The floor of the sluice is laid with riffles made of strips of wood 2 in.
Broad; it has vertical shafts at intervals, and a sluice chamber at its egress from the lake.
The discharge of a river at a weir can be regulated as required and considerably increased in flood-time by introducing a series of openings in the centre of a solid weir, with sluice-gates or panels which slide in grooves at the sides of upright frames or masonry piers erected at convenient intervals apart, FIG.
The barrage at the head of the Nile delta, and the regulating sluices across the Nile at Assiut and Esna in Upper Egypt below Assuan, are examples of draw-door weirs, with their numerous openings closed by sluice-gates sliding on free rollers, which control the discharge of water from the river for irrigation.
Each pair of wheels is built in three storeys, and the outflow of the water is controlled by a cylindrical gate or sluice, which is moved up and down by the action of the governor.