January 8, 2019 MODERNIZATION OF FLOW MEASUREMENTS ON THE COLUMBIA BASIN PROJECT CANALS
By: Joe (Gil) Stuart, Bureau of Reclamation, Ephrata Field Office
Flow measurements are critical for calculating correct discharge on rivers, streams, and canals. The Columbia Basin Project (CBP) has traditionally measured flow by use of mechanical flow meters. Use of the Price AA meter (Figure 1) was the standard method for these types of measurements until 2015.
The Price AA meter was lowered into the canal using a cable winch attached to a cable cart that was suspended above the canal from a cable way. A sounding weight was attached to the end of the cable and was used for depth determination and meter stability. Using the cable cart was dangerous and put the hydrographer at risk of falling off the cart and into the canal (Figure 2). Fortunately, flow methods have evolved since the introduction of the Price AA meter.
Today, flow at CBP sites is measured using instruments such as the Acoustic Doppler Current Profiler (ADCP). This instrument uses the Doppler principle to measure the sound frequency shift in particles found in water bodies and convert that shift into a calculated velocity used to determine flows. ADCP’s have made measurements easier, more accurate, and provide more detailed data than the old Price AA meter.
Taking measurements using a cable cart method was replaced by a rope and pulley system (Figure 3), which was significantly safer than the cable cart method. However, this method still required an unsafe practice where the hydrographer had to tie off to a stationary object to lower the equipment into the canal for flow measurements (Figure 4). To eliminate many of the hazards of both the cable cart and rope/pulley methods, the Cable Fox ADCP Towing and Positioning System (Figure 5) was purchased. This device uses the existing cable ways to position the ADCP device over the water and raise and lower it by remote control. The Cable Fox is portable (Figure 5 and 6), can be attached to any existing cable way, eliminates the need for a manned cable cart, and allows for a safer measurement controlled by the user.
Furthermore, EFO maintenance staff helped construct new platforms at the canal edge allow for safer deployment of the Cable Fox (Figures 7 and 8). The ADCP is attached to the winching system of the Cable Fox and is then remote controlled through a user interface handheld device to move the unit across the canal using the cable way. This is accomplished by accessing rebuilt metal grate platforms that are equipped with a safety railing. The platforms have new grating and the bracing is reinforced underneath the platforms. The new railings comply with the 42” height OSHA standards and have a “safety flip gate” that enables the hydrographer to deploy the ADCP without leaving the safety of the railing-enclosed platform.
Thanks to Bluetooth and remote-control technology, the Cable Fox, and ADCP, Reclamation hydrographers can make safe measurements in canals without ever having to enter the canal prism and with less worry of an unexpected fall.