The Sunnyside Diversion (Figure 1) is located at river km 167 (river mile 103.8) on the Yakima River. The diversion directs water from the Yakima River into the Sunnyside Canal. Canal operation begins in early March and continues through the irrigation season usually until mid-October. Canal capacity is about 37 m3/s (1300 cfs).

Figure 1. Aerial View of the Sunnyside Dam and Sunnyside Canal Fish Screening Facility

The Sunnyside Screens are located about 0.4 km (0.25 mi) downstream of the headgates of the Sunnyside Canal. The screening facility (Figure 2) diverts fish entering the canal and directs them back to the Yakima River. The trash rack immediately upstream of the Sunnyside Screens "filters" out debris entering the canal. The screening facility houses 17 rotary-drum screens (Figure 2) with axes parallel to the length of the structure. Each screen is about 3.7 m (12 ft) wide and 4.6 m (15 ft) in diameter. Water depth at the screens varies with canal flow. Water depth across the face of the screens at full canal level is normally about 4.3 m (14 ft).

The flow control structure and separation chamber (Figure 2) are located at the downstream end of the screen facility. An intermediate bypass pipe and the terminal bypass, each with a flow of about 1.4 m3/s (50 cfs), feed into the separation chamber. During normal operation, about 2.8 m3/s (100 cfs) of water enters the separation chamber. About 0.6 m3/s (20 cfs) of water, and all the fish in front of the screens, pass through the flow control structure and out the primary fish return pipe. Two bypass water return pumps, each with a pumping capacity of 1.1 m3/s (40 cfs), are located behind vertical traveling screens near the terminus of the separation chamber. Traveling screens are equipped with screen washers to prevent fish and debris from being entrained in the pumpback system. During periods when one or no pumps are operating, water is discharged through a secondary fish-return pipe.

The screening facility is oriented in the canal at a 26-degree angle to the canal flow. This orientation provides a differential between the approach velocity and the sweeping velocity at the screen. Approach velocity is that component of the water velocity perpendicular to the face of the screen. Sweep velocity is that component of the water velocity parallel to the screen face. During normal operation, the approach velocity is less than 0.014 m3/sec and the sweep velocity is greater than 0.057 m3/sec. This velocity differential was incorporated into the screen design so fish will not be impinged on the screens, but will be safely guided into the flow control structure and back into the Yakima River.

Figure 2. Flow Control Structure and Fish Bypass System in the Sunnyside Canal Fish Screening Facility