The considerations shown below are intended to guide initial site assessment. Local fish passage regulations and the specific nature of the host stream will guide a final screen design, along with other site-specific requirements.
- The proposed site must be located off-channel and ﬂow to the screen controlled with a properly functioning head gate.
- There must be sufficient flow entering the screen to ensure 5 to 10% of the diversion is returned to stream as bypass ﬂow.
- Water at the leading edge of screen must be steadily and uniformly ﬂowing at 1 to 2 meters per second. A straight ﬂume ﬁve times longer than the width of the screen’s leading edge will generally create this even ﬂow.
- A drop in water surface elevation of 15 to 30 centimeters is needed between the ﬂume and the exit of the screened ﬂow.
- The host stream must not back up the fish return.
- The screen area can be estimated as 20 square meters for every cubic meters per second of ﬂow. The footprint of the structure is typically twice that. The length to width ratio of this footprint varies significantly.