Measurement of flow.

There are plenty of reasons for wanting to measure flow in open channels. In water treatment works dosing of a stream of water with some reagent is a normal process that may not need to be carried out very accurately but needs to be carried out by methods better than guesswork. The management of a river and all the inflows to it require some record keeping if, for instance, a decision is required on the advisability of extracting water for drinking or process use. The flows from springs vary in unexpected ways and records of the flows over very long periods may be extremely useful. Here we will examine two devices for measuring flow, the broad-crested weir and the venturi flume.