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January 4, 2023

U.S. Geological Survey field crews measured high streamflows this week throughout California, thirteen of which were record high-flow measurements.

water crashing over a dam spillway
High flows at streamgage 11172945 (Alameda Creek above Div Dam near Sunol, California) were captured by USGS hydrologic technician Louis Cannarozzi on 12/31/2022. Heavy precipitation caused higher-than-normal streamflow in many areas as an atmospheric river moved through northern California.

These measurements provide information that protect life, property, and the environment including uses for water supply and management, monitoring floods and droughts, bridge and road design, determination of flood risk and many recreational activities 

A man is measuring streamflow using a truck mounted boom and price AA meter suspended off a bridge over high streamflow in the Cosumnes River below
USGS hydrologic technician Travis Hiett measures streamflow using a truck mounted boom and price AA meter at the Cosumnes River at Michigan Bar, California on December 31, 2022. Travis captured the highest direct measurement ever recorded at this site—63,700 cubic feet per second—in over 100 years of record. For site data, please visit https://waterdata.usgs.gov/monitoring-location/11335000/.

“Heavy rains and hazardous weather conditions continue in northern California this week,” said Mark Dickman, Associate Director of Data for the USGS California Water Science Center. “Streamflows have been very high, and we expect more over parts of the region the next several days.” 

USGS crews made 77 streamflow measurements at 58 streamgages between December 31, 2022 and January 2, 2023, and recorded 13 preliminary record-high streamflow measurements in northern California. To the east of Sacramento, crews captured the highest direct measurement ever recorded at streamgage 11335000 on the Cosumnes River near Michigan Bar, CA—63,700 cubic feet per second—in over 100 years of record. Additional historic peaks are expected throughout the state this week, as another atmospheric river is likely to occur.  

a river with high streamflow taken from a bridge. Green grass and vegetation can be seen on both banks
The Consumes River experienced record streamflow over the 2022 New Year's holiday weekend as an atmospheric river moved through northern California.  Crews captured the highest direct measurement ever recorded at this site—63,700 cubic feet per second—in over 100 years of record. (Credit: Susan Brockner, USGS. Public domain.) 

These data are used by the National Weather Service to develop flood forecasts, the U.S. Army Corps of Engineers to manage flood control and local agencies in their flood response activities.  

“The SFPUC relies on accurate and real-time hydrology information for our water supply system and watershed land operations, particularly during storm events,” said Tim Ramirez with the San Francisco Public Utilities Commission, “Information regarding reservoir levels, and streams flowing into and from the reservoirs are critical data we use to make operational decisions, and we are grateful for the USGS staff out in the field during these storm events who are an important part of our team.” 

There are 458 USGS-operated streamgages in California that measure water levels, streamflow, and rainfall automatically and send data wirelessly, which are accessible from the National Water Dashboard. When flooding occurs, USGS crews make numerous streamflow measurements to verify the data that the USGS provides to federal, state, and local agencies, as well as to the public. 

For more than 125 years, the USGS has monitored flow in selected streams and rivers across the United States.  

Access current flood and high flow conditions across the country by visiting the USGS National Water Dashboard. Receive instant, customized updates about water conditions in your area via text message or email by signing up for USGS WaterAlert

Map of California with circles of varying size depicting streamflow measurements. Bigger circles mean higher flow.
At atmospheric river brought heavy precipitation to California from December 31, 2022 through January 2, 2023.  USGS crews took 77 measurements at 58 sites across the state, with northern California being hardest hit.  This map shows where some of the highest streamflow occurred.  Data are provisional and subject to revision.
woman taking measurements at stream gage
Sharon Mulready, USGS Hydrologic Technician, recording the high-water mark on gage 11161000 San Lorenzo River Santa Cruz. The stream is filled with a tremendous amount of sediment moved by the storm on December 31st, 2022. The sediment displaced the flow of the stream about 60 feet away.