ISO 18481:2017 pdf download – Hydrometry — Liquid flow measurement using end depth method in channels with a free overfall. The flow in the approach channel shall be uniform and steady, with the velocity distribution approximating that in a channel of sufficient length to develop satisfactory flow in smooth, straight channels. Baffles and flow straighteners can be used to simulate satisfactory velocity distribution, but their location with respect to the measuring section shall be not less than the minimum length prescribed for the approach channel. c) The channel bottom should be horizontal. Gentle positive slopes not greater than 1 in...