Pop Quiz:

In the U.S., 12 states use 50% of all water used nationally in a year. Which state is not one of the 12?

A) Iowa B) Arkansas C) Michigan

Answer: A) Iowa. Colorado is among the 12 states that use 50 percent of all water in the U.S. alongside California, Texas, Idaho, Florida, Arkansas, New York, Illinois, North Carolina, Michigan, Montana, and Nebraska.

Water Use in the U.S. is at the Lowest Level Since 1970

It turns out your efforts to take shorter showers and convert to low flush toilets are actually making a difference. A survey conducted by the U.S. Geological Survey (USGS) found that water use in the U.S. is at its lowest level since 1970, largely because of reductions in water withdrawals for public supply.

The USGS has been conducting a series of water use studies every five years since 1950. In 2015, 322 billion gallons of water per day were withdrawn for use, a nine percent decrease from 2010. The decrease is more heartening when considered alongside the four percent population increase during that time. The 2015 measures are the lowest recorded since 1970, when withdrawals were 370 billions of gallons a day.

Tim Petty, assistant secretary for Water and Science at the Department of the Interior, said, "The downward trend in water use shows a continued effort towards efficient use of critical water resources, which is encouraging.”

Public supply use has fallen significantly, dropping from 88 gallons per capita per day in 2010 to 82 gallons in 2015. This is part of a larger per capita downward trend in public supply since 1980, when usage was 112 gallons per capita per day.

Thermoelectric water withdrawals, used to run thermal power stations, remain the largest user of water in the U.S. Fortunately, increased efficiency in thermoelectric plants have led to an 18 percent decrease in water use since 2010. So, thermoelectric water use joins public supply in reaching near-1970 levels.

Public supply, thermoelectric, and crop irrigation make up 90 percent of all water use in the U.S.

And while overall water use is down, some types of water use are up. Crop irrigation water withdrawals have increased two percent since 2010. Unsurprisingly, California was the biggest consumer of water for irrigation in 2015. The multi-year drought the region experienced during the time of the study likely impacted the state’s use of nine percent of all water withdrawals in the country. California, along with the 11 other states of Texas, Idaho, Florida, Arkansas, New York, Illinois, Colorado, North Carolina, Michigan, Montana, and Nebraska, accounts for 50 percent of total water usage in the U.S.

The USGS has created an interactive map along with additional charts and graphs to visually represent how water is used in the U.S..