Let's assume that five gallons represent all the water on Earth. In reality, Earth's total water supply is estimated to be about 332,500,000 cubic miles (mi³), which is an enormous volume.
For the sake of simplification, let's work with the given representation of five gallons and calculate how much water would be available for human consumption. Firstly, we need to understand that not all water on Earth is accessible or suitable for human consumption. The majority of Earth's water (about 97.5%) is saltwater found in the oceans, and it is not directly drinkable without desalination.
Only a small fraction of Earth's water (approximately 2.5%) is freshwater, and most of that freshwater is locked up in ice caps, glaciers, and groundwater. A small percentage of freshwater is found in surface water bodies like lakes, rivers, and streams.
For the sake of this calculation, let's assume that all of Earth's freshwater is available for human consumption, even though much of it is not readily accessible due to location or contamination.
According to the United States Geological Survey (USGS), the estimated volume of all freshwater on Earth is about 2.5 million mi³.
Now, we need to convert the given five gallons to cubic miles to determine the proportion of available freshwater compared to the total water on Earth:
1 gallon ≈ 3.78541 x 10^-8 cubic miles
So, 5 gallons ≈ 5 x 3.78541 x 10^-8 cubic miles ≈ 1.892705 x 10^-7 cubic miles.
To find the proportion of available freshwater for human consumption:
Proportion = (Volume of freshwater / Total water volume) x 100 Proportion = (2.5 million mi³ / 332,500,000 mi³) x 100 Proportion ≈ 0.75%
Thus, if five gallons represent all the water on Earth, approximately 0.75% of that volume (about 1.89 x 10^-7 cubic miles) would represent the available freshwater for human consumption. This is an incredibly small fraction of the total water on Earth, emphasizing the importance of responsible water usage and conservation.