Manual River Flow Measurements, a.k.a. spot or instantaneous flows, is a dataset of flow measurements carried out by visits to river sites. This output contains the calculated flow for each gauging, rather than the detailed measurements and calculations used to produce it. Data is held for:
• Primary sites. These are gaugings at permanent, continuous monitoring sites. Their main purpose is to check that the permanent site is calculating flows correctly.
• Secondary sites. These are gaugings at otherwise ungauged sites. They are intended as a record in themselves, where no other information is available). They may be one-off measurements or part of a planned programme.
Both primary and secondary gaugings provide a valuable spatial and temporal description of river flows across England and Wales
There are approximately 27,000 open sites. A few primary sites will have data from the 1960s to the present day.
The dataset is also known as AfA205 within the Environment Agency.
The most common techniques measure velocities across a river’s cross-section either with impellor-based current meters, or using Acoustic Doppler Current Profilers.