractures. Studies on the water cycle reveal that rainwater disperses through various pathways. A significant portion evaporates and returns to the atmosphere; another portion flows on the surface, generating streams and rivers, while the remaining water seeps through the soil and rock, forming groundwater. The quantity of groundwater varies based on the depth of the Earth’s surface.
Surface Water
Surface water refers to the water found in rivers, streams, lakes, swamps, and ponds. The primary sources of this water include precipitation, snowmelt, and often groundwater.