The USGS Water Science School
Water Science water-use pages
Categories of Use:
National Water Use Program
Information and Data
Public-supply water use
No doubt the first public-supply water system was when Jack the Caveman was hired by his neighbors to fetch a bucket of water from Dinosaur River in exchange for some delicious prehistoric bran muffins. If you read our fictional tale about starting a new town in the desert, you'll see that even in a town with a population of one person, a plan to get, use, and dispose of water is always needed. Public and private water-supply organizations that get water, clean it and deliver it to local residents exist anywhere people exist.
Public water-supply systems, which you might know better as the county and city water departments, are vitally important to all populations. These are government or privately-run facilities that withdraw water from rivers, lakes, reservoirs, and wells and then deliver it to our homes, businesses, and schools. The majority of the population (about 86 percent) of the United States nowadays gets their water in this manner. You probably get your home drinking water this way. In the past, when the population was a lot more rural, people used to have to dig their own wells and create storage tanks for their water supply. But with large numbers of people living in bigger cities the public-supply systems do that work for us. All we do is turn on the tap ...oh, and pay the bills.
For this site, public supply refers to water withdrawn by public and private water suppliers that provide water to at least 25 people or have a minimum of 15 connections. Public-supply water is delivered to users for domestic, commercial, and industrial purposes, and also is used for public services and system losses.
Public-supply withdrawals for the Nation, 2010
Approximately 42,000 Mgal/d, or 47,100 thousand acre-ft/yr, of water were withdrawn for public supply in 2010. This amount is 5 percent less than the estimated amount of water withdrawn for public supply in 2005. Public supply represents about 14 percent of total freshwater withdrawals and 22 percent of all withdrawals excluding thermoelectric power. In some States, public-supply water sources include desalinated seawater or brackish groundwater that has been treated to reduce dissolved solids. A combined total of 23.5 Mgal/d saline surface-water withdrawals for public-supply use were reported in Florida, the U.S. Virgin Islands, Massachusetts, and Texas. A combined total of 317 Mgal/d saline groundwater withdrawals for public-supply use were identified in Florida, California, Texas, Virginia, and Utah. Because these saline withdrawals were identified for only seven States and represent less than 1 percent of total public-supply withdrawals, they are not listed separately in table 5 but were included in the calculations.
Public-supply withdrawals, by State, 2010
As time has gone by, more and more people have been served by the Nation's water departments. In 2010, about 268 million people of the Nation's total population of about 313 million were served in this manner. The map below shows the amount of public-supply withdrawals by State for 2010.
An estimated 268 million people relied on public-supply water for their household use in 2010. This number represents about 86 percent of the total U.S. population. About 35 percent of all public-supply withdrawals were in the four States with the largest populations: California, Texas, New York, and Florida. Sixty-three percent of water withdrawn for public supply in 2010 was from surface sources, such as lakes and streams; the other 37 percent was from groundwater.
Five States—California, Texas, New York, Pennsylvania, and Illinois—each withdrew more than 1,000 Mgal/d of surface water for public supply in 2010 and together accounted for 40 percent of the total surface-water withdrawals for public supply. In 36 States, including Puerto Rico and the U.S. Virgin Islands, surface-water sources provided more than half of the total public-supply withdrawals.
Three States — California, Florida, and Texas — each withdrew more than 1,000 Mgal/d of groundwater for public supply in 2010 and accounted for 38 percent of total groundwater withdrawals for public supply. States that relied on groundwater for 75 percent or more of their public-supply withdrawals were Hawaii, Florida, Idaho, Mississippi, Nebraska, and Iowa.
Trends in public-supply water withdrawals, 1950-2010
Public-supply withdrawals in 2010 were 5 percent less than in 2005, decreasing from 44.3 Bgal/d to 42.0 Bgal/d and marking the first decline since public-supply withdrawals were initially reported in 1950. Total public-supply withdrawals in 2010 were at levels not reported since prior to 2000. During decadal periods between 1950 and 1960, public-supply withdrawals increased 50 percent in conjunction with the high population growth rates during those periods. Percentage increases in public-supply withdrawals during the next three decadal periods between 1960 and 1990 averaged 23 percent, again coinciding with the rate of growth in population during the same time periods. Between 1990 and 2000, the rate of increase in public-supply withdrawals was lower at 12 percent. Between 1990 and 2010, public-supply withdrawals have been roughly 60 percent from surface water and 40 percent from groundwater sources. The percentage of the population that is served from public-supply withdrawals has increased from 62 percent in 1950 to 86 percent in 2010.
Since the end of World War II there has been a trend of people moving out of the rural countryside and into the ever-expanding cities. This has important implications for our water resources. Communities have had to start building large water-supply systems to deliver water to new populations and industries.
In times past, when most people lived in rural areas, they had to find ways to supply their own water—often by drilling a well and pumping water to their homes. Not many city dwellers have a well in their backyards today. A public-water supply system, such as your local water department, nowadays delivers water to most homes. The bar chart below shows the trend toward urbanization over the last 50 years. Notice how the blue bars (representing the millions of people served by a public water-supply system) keeps going up while the green bars (representing the number of people who supply their own water) has trended downward, with 14 percent of the Nation's population supplying their own water in 2005.
Data for freshwater withdrawals for 1980-2000 have been revised from original published values.
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