MARYSVILLE, Calif. (Sept. 25, 2025) – Yuba Water Agency will increase flows on the Yuba River between New Bullards Bar Dam and New Colgate Powerhouse starting Monday, Sept. 29 as it begins its months-long Colgate Tunnel and Penstock Improvement Project.
“This will be a significant change in conditions for this stretch of the river,” said Yuba Water Operations Manager Karl Parker. “While these flows are typical for the river below Colgate, they’ll now be flowing above Colgate since we’ll be taking our powerhouse offline. These flows will be higher than normal for this time of year, and we encourage local recreators to avoid this section during the increase or – at a minimum – use extreme caution.”
Typical flows in this section of the river during late September are between 6 and 40 cubic feet per second. Starting Monday, flows upstream of Colgate will increase to approximately 900 cubic feet per second. One cubic foot of water is about the volume of a basketball.
These flows will continue through February 2026 while Yuba Water makes improvements to the five-mile-long rock tunnel and one-mile-long penstock that move water from New Bullards Bar Reservoir to New Colgate Powerhouse for hydropower generation. This major maintenance is infrequent, but essential to ensure the longevity of the tunnel and the reliability of Yuba Water’s hydropower operations.
Visit yubawater.org for the latest river conditions and engage.yubawater.org/colgate-tunnel for more information on the Colgate Tunnel and Penstock Improvement Project.