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The Earth, often referred to as a remarkable blue marble, especially by the fortunate few who have observed it from space, owes its distinct appearance to the vast amount of water present on its surface. While water itself is not inherently blue, it emanates a bluish hue when reflecting light.
However, those of us residing on the Earth’s surface will recognize that water primarily covers our globe. Yet, an intriguing question persists: What exactly is the extent of Earth’s water coverage?
Water covers approximately 71% of the surface of the Earth, with continents and islands accounting for the remaining 29%. In other words, the seas hold 96.5% of all the water on Earth, whereas the rest of the 3.5% is lakes of freshwater and frozen water trapped in glaciers and polar ice caps. Almost all of that fresh water is in the form of ice: 69%, to be exact. If all that ice could be melted and the surface of the Earth was flawless, the sea level could rise to an altitude of 2.7 km. Apart from water on Earth that exists as ice, there is also a massive volume of water below the Earth’s surface. If you gathered all of the Earth’s freshwater into a single mass, the importance would be around 1,386 million cubic kilometers (km3).
Meanwhile, the amount of water that occurs as groundwater, rivers, lakes, and streams is little more than 10.6 million km3 or slightly more than 0.7%. When viewed in this light, freshwater’s limited and valuable characteristics become abundantly evident.
But how much of Earth is covered with water? This includes not only the Earth’s surface but also its inside. According to scientists, the total mass of the Earth’s seas is 1.35 x 1018 metric tonnes, or 1/4400 the overall mass. In other words, although covering 71% of the Earth’s surface, the waters constitute only 0.02% of our planet’s overall mass. Two of our planet’s long-standing mysteries are the genesis of water on its surface and the reality that it contains a more significant amount than almost every other rocky planet in the Solar System.
Oceans cover the majority of the Earth’s surface. Oceans contain approximately 97.2% of the Earth’s surface water. Five oceans surround each continent. Because the average depth of the oceans is 2.7 kilometers, the amount of water is approximately 1,338,000,000 cubic kilometers. The oceans are the cornerstone of the water cycle. Water moves in three natural stages: condensation, evaporation, and surface runoff. The ocean currents are like massive conveyor belts constantly moving vast amounts of water.
Glaciers hold about 2.1% of the world’s water. Glaciers are the world’s second-largest store of water, most located in Greenland and Antarctica. Glaciers currently contain around 24,060,000 cubic kilometers of water. Water availability in glaciers varies most significantly with Ice Ages and climate change. As temperatures rise, so do sea levels. This is so as the melting ice sheets and glaciers increase total water volume. Scientists predict that by 2100, the sea level will rise 32 to 68 inches.
Humans find groundwater everywhere as a secret supply of water. Groundwater held within an aquifer accounts for approximately 0.65% of all water on Earth. There are two types of groundwater: saltwater groundwater and fresh groundwater. Fresh groundwater accounts for around 45% of the water that exists in the ground. Whereas saline groundwater accounts for approximately 55%. Groundwater contains over one hundred times as much freshwater as streams and lakes combined. Furthermore, groundwater is difficult to extract, recharge and readily contaminated. As a result, groundwater is a precious resource from which humans take in times of need.
Lakes hold only 0.009% of all water. For instance, the Great Lakes are a source of fresh water, accounting for around 21% of all lakes of freshwater on Earth. Lake Baikal in Russia contains the equivalent of all five major lakes. Even though rainfall carries salts and minerals into rivers and lakes, they are predominantly freshwater. This happens because their minerals are washed away and transferred to the nearest ocean’s outflow. In contrast to salty oceans, lakes and rivers have their minerals regularly rinsed away.
Soil is the topmost layer that promotes plant development and agriculture. Soil moisture accounts for only 0.005% of worldwide water distribution. Soils comprise half minerals and half open space, all inside the top few centimeters of the Earth’s surface. It is frequently combined with organic material, also known as humus.
Mountains with Flowing Rivers, Treeless Landscapes, Streams, wetland areas, and marshes hold only 0.001% of the total. Lastly, just 0.001 per cent of water is in the environment or living organisms and plants as vapour. Everything upstream in a river ends up downstream. Highly connected systems of streams catch precipitation within the watershed or catchment basin. They zig-zag their way to a larger water body like a river or lake. Wetlands are recesses on the ground’s surface typically associated with specific vegetation. These habitats are essential for biodiversity and robust ecosystems.
Over 96 per cent of the water on the Earth’s surface is saline water in the seas and oceans. Water dropping from the sky and flowing into streams, rivers, lakes, and groundwater provide people with the daily water required to survive. Water on the Earth’s surface is easily visible, and you might think that the water cycle may be that rainfall fills rivers and lakes. However, the unseen water beneath our feet is also vital to life. Even if you only see water on the Earth’s outermost layer, there is much more freshwater kept within the Earth’s crust than in liquid form. Part of the water that you see streaming into rivers is caused by groundwater seepage into river bottoms. Water from precipitation continually seeps into the Earth, replenishing aquifers, while water in the ground fills rivers through seepage.
Here are some numbers to consider:
The Earth is an ecosystem made up of water. Water covers around 71% of the Earth’s surface, while the seas contain approximately 96.5 percent of all water. Water can also be found in the air as water vapor, rivers and lakes, icecaps and glaciers, soil moisture and aquifers, and even in us. Water never stands still. Our planet’s water supply is continuously migrating from one location to the next and from one form to another, thanks to the water cycle. Without the water cycle, everything would get quite dull!
Also Read: Lack of Clean Water: A Global Concern