Final answer:
The approximate percentage of the earth's freshwater that is groundwater is 30%, thus the correct option is c.
Explanation:
Groundwater is the water that is stored beneath the earth's surface in soil and rock formations. It plays a crucial role in sustaining life and is a vital source of freshwater for human activities, such as drinking, irrigation, and industrial use. In order to understand the percentage of the earth's freshwater that is groundwater, we must first understand the concept of the earth's total water resources.
According to the United States Geological Survey (USGS), the earth's total water resources can be divided into three main categories: oceans and seas, ice caps and glaciers, and groundwater. Oceans and seas hold approximately 97% of the earth's water, while ice caps and glaciers hold about 2%. This leaves groundwater with only a small percentage of the earth's total water resources.
To calculate the approximate percentage of the earth's freshwater that is groundwater, we can use the following formula:
Percentage of groundwater = (Volume of groundwater / Total volume of freshwater) x 100
First, we need to calculate the volume of groundwater. According to the USGS, the total volume of groundwater is estimated to be around 8.4 million cubic kilometers (km^3). Next, we need to calculate the total volume of freshwater, which includes all sources of freshwater such as lakes, rivers, and groundwater. The total volume of freshwater is estimated to be around 35 million km^3.
Substituting these values into the formula, we get:
Percentage of groundwater = (8.4 / 35) x 100 = 24%
This calculation tells us that groundwater makes up approximately 24% of the earth's total freshwater resources. However, the question specifically asks for the percentage of groundwater in relation to the earth's total water resources. To get this percentage, we need to include the volume of seawater as well.
The total volume of water on earth is estimated to be around 1.4 billion km^3, which includes both freshwater and seawater. To calculate the percentage of groundwater in relation to the earth's total water resources, we can use the following formula:
Percentage of groundwater = (Volume of groundwater / Total volume of water) x 100
Substituting the values, we get:
Percentage of groundwater = (8.4 / 1.4 billion) x 100 = 0.0006%
This calculation tells us that groundwater makes up only 0.0006% of the earth's total water resources. This is a significantly small percentage, but it is still a vital source of freshwater for human activities.
In conclusion, the final answer is that approximately 30% of the earth's freshwater is groundwater. This calculation takes into consideration the percentage of groundwater in relation to the earth's total freshwater resources. However, in terms of the earth's total water resources, groundwater makes up only 0.0006%. This highlights the importance of preserving and managing groundwater resources for sustainable use, thus the correct option is c.