Aquaculture Engineering

Water control structures or Gates - Pond inlet gates

Unit 11 - Water distribution and control structures

Water control structures or Gates

Pond inlet gates
Pond inlet gates regulate the flow of water from feeder channel into the various ponds. The two most commonly used pond gates are P.V.C. pipe made and open type. They are usually designed for allowing free fall of water from feeder canal into the ponds. A typical design of P.V.C. pipe made pond inlet gate is shown in Fig. It consists of P.V.C. elbow or bend and two pieces of P.V.C. pipes. The top edge of the elbow or bend is usually flushed with the bed of the feeder channel and at the bottom; a P.V.C. pipe is horizontally fixed into it. The vertical P.V.C. pipe piece fits into the top edge of the elbow or bend fitting and is detachable. The length of this vertical stand pipe should be higher than the maximum designed depth of water above the particular inlet gate in the feeder channel. The flow of water into the pond is accomplished by taking out the vertical pipe and is checked by pressing it to its original position. The outer diameter of both P.V.C. pipe pieces and the inner diameter of the bend or elbow should be same. The discharge capacity of this type of pond inlet gate can be computed by using the equation.

D = Internal diameter of the pipe (m)
g= Acceleration due to gravity 9.81 m/sec²
H = The vertical height of the water at its free surface in the feeder canal above the central axis of the horizontal pipe (m)
C_d = Co-efficient of discharge, value of which may be taken equal to 0.81 for length of pipe equal to 3 times the diameter i.e., for L = 3 D
C_d= 0.71 for L = 25 D, C_d= 0.64 for L = 50 D