The ASFM measures discharge in hydroelectric power plant intakes.

When you need to measure flow at hydroelectric plants
Acoustic Scintillation Flow Meter (ASFM) is globally recognized as a solution to the hydroelectric industry’s toughest turbine flow measurement challenge – accurate and repeatable measurements in intakes of low-head power plants with no penstocks. The features of the method that make it a cost-effective solution for low-head plants apply equally to many higher-head plants as well.
The ASFM is a real-time, non-intrusive instrument that excels at performing:

Key words:  flow measurements, hydroelectric intake flow measurement, non-intrusive flow measurement, turbine efficiency, real-time flow measurement, accurate and repeatable intake flow measurement