Air blower altimeter model BLVM-100
The basis of the function of this system, which is to accurately measure the height of water in dam reservoirs, is to inject compressed air to the lowest point of measurement by a blower pipe and to measure the injection air pressure.
The measured pressure will be equal to the point water pressure and will be proportional to the height of the water. Measured wells online.
Another model is the LVLM-100 altimeter.