Suspended load and bed load in irrigation furrows

The circulation of water in irrigation furrows is a well-understood physical process. However, theoretical understanding of sediment dynamics is less well established. This study assesses an approach to determine the sediment load in irrigation furrows, involving the use of a suction device for sampling water with suspended sediments at various depths, and a trap for sampling water with sediments moving next to the furrow bed. In addition, an acoustic velocimeter is used to acquire flow velocity profiles, which allow sediment loads to be calculated when combined with the sediment concentration measurements. Use of these devices in irrigation furrows showed that the total sediment load decreases with successive irrigations, and increases as it moves downstream, while the bed load decreases. The bed load represents a small fraction of the total load. nt load can be determined with sufficient accuracy for research purposes using simultaneous measurements of the signal-to-noise-ratio of an acoustic velocimeter and the flow velocity. Estimation of the load from point measurements at half the flow depth slightly underestimates the integrated load.