Geoscience Reference
In-Depth Information
Sediment Investigation at the 30
Water Intake
Mehdi Karami-Moghaddam, Mahmood Shafai-Bejestan,
and Hossein Sedghi
1
Introduction
The study of flow division in open channels, which has been under consideration by
hydraulic engineers for many years, is much used in designing the irrigation and
drainage networks. Water intakes are used to divert flow from a main channel into
irrigation systems and from a river into irrigation channels, at installation of water
treatment and entrance for hydropower. The configurations of diversion flows are
either natural, as braiding that causes a cutoff in meander rivers, or artificial
diversion flows, as intakes from rivers for agricultural, industrial, and urban usages.
One problem occurring in most intakes is the change of direction of the thalweg
path toward the opposite bank which arises from gathering and influence of sedi-
ments into the entrance. The sediments delivery, if not restrained, may transmit into
the channels and installations, thereupon carrying and depositing them in different
parts. Small ting particles suspended in water render damage to the installations in
case of high flow speed, especially when mechanical tools such as turbines and
pumps are applied. Among the afore-said problems are the following: (1) Reduction
of the flow discharge capacity in the channels as a consequence of sedimentation.
(2) Rough materials could lead to erosion of the channel walls. (3) Interruption of
water source for dredging of the channels may cut the water supplies providing to
the farms. (4) Channel dredging is expensive and not economical. (5) Sedimenta-
tion facilitates the conditions for growing weeds that are harmful to the covers and
result in leakage from the channel walls.
Figure
1
shows the great intake of Ohio River, in which the gathering of sedi-
ments in the entrance causes a decrease in the flow width, and so in the efficiency
(Neary et al.
1999
).
