submerged flows below the gate. For completely raised gates, Table 8.1 for
free flow and Table 9.1 for submerged flow conditions should be referred
to. Section 6.5 and equations (6.2)–(6.5) together with Figs 6.9 and 6.10
summarize the hydraulic conditions for flow under and over vertical lift
and Tainter gates.
(d) Regulators
The structures controlling diversion into a supply canal are called regula-
tors (Section 9.2). The design principles are the same as those used in the
design of barrages, except that the regulators are a smaller version of bar-
rages. The entry sill of a regulator must be such that it permits entry of the
maximum flow at various pondage levels. Another important considera-
tion in designing the regulator is silt exclusion from canals (Section 9.2).
Silt-excluder tunnels are often provided in the barrage bays adjacent to
the regulator, so that the heavier silt-laden bottom layers of water bypass
through the tunnels (Fig. 9.3).
(e) Dividing wall
The dividing wall is built at right angles to the axis of the weir, separating
the weir and the undersluices (Fig. 9.3). It usually extends upstream beyond
the beginning of the regulator and downstream to the launching apron
(talus). The sluice bay floor level is generally kept as low as possible to
create pool conditions (for silt settlement and its exclusion) and the divid-
ing wall separates the two floor levels of the weir. The downstream exten-
sion of the dividing wall provides a barrier between the stilling basin and
scouring bay, in order to avoid cross-currents. A properly designed dividing
wall can also induce desirable curvature to the flow for sediment exclusion
from the canal-head regulator. The dividing wall may also serve as one of
the side walls of the fish ladders (Section 9.3) and be used as a log chute.
(f ) Weir block and stilling basin
The weir block of the barrage is designed either as a gravity structure (the
entire uplift pressure due to seepage is resisted by the weight of the floor)
or as a non-gravity structure (the floor, relatively thinner, resists the uplift
by bending). It may be of different forms, e.g. a sloping weir with
upstream and downstream glacis, a vertical drop weir, an ogee weir, or a
labyrinth weir (zig-zag crest).
In some cases the barrage has a raised sill (crest) (e.g. Fig. 9.10). The
advantage of this arrangement is a reduced height of the gates; however,
the height of the sill must not exceed a value which could result in a raised
(maximum) upstream water level. A hydraulically suitable design for a low
sill is the so called ‘Jambor sill’ (Jambor 1959) which consists of a part