California Water Science Center

FAQ

If you don't see your question below, please let us know and we'll be happy to help.

Current and historical streamflow, groundwater, and water quality data can be found at the National Water Information System (NWIS) site. To search geographically, use the NWIS Mapper feature.

The California Department of Water Resources is the official source of well completion reports.

Where can I find information about my local drinking water supply?

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...

Where can I get my well water tested?

Contact your county or state health department or check with your State Certification Officer for a list of state certified laboratories in your area that do water testing. The cost will vary, depending on the laboratory and the test(s), but people usually consider the cost to be reasonable. Also try using your browser's search engine to do a...

Where can I get real-time and historical streamflow information?

The best starting point for USGS streamflow data is the interactive National Water Information System (NWIS): Mapper website. Zoom in to your area of interest or use the search options in the left navigation window. The map displays active surface-water sites by default, but you can change the type of water site (surface-water, groundwater,...

How often are real-time streamflow data updated?

USGS real-time streamflow data are typically recorded at 15-minute intervals, stored onsite, and then transmitted to USGS offices once every hour, depending on the data relay technique used. Recording and transmission times might be more frequent during critical events (floods, for example). Data from current sites are relayed to USGS offices via...

How can I find the depth to the water table in a specific location?

The depth to the water table can change (rise or fall) depending on the time of year. During the late winter and spring when accumulated snow starts to melt and spring rainfall is plentiful, water on the surface infiltrates into the ground and the water table rises. When water-loving plants start to grow again in the spring and precipitation gives...

Where can I find flood maps?

FEMA is the official public source for flood maps for insurance purposes: FEMA’s Flood Map Service Center FEMA’s Flood Hazard Map FAQs NOAA is responsible for producing flood forecast maps that combine precipitation data with USGS streamflow data: National Flood Forecasts Interactive Flood Information Map Coastal Inundation Dashboard : Real-time...

How do we benefit from USGS streamgages?

Information on the flow of rivers is a vital national asset that safeguards lives, protects property, and ensures adequate water supplies for the future. The USGS is the federal agency responsible for operating a network of about 7,000 streamgages nationwide. Data from this network are used by water managers, emergency responders, utilities,...

Does "stage" tell you how much water is flowing in a stream?

Not directly. You cannot say that because a stream rises (doubles) from a 10-foot stage to a 20-foot stage that the amount of flowing water also doubles. Think of a cereal bowl with a rounded bottom. Pour one inch of milk in it. It doesn't take much milk to make it up to the one inch level because the bowl is at its narrowest near the bottom. Now...

How important is groundwater?

Groundwater, which is in aquifers below the surface of the Earth, is one of the Nation's most important natural resources. Groundwater is the source of about 37 percent of the water that county and city water departments supply to households and businesses (public supply). It provides drinking water for more than 90 percent of the rural population...

What determines if a well will go dry?

A well is said to have gone dry when water levels drop below a pump intake. This does not mean that a dry well will never have water in it again, as the water level may come back through time as recharge increases. The water level in a well depends on a number of things, such as the depth of the well, the type (confined or unconfined) of aquifer...

How can an earthquake affect groundwater or changes in wells?

Groundwater levels in wells may oscillate up and down while seismic waves pass, and in some cases, the water level may remain higher or lower for a period of time after the seismic wavetrain has ended. Learn more: Groundwater Effects from Earthquakes Groundwater Response to Earthquakes

Can hydraulic fracturing impact the quality of groundwater or surface water?

Conducted properly, hydraulic fracturing (or “fracking”) has little possibility of contaminating water supplies. Properly constructed wells prevent drilling fluids, hydraulic fracturing fluids, deep saline formation waters, or oil and gas from entering aquifers. Carefully constructed and operated well sites have the ability to contain potential...

Does the use of pesticides affect our Nation's water quality?

Pesticide use in the United States has increased because not only must we supply our exploding population with food, but crops and food are also grown for export to other countries. The United States has become the largest producer of food products in the world, partly owing to our use of modern chemicals (pesticides) to control the insects, weeds...

Why are some lakes full of algae and thick plants?

Plants naturally grow in and around lakes, but sometimes lakes and ponds can get an overgrowth of plants, algae, or bacteria. In many cases, humans are responsible. Chemicals that are used on lawns and in agriculture (like nitrogen and potassium) wash into our water systems. Once there, plants and algae have a feast on this “food”. Sometimes...

How are floods predicted?

Flood predictions require several types of data: The amount of rainfall occurring on a real-time basis. The rate of change in river stage on a real-time basis, which can help indicate the severity and immediacy of the threat. Knowledge about the type of storm producing the moisture, such as duration, intensity and areal extent, which can be...

What are the two types of floods?

There are two basic types of floods: flash floods and the more widespread river floods. Flash floods generally cause greater loss of life and river floods generally cause greater loss of property. A flash flood occurs when runoff from excessive rainfall causes a rapid rise in the water height (stage) of a stream or normally-dry channel. Flash...

Will global warming produce more frequent and more intense wildfires?

There isn’t a direct relationship between climate change and fire, but researchers have found strong correlations between warm summer temperatures and large fire years, so there is general consensus that fire occurrence will increase with climate change. Hot, dry conditions, however, do not automatically mean fire—something needs to create the...

What should I know about wildfires and debris flows?

Wildland fires are inevitable in the western United States. Expansion of human development into forested areas has created a situation where wildfires can adversely affect lives and property, as can the flooding and landslides that occur in the aftermath of the fires. There is a need to develop tools and methods to identify and quantify the...

What causes drought?

A drought is a period of drier-than-normal conditions that results in water-related problems. The amount of precipitation at a particular location varies from year to year, but over a period of years, the average amount is fairly constant. In the deserts of the Southwest, the average precipitation is less than 3 inches per year. In contrast, the...

When does a drought begin and end?

The beginning of a drought is difficult to determine. Several weeks, months, or even years might pass before people know that a drought is occurring. The end of a drought can occur as gradually as it began. The first evidence of drought is usually seen in records of rainfall. Within a short period of time, the amount of moisture in soils can begin...