Rank the following sources of water from largest to smallest in terms of percentage of the world’s total supply.
A) Rivers, Lakes, Groundwater, Glaciers
B) Glaciers, Groundwater, Rivers, Lakes
C) Groundwater, Glaciers, Rivers, Lakes
D) Lakes, Rivers, Groundwater, Glaciers
The Correct Answer and Explanation is:
The correct answer is B) Glaciers, Groundwater, Rivers, Lakes.
To understand the ranking, we need to know the distribution of Earth’s water resources:
- Glaciers and Ice Caps (about 68.7%): The largest portion of Earth’s fresh water is locked in glaciers and polar ice caps. These frozen bodies of water contain the vast majority of the planet’s fresh water—around 68.7%. However, because this water is frozen and largely inaccessible, it is not readily available for use by humans or other organisms.
- Groundwater (about 30.1%): Groundwater, which includes water stored in underground aquifers, comes second in terms of Earth’s total fresh water supply. Groundwater constitutes about 30.1% of the planet’s fresh water, making it a crucial source for drinking, irrigation, and industrial use. This water is accessible but can be difficult to manage in some areas, as it requires pumping and can be vulnerable to contamination.
- Rivers (about 0.49%): Rivers represent a much smaller proportion of Earth’s fresh water, at approximately 0.49%. Although rivers are essential for water supply, agriculture, transportation, and ecosystems, they account for a very small fraction of the world’s total water. This is partly because rivers are part of a continuous cycle that involves water from glaciers, precipitation, and groundwater.
- Lakes (about 0.26%): Lakes contain even less fresh water than rivers. They make up around 0.26% of the world’s total water supply. Although lakes are vital sources of water for many regions and support aquatic life, they represent a small percentage of global water resources.
Explanation: The hierarchy starts with glaciers, which hold the most water, followed by groundwater, which is the second-largest source. Despite being critical for human use, both rivers and lakes are relatively small in comparison. The small percentages reflect the large proportion of Earth’s water being in oceans and frozen form, which are not readily accessible or usable in the way fresh water from lakes, rivers, and groundwater is.