Environmental

Lake Oroville full, but drought conditions not forgotten

Lake Oroville full, but drought conditions not forgotten
(An aerial overview of the recently completed Lake Oroville main spillway during Phase 2 of the recovery efforts. Work continues on the concrete cap below the Lake Oroville emergency spillway weir at the Butte County, California site. Photo taken January 24, 2019. Kelly M. Grow / California Department of Water Resources, FOR EDITORIAL USE ONLY)

In its weekly Lake Oroville update, the California Department of Water Resources reported that the lake remains at full capacity, and windy periods might cause water to splash onto and over the crest of the emergency spillway, but all this water may be needed if the state returns to drought conditions.

DWR said it is adjusting water releases from the reservoir as needed to account for increasing or decreasing inflows while maintaining flood protection for downstream communities. Releases are closely coordinated with the U.S. Army Corps of Engineers and other water operators and adjusted as needed to maintain balance throughout the water system. DWR continues to monitor Lake Oroville levels to optimize water storage while meeting environmental requirements and allowing for carryover storage into next year. 

Oroville Reservoir Level is at 899 feet elevation and current storage capacity is about 3.53 million acre-feet (maf), which is 100% of its total capacity and 127 %of the historical average. Total releases to the Feather River are 3,800 cubic feet per second (cfs), with 850 cfs being routed down the Low Flow Channel through the city of Oroville and an additional 2,950 cfs being released from the Thermality Afterbay River Outlet 5 miles downstream from Oroville.

The State Water Project (SWP) provides water to 29 public water agencies and also uses the water for hydropower generation. The SWP is a system of 32 storage facilities, 21 pumping plants, four pumping-generating plants, eight conventional hydroelectric plants and about 700 miles of canals and pipelines. Lake Oroville is the largest storage facility in the SWP, providing water to 27 million Californians and 750,000 acres of farmland, while providing flood protection to downstream communities along with environmental and recreation benefits. Among the SWP generating plants is the 762 MW Hyatt Powerplant at the foot of Oroville Dam.

Spring is an important time for water project operators to fill reservoirs like Lake Oroville ahead of dry months. It also is an important migration window for many native fish species. DWR said it is using the best available science to protect fish species. However, SWP operations have faced significant restrictions in the Delta this year that have impacted the ability in other areas of the state to capture and store the water needed if California sees a return to drought conditions.