The lake's waters were impounded by the Copco Number 1 Dam, which was completed in 1922 as part of the Klamath River Hydroelectric Project.

The lake was expected to take three to four weeks to fully drain, at which point crews will plant native vegetation along the emerged riverbank.

[16] In the summer months, the lake often experienced large blooms of toxic cyanobacteria rendering the water unsafe for human contact or consumption.

The dam diverted most of the flow of the river, about 2,400 to 2,500 cu ft/s (68 to 71 m3/s), through a flume and tunnels to a 27-megawatt powerhouse 1.5 miles (2.4 km) downstream, on the upstream end of Iron Gate Reservoir.

The diversion bypassed a canyon section of the Klamath River that historically consisted of some steep rapids.

The dam was required to maintain a minimum release of 10 cu ft/s (0.28 m3/s) to prevent this stretch from being entirely dewatered.