Introduction to the Farmers Screen
The Farmers Screen is a horizontal, flat-plate fish and debris screen. Designed to be installed in an off-stream channel, water, fish, and debris pass quickly over the Farmers Screen and return to the river. Inside the screen, the actual screening material lies parallel to the water’s surface. Diverted water travels slowly through the screen material while the water carrying fish and debris moves quickly across the screen surface, cleaning it as it returns to the river. This combination of minimal downward velocity and high sweeping velocity is what manages debris and protects fish. Finally, the taper and weir walls ensure uniform water depths and velocities.
The Farmers Screen is different from traditional screening technologies in several ways. First, the screen material itself is horizontal as opposed to vertical, allowing debris and fish to be carried above and over the surface of the screen material. Second, the Farmers Screen has no moving parts, eliminating the need for a power supply and greatly reducing the maintenance associated with the screen. Third, the Farmers Screen is substantially self cleaning, meaning that under normal operating conditions the screen will not accumulate debris on the screen surface which again reduces maintenance requirements and provides consistent fish protection. Finally, to operate correctly, the Farmers Screen requires by-pass flow, which provides protection from both injury and delay for fish as well as effective debris management.
The Farmers Screen design has been successfully implemented at 24 points of diversion in 4 states thus far (Oregon, Idaho, Montana, and Wyoming). These sites span a wide range of flows (from 0.5 CFS maximum to 160 CFS maximum) and site conditions. All of the installed Farmers Screens are located off-channel and behind a functioning head gate that controls the rate of flow into the screen system.
The Farmers Screen received federal approval in 2011 from the National Marine Fisheries Service (NMFS), and is marketed by the nonprofit Farmers Conservation Alliance (FCA), based in Hood River.
To date, Farmers Screen installations have converted a total of 484.2 cubic feet per second of diverted water to fish-friendly diversions, while opening 167.70 river miles for fish passage. These Farmers Screens have saved their owners of $493,700 a year in avoided operation and maintenance costs. A total of 10 MWh of fish-friendly hydropower generation capacity has been optimized.