HEADWORKS
Hydraulic Structure are of two types:
1. Storage Headwork
2. Diversion Headwork
STORAGE HEADWORK
DAM
Storage headwork involves the construction of dam to store the excess water during monsoon and to supply the same during dry period.
Dam is an obstruction built across a stream or a river. At the bank of this barrier, water is collected.
PURPOSE OF DAM
Irrigation, Water supply, Hydro power generation, recreation, flood control
FACTORS GOVERNING THE SELECTION OF DAM SITE
a) Foundation
b) Economy
c) Topography
d) Spillway
e) Material
f) Water tight reservoir basin
g) The value of land property
h) Easy accessibility
i) Healthy living environment
TYPES OF DAMS
Based on use:
i) Storage Dam
ii) Diversion Dam
iii) Detention Dam
Based on Hydraulic Design
i) Overflow Dam
ii) Non-overflow Dam
Based on Material used
A) Rigid dam
i) Gravity Dam
ii) Arch Dam
iii) Buttress Dam
iv) Steel Dam
v) Timber Dam
B) Non-Rigid Dam
i) Earth Dam
ii) Rock-fill Dam
DIVERSION HEADWORK
It diverts the river water into the canal:
a) It diverts the river water into the canal
b) Regulates the intake of water into canal
c) Controls the silt entry into the canal
d) Reduces fluctuations in the level of supply in the river
e) Stores water for balancing the demand supply over small periods.
PARTS OF DIVERSION HEADWORK
1. Weir / Barrage
2. Divide wall
3. Fish ladder
4. Log channel
5. Pocket or approach channel
6. Scouring sluices
7. Silt prevention devices
8. Canal head regulator
9. River training works
10. Piers and abutments
11. Protection works
WEIR
Solid obstruction put across to raise it's water level and divert the water into the canal.
TYPES:
1. Vertical drop weir
2. Sloping weir
a) Masonry or concrete slope weir
b) Dry stone slope weir
3. Parabolic weir
SILT PREVENTION DEVICES
Minimum velocity 2-3 m/sec
1. Silt excluder
2. King's vanes
CANAL HEAD REGULATOR
i) 90 to 127 degrees to the axis of weir
ii) For minimum sediment entry into the canal, 109 to 110 degrees
iii) Crest of regulator 1m higher than under sluice crest.
RIVER TRAINING WORK
i) Protect river from changing it's course and to avoid out flanking (leaving) of structures like bridges, weirs, aqueduct.
ii) To prevent flooding of surrounding area
iii) To prevent the river banks
iv) To prevent minimum water depth
TYPES OF RIVER TRAINING WORK
i) Marginal embankment / levees
ii) Guide banks
iii) Groynes or spurs
iv) Artificial cut-off
v) Pitching of river banks
vi) Pitched Islands
*****
Other Links:
