Temperature and Algae Curtain

Iron Gate Dam is an earthfill hydroelectric dam on the Klamath River in northern California. On April 7, 2020 the California State Water Resources Control Board issued a Clean Water Act certification and environmental assessment for the proposal to remove dams around Copco Lake and Iron Gate Reservoir, "another hurdle that moves the prospect of re-opening 360 miles of the Klamath River and its tributaries to imperiled salmon closer to reality".

In 2015 PNP was contracted by PacifiCorp to help reduce the impact of their hydroelectric dams, particularly on migratory fish such as salmon and steelhead trout. In order to achieve its goals, the company needed to control algae growth in reservoirs and contain higher temperature lake water in the reservoir while releasing cooler, deeper lake water downstream.

PNP's manufactured a temperature and algae curtain, which was designed to isolate and segregate the shallow and deep waters upstream of the curtain, so the water conditions downstream of the dam could be similar to deep-water conditions upstream of the curtain. This curtain was designed in a way to assist in studies of its effectiveness. Watercourse Engineering, Davis California, compared data which included thermograph array data, Cyanobacteria, and microcystin levels and found that downstream of the dam and curtain, there was less temperature stratification and the temperature and Microcystin levels closely matched those found in the deeper waters of the reservoir upstream of the curtain.

The curtain consisted of a PNP MultiFunction Boom™, large mesh netting that provided strength, shape, and support, and a non-permeable fabric barrier to restrain water. Winches on the boom allowed the non-permeable barrier to be raised or lowered by operators, as needed for testing and operational outcomes. The large mesh was chosen to reduce drag, possible fouling, and allow fish to pass below the curtain. The expected life of the curtain is 10 years, and 25 years for the floating structure.


  •  Designed to control algae and temperature
  •  800 ft long x 40 ft deep
  •  6” heavy netting support exclusion net
  •  XR5 non-permeable fabric curtain
  •  Operator controlled surface winch system
  •  Adjustable depth to 40 ft
  •  Deployed year-round