PROJECT ALERT NOTICE (CA) California experiencing a wave of AR storms—Continued, Day 6

Date: Mon, 09 Jan 2017 15:34:37 EST

Summary: Multiple atmospheric rivers continue to bring heavy rainfall and snow to many parts of California this week.

Today, nearly all of California will experience light to moderate rainfall, with snow accumulations at higher elevations. Precipitation is expected to continue across the region through the end of week, with the heaviest precipitation expected on Tuesday. This precipitation, which adds to previous accumulations of rain and snow from last week’s storms, will increase the potential for flash floods, landslides, and avalanches. Currently, streamflow at numerous sites across the State are above the 95th percentile, with many of those streams predicted to peak and exceed flood or monitor stage today and on Wednesday.

Precipitation reports from the Center for Western Weather and Water Extremes show many parts of central California received as much as 12 inches during the past 72-hours, with some parts receiving as much as 16 inches during the past 72-hours. Reservoir levels in California are rising, proving much needed water reserves to reservoir supplies that have experienced record lows levels in recent drought years. For example, the water levels in Don Pedro Reservoir, which is located on the Tuolumne River in the foothills of the Sierra Nevada and is part of the Hetch Hetchy Project that provides water supply to San Francisco, increased over 7 feet yesterday during a 24-hour period.

The California Water Science Center (CAWSC) currently has 27 crews responding to this event from all field office, except the Poway Office in southern CA. Crews from USGS field offices in the following service areas are deployed for flood response: Ukiah, CA (3); Redding, CA (2); Eureka, CA (1); Santa Cruz, CA (5); Truckee, CA (3); Redlands, CA (3); and Sacramento, CA (5). More crews are planned to deploy over the next few days as this storm continues to bring precipitation that will result in flood conditions and record high streamflow not seen in several years. Forecasters from the National Weather Service estimate this storm to be a ten-year event for California.

CAWSC managers are in contact with water resource managers from the Bureau of Reclamation, the Army Corps of Engineers, and the National Park Service to coordinate USGS sampling or high-water measurements with planned flood releases. Today, USGS crews are collecting sediment samples and measuring streamflow on the San Joaquin River below Friant Dam (11251000), and on Rio Hondo below Whittier Narrows Dam (11102300) as part of a coordinated effort to collect data during flood releases. A media events is planned for today at the USGS streamgage location below Friant Dam, a streamflow site with significance to the San Juan River Restoration Project

As of yesterday, the CAWSC has collected over 120 streamflow measurements in response to this atmospheric flood event that began on Wednesday January 4, 2017. Yesterday, record streamflow measurements were made at sites 11480390, Mad River above Ruth Reservoir near Forest Glen, CA (5,640 cfs) and 11453500, Putah Creek near Guenoc, CA (23,100 cfs).

Several gages in California experienced damage or interruptions in data transmissions yesterday. For example, streamflow recorded at the 11473900 Middle Fork Eel River near Dos Rios, CA was over 40,000 cfs (26 times greater than the median daily discharge) yesterday just before the orifice was damaged. At another site yesterday in Lake County, CA (11451100, North Fork Cache Creek at Hough Spring near Clearlake Oaks, CA) the streamflow recorded was 50 times greater than the median discharge before data transmissions were interrupted. Other USGS streamflow sites with data issues include sites in the Sierra Nevada (11278400, 11278000, and 11285500). Questionable data have either been removed from NWISWeb or warning statements have been added to qualify the data.

No safety issues have occurred during this series of storms and all staff have followed USGS field reporting and safety protocols. Updates will continue to be provided during the course of this event.