By John Mueller, Abiquiu Lake project managerMarch 14, 2019
ABIQUIU LAKE, N.M. -- Throughout the 56 years the U.S. Army Corps of Engineers, Albuquerque District has been operating Abiquiu Lake as a flood control and water supply dam in the Chama River Valley of northern New Mexico, daily lake elevation readings have historically been taken from an internal structure known as the float well. A float well is a common feature of many dams and is typically a 36-inch diameter, vertical pipe located in the control tower filled with reservoir water to the current lake level. A calibrated measuring tape is run to a float resting on the water's surface that allows the lake level to be determined and ultimately the amount of water storage that is relayed to the Albuquerque District's Reservoir Control Branch for accounting purposes.
Although this method of capturing lake elevation has been used for many years, concerns have recently arisen that require a fundamental change to the use of the float well system. These concerns are tied to the design, and include the inability to properly flush the system resulting in inaccurate elevation readings. Additionally, as the components age, there is an increased potential for failure resulting in reservoir water flooding the entire control tower, causing catastrophic damage to the electrical and hydraulic gate equipment.
In order to address these concerns, Albuquerque District staff at the lake and in the Reservoir Control Branch teamed up with the Rio Arriba field office of the U.S. Geological Survey New Mexico Water Science Center to install a new method of measuring the lake elevation. This would allow the float well to be decommissioned.
The new device is called a bubbler system. Bubbler systems measure water levels based on the amount of pressure it takes to push an air bubble out of an orifice line and into the reservoir. The orifice line is a long metal half-inch pipe that runs from the bubbler shed down into the reservoir. The pressure required to move the air bubble changes with the elevation of the water. As the water's elevation rises and falls, so does the line pressure needed to discharge bubbles. The line pressure value is measured in PSI which refers to pounds of force per square inch. The PSI is then converted into elevation feet to represent the water level from the point of discharge to the water's surface.
The new bubbler system was installed in December 2018 and is currently in use and will soon have the capability to transmit readings remotely. The Abiquiu float well is scheduled for decommissioning in summer of 2019.