Toppenish / Satus Canal

The Toppenish/Satus Unit Diversion is located at river km 6 (river mile 3.5) on Toppenish Creek, just downstream of the confluence of Toppenish Creek and Marion Drain (Figure 1). The diversion directs water from Marion Drain and Toppenish Creek to the Satus Canal. Canal operation begins in late March or early April and continues through the irrigation season, usually to mid-October. Canal capacity is about 18 m3/sec (650 cfs).

The Toppenish/Satus Screens are located about 200 m (650 ft) downstream of the headgates of Satus Canal. The facility diverts fish entering the canal and directs them back to Toppenish Creek.

Figure 1. Flow Control Structure and Bypass System in the Toppenish/Satus Canal Fish Screening Facility

A trash rack, installed immediately upstream of the screening facility, "filters" out debris entering the canal such as large logs or tree branches that may damage the screens or interfere with flow through the facility. The rack is equipped with an automated trash removal system designed to clean the upper 2 m (6 ft) of the trash racks. This system is especially important at Toppenish/Satus because of the large quantity of aquatic macrophytes that enter the canal from Marion Drain and Toppenish Creek during the summer.

The screening facility houses eight rotary drum screens with axes parallel to the length of the structure. Each screen is about 5.5 m (18 ft) wide and3.7 m (12 ft) in diameter. The screen mesh openings are 3.18 mm (1/8 in). Water depth at the screens varies with canal flow. The average depth across the face of the screens is about 2.4 m (8 ft). The rotary drum screens are installed in the canal at a 26-degree angle to the canal flow. This orientation is designed to provide a sweeping velocity to approach velocity ratio of 2:1. The maximum allowable approach velocity is 0.15 m/sec (0.5 ft). This orientation guides fish toward the fish return pipe and back to the river.

The fish bypass slot is located at the downstream end of the screening facility. About 0.6 m3/sec (20 cfs) of water pass through the fish bypass slot and out the fish return pipe. A fish sampling screen has been installed in the fish bypass slot at the Toppenish/Satus Screens, although it cannot be used because it does not include any means for cleaning.