Final answer:
Approximately 21% of the USA's total drinking water is supplied by groundwater.
Step-by-step explanation:
Groundwater is an important source of drinking water in the United States, with millions of Americans relying on it for their daily water needs. In fact, according to the United States Geological Survey (USGS), groundwater accounts for approximately 21% of the total drinking water supply in the country. This percentage may seem relatively small compared to other sources such as surface water, which accounts for 79% of the total drinking water supply, but it is still a significant contribution to the nation's water needs.
To understand how this percentage is calculated, we must first define what is meant by groundwater. Groundwater refers to water that is stored underground in the spaces between soil particles, rocks, and other materials. This water is replenished through natural processes such as precipitation and runoff. Groundwater can be accessed through wells and pumped to the surface for various uses, including drinking water.
To calculate the percentage of the USA's total drinking water supplied by groundwater, we must first determine the total amount of drinking water used in the country. According to the USGS, the total water use for public supply, domestic, and commercial purposes in the United States in 2015 was approximately 322 billion gallons per day (bgd). From this total, we can subtract the amount of water supplied by surface water sources, which is about 255 bgd, leaving us with 67 bgd of groundwater used for drinking purposes.
Next, we can calculate the percentage by dividing the amount of groundwater used for drinking (67 bgd) by the total amount of drinking water used (322 bgd) and multiplying by 100. This gives us a percentage of approximately 20.8%, which rounds up to 21%.
It is important to note that this percentage may vary depending on the region and the specific sources of drinking water available. Some areas may rely more heavily on groundwater, while others may have more access to surface water sources. Additionally, this percentage may also change over time as population growth and changes in water use patterns impact the demand for drinking water.
In conclusion, approximately 21% of the USA's total drinking water is supplied by groundwater. This highlights the importance of managing and protecting groundwater resources to ensure a reliable and safe supply of drinking water for current and future generations.