Smith-Root

What Does A Smith-Root Electric Barrier or Guidance System Do?

Each barrier/guidance system is designed and operated to change an animal’s behavior. While most of our systems have been installed to block fish movement totally, we have also installed systems where the objective is to guide fish towards a specific location (e.g., adult Pacific salmon across a stream towards the entrance to a fish ladder).

Electric barriers are used for control of invasive species, for clearing fish from turbine raceways and intakes, and for collecting runs to allow separating of fish species. They can also be calibrated to sort large fish from small. Since some species are less affected by electric fields, they can perform as filters.

Other unique applications have included:

We are continually looking for locations and partners to improve our ability to stop and/or guide fishes.

What Does A System Look Like?

While each application is designed to achieve a specific barrier/guidance objective, a system generally consists of a series of electrodes (cables or metal bars) attached to the bottom of the channel, often in grooves in a concrete sill, rising up the sides of the channel to accommodate higher water levels. An example of a fairly typical system (Eagle Creek National Fish Hatchery, OR) is shown in Photo 6. However there are many other types of configurations that our engineers can design, including vertical pile-mounted and suspended vertical electrodes. Different configurations produce different fields, some uniform, some graduated, some more intense close to the bottom.

Eagle Creek is a good example of a stream-deployed barrier. The upstream length of a barrier can be increased to accommodate greater water depths and river commerce, such as barges. Other design factors are the water conductivity (water conductivity of 5,000 µS/cm or about 3.9 parts per thousand salinity, or less, can be electrified with reasonable power consumption), and the hydraulics of water flow at the site.

A big advantage of an electric barrier or guidance system is that there need be no physical structure in the water column, as opposed to a screen, fence, or weir. Therefore, our barriers are not subject to debris clogging or physical damage and water traffic may pass unobstructed.

Each site is unique in terms of its channel geometry, electrical field characteristics, and overall objective. Smith-Root has the experience and technical staff to design and install a system that is suitable for your needs.

How Does Our System Work?

A typical barrier/guidance system produces a graduated, pulsed field of direct current (DC) in the water that affects muscular control in fish, or sensory organs (whiskers) in marine mammals. The animal feels uncomfortable in the field and moves in the direction that reduces the discomfort. The driving electric voltage comes from a Smith-Root pulse generator unit. A graduated field can be specifically designed to meet the needs of each site in terms of its physical configuration, water depth and conductivity, the size and species of fish for which behavior modifications are required to be changed, and the client’s objective (i.e., total blocking, guidance of adults, barrier to adults only, etc.).

Fields are mathematically modeled by Smith-Root to assist in their design and to provide a basis for calibration on site. Fields are represented as voltage gradients (V/cm). A fish within a field feels a voltage head-to-tail equal to the voltage gradient multiplied by the fish length. The total voltage from one end of the field to the other is not relevant to fish behavior.

While barriers to upstream-migrating fish can be set high to disable temporarily any fish that challenge them (since disabled fish will be swept downstream), barriers to downstream-migrating fish have to be designed carefully to balance the electrical field and the water velocity patterns so that fish are repelled before they become disoriented.