Double rainbow – where does it lead?

Rainbow and Hydropower

Always on a mission to capture the diverse and unusual impressions afforded by our work, we recently witnessed this beautiful double rainbow — which appeared to end at the Colgate Powerhouse on the Yuba River. Unlike most hydroelectric generators, which are usually located at the base of dams, Colgate Powerhouse is some distance downstream of its water supply. Water arrives here via 26-foot diameter pipes from New Bullards Bar Reservoir, about five miles away. Although flood protection is the primary purpose of the reservoir, the powerhouse provides a supercharged bonus: the elevation difference between New Bullards Bar Dam and the powerhouse creates enough hydraulic head, or liquid pressure, to turn the facility’s 18-foot Pelton wheels (the largest turbine of its kind in existence) at 180 revolutions per minute and generate up to 315 MW of electricity—enough to supply a city of 350,000 people.

The large volumes of water that re-enter the river below hydroelectric facilities as a result of operational changes often create treacherous, drastically fluctuating riverine conditions. Close coordination with facility operators is therefore essential to successfully implement projects and ensure safe working conditions downstream of a powerhouse.