California Water Science Center


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 in the Nation are droughts or very low flows occurring now? How can I see these sites on a map and get to the data?

To view the USGS streamflow information on drought, see the drought map on our WaterWatch site, which shows below-normal, 7-day average streamflow compared to historical streamflow for the United States. Links to additional maps and drought data are listed on our Drought website and the U.S. Drought Portal .

Why doesn't a drought end when it rains?

Rainfall in any form will provide some drought relief. A good analogy might be how medicine and illness relate to each other. A single dose of medicine can alleviate symptoms of illness, but it usually takes a sustained program of medication to cure an illness. Likewise, a single rainstorm will not break the drought, but it might provide temporary...

What is an invasive species and why are they a problem?

An invasive species is an introduced, nonnative organism (disease, parasite, plant, or animal) that begins to spread or expand its range from the site of its original introduction and that has the potential to cause harm to the environment, the economy, or to human health. A few well-known examples include the unintentional introduction of the...

What are zebra mussels and why should we care about them?

Zebra mussels are an invasive, fingernail-sized mollusk that is native to fresh waters in Eurasia. Their name comes from the dark, zig-zagged stripes on each shell. Zebra mussels probably arrived in the Great Lakes in the 1980s via ballast water that was discharged by large ships from Europe. They have spread rapidly throughout the Great Lakes...

How can the spread of zebra mussels be prevented?

The USGS documents the zebra mussel's geographic distribution and studies its behavior and biology. The resulting information is critical in helping to develop strategies aimed at containing and controlling the mussel's spread. Meanwhile, catching and transporting zebra mussels for use as bait, food, and aquarium pets is highly discouraged. We...