Water control and diversion structures

• The structure includes check gate, portable check dams, diversion boxes, turn out boxes, siphon and pipe turnouts.

1. Check Gates:

• It is used to control the elevation of water surface upstream.
• Water level in the channel should be atleast about 8-12 cm above the ground surface.

2. Turn outs:

• When water is taken from a channel into a field, a turnout is used.
• My be portable or built in and equipped with gates to control the flow of water.
• It is of following types:

A. Box Turnouts :

• It is portable wooden boxes provided with a gate at the inlet and a baffle board at the outlet.
• The gate slides in sow-cut groves in the box.
• Adjusted to divert any desired flow into a field or a secondary channel.
• A cellar made of wooden pieces fixed around the box will prevent seepage around the box turnouts.

B. Slipes:

• Made of bamboo, concrete or baked clay pipes.
• Size varies from 2.5 – 10 cm.
• Should be placed low in the bank to reduce erosion at the outlet.

C. Siphon tubes:

• It convey water over the channel bank into a field or furrow without disturbing the wall of furrow.
• Size ranges from 2.5- 7.5 cm.
• The discharge from he siphon tube depends on the size of the tube and the difference in elevation between the water surface at upstream and downstream ends of the tube.
• Mathematically,

Q = 0.65 x 10^-3 a   v2gh l/s.

Where,

a = cross sectional area of siphon (cm²)

g = acceleration due to gravity ( cm/s²)

h = effective head causing flow (m).

D. Diversion boxes:

• In carrying water to different farms or to different parts of the same farms, it is necessary for the water course or the main channel to divert the stream into the proper channel.
• 2-way or 3-way or 4-way diversion made of check gates at the channel junction will permit the operation of diverting all or any pre-determined portion of the stream through any one of the diversion.