Frequently Asked Questions

Water

The USGS monitors and studies a wide range of water resources and water conditions, including streamflow, groundwater, water quality, and water use and availability.

Filter Total Items: 55
trees and stream
“Reach” can have slightly different meanings, depending on how it is used. A reach is a section of a stream or river along which similar hydrologic conditions exist, such as discharge, depth, area, and slope. It can also be the length of a stream or river (with varying conditions) between two streamgages, or a length of river for which the...
Water cycle graphic
The water cycle, also known as the hydrologic cycle, describes the continuous movement of water as it makes a circuit from the oceans to the atmosphere to the Earth and on again. Most of Earth's water is in the oceans. The sun, which drives the water cycle, heats water in the oceans. Some of it evaporates as vapor into the air. Rising vapor cools...
Domestic water use, 2010, by State
Since 1950, the USGS has collected and analyzed water-use data for the United States and its Territories. That data is revised every 5 years. As of 2015, the United States uses 322 billion gallons of water per day (Bgal/day). The three largest water-use categories were irrigation (118 Bgal/day), thermoelectric power (133 Bgal/day), and public...
All water on Earth in a sphere, placed over a "dry" globe
Earth is estimated to hold about 1,460,000,000 cubic kilometers of water. The breakdown of where all that water resides is estimated as follows: Oceans (saline) 1,419,120,000 cubic kilometers Ice caps and glaciers (fresh) 31,244,000 cubic kilometers Ground water (fresh and saline) 8,906,000 cubic kilometers Streams and lakes (fresh) 132,860 cubic...
Iron oxide (reddish brown color) is present in cracks in rocks
The brown stain is from a large amount of iron in your water. It is closely related to simple rust that you see on metal, which is iron oxide. Your water probably comes from groundwater that filtered through rocks containing iron-rich minerals on its way to the well.
Glasses of water from a tap showing air bubbles, making the water appear cloudy.
Once in a while you get a glass of water that looks cloudy; maybe milky is a better term. After a few seconds, it miraculously clears up! The cloudiness is due to tiny air bubbles in the water. Like any bubbles, the air rises to the top of the water and goes into the air, clearing up the water. The water in the pipes coming into your house might...
Hard water film on glass and spoon
Water is said to be soft if it has a low concentration of calcium and magnesium ions in it, while hard water has a high concentration of calcium and magnesium. If you use soft water, the ions react with your soap to produce a residue that feels like it is hard to wash off. If you use hard water, you will have a harder time working the soap up into...
Drinking water from tap
The best way to learn about your local drinking water quality is to read the annual drinking water quality report/consumer confidence report that water suppliers now send out by July 1 of each year. The reports are often sent out with water bills, but they may be sent separately. The reports tell where drinking water comes from, what contaminants...
Photo of a young girl drinking water, which likely originated from groundwater sources. 
Bottled water is regulated by the U.S. Food and Drug Administration and by individual states. For general information about bottled water, sources include the International Bottled Water Association and NSF International.
Two USGS National Research Program scientists taking water samples in a wetland.
Naturally-occurring organic compounds are created when plant material decays in lakes and reservoirs. Those organic compounds frequently cause musty, earthy odors, especially toward the end of summer. The odors can be objectionable, but generally are not harmful to health. However, odors can be caused by other constituents as well, so you might...
Image: Natural Iron-rich Acidic Spring Flowing into Cement Creek
Your water might be affected by iron, which is a commonly-occurring constituent of drinking water. Iron tends to add a rusty, reddish-brown (or sometimes yellow) color to water. If the color is more black than red, your water might contain a combination of iron and manganese. Both of these metals can cause staining of plumbing fixtures or laundry...
Image: Ocean and Double Rainbow 2
In the U.S., about 13 percent of all water used is saline water. But saline water can only be used for certain purposes. The main use is for thermoelectric power-plant cooling. About 5 percent of water used for industrial purposes is saline, and about 53 percent of all water used for mining purposes is saline. Saline water can be desalinated for...