CANAL REGULATIONWORKS

INTRODUCTION

• The water in the main canal coming from the river has to be divided
  into different branches and distributaries, in accordance with demand
  of water.
• The process of controlled distribution of water is called ‘regulation’
  and the works which are constructed in order to control and regulate
  discharges, depths, velocities in canals are known as ‘canal regulation
  works.
  The important type of canal regulation works are as follows:
  a) Canal falls
  b) Canal head and cross regulators
  c) Canal escape
  d) Metering flumes
  e) Canal outlets and modules

A. CANAL FALLS

Canal fall is a solid masonry structure which is constructed on the
canal if the natural ground slope is steeper than the designed channel
bed slope.

• If the difference in slope is smaller, a single fall can be constructed.
• If it is higher then falls are constructed at regular suitable intervals.
• The location of the fall depends
  upon the topography and is
  selected such that cost of
  excavation and cost of a filling is
  minimum by balancing the
  earthwork in excavation and filling.

TYPES OF CANAL FALLS

Ogee Fall:

Ogee Fall: Ogee curve is the combination of convex and concave
curves gradually.

• This gradual combination helps to provide smooth transition of flow
  and also reduce the impact.
• If the canal natural ground surface is suddenly changed to steeper
  slope, ogee fall is recommended for that canal.
• Stone pitching is provided in the upstream and downstream of the fall.

Rapid Canal Fall

• Rapid fall consists a long sloping glacis.
• It is constructed if the available natural ground surface is plane and
  long.
• For this, a bed of rubble masonry is provided and it is finished with
  cement mortar of 1:3 ratio.

Stepped Canal Falls

• As in the name itself, stepped fall consist
  vertical steps at gradual intervals.
• Stepped fall is the modification of rapid
  fall.
• It is suitable for the canal which has it
  upstream at very high level as compared to
  downstream.
• These two levels are connected by
  providing vertical steps.

Trapezoidal Notch Fall

• In case of trapezoidal notch falls, a high crested wall is built across the
  channel and trapezoidal notches are provided in that wall.
• Trapezoidal falls are very economical and suitable for low discharges.
• More energy loss.

Well Type Fall/ Cylinder Falls/ Syphon Well Drops

• Well type falls are also called as syphon drop falls.
• In this case, an inlet well with pipe at its bottom is constructed in
  upstream.
• The pipe carries the water to downstream well or reservoir.

Simple Vertical Drop-type/ Sarda-type
Fall

• Simple vertical drop fall or sarda fall
  consists, single vertical drop which allows
  the upstream water to fall with sudden
  impact on downstream.
• The downstream acts like cushion for the
  upstream water and dissipate extra energy.
• This type of fall is tried in Sarda Canal UP
  (India) and therefore, it is also called Sarda
  Fall.

Straight Glacis Fall

• This is the modern type of construction, in which a raised crest is
  constructed across the canal and a gentle straight inclined surface is
  provided from raised crest to the downstream.
• The water coming from upstream crosses the raised crest and falls on
  inclined surface with sufficient energy dissipation.

Montague Type Fall

• Montague fall is similar to straight glacis fall but in this case the glacis
  is not straight.
• It is provided in parabolic shape to introduce the vertical component of
  velocity which improves the energy dissipation to more extent.

Inglis Fall/ Baffle Fall

• In this case, straight glacis fall is extended
  as baffle platform with baffle wall.
• This is suitable for any discharge.
• The baffle wall is constructed near the toe
  of the straight glacis at required distance in
  designed height.
• The main purpose of the baffle wall is to
  create hydraulic jump from straight glacis
  to baffle platform.

NOTE

• Meter fall: If canal falls can be used to measure the discharge of the
  canal, it is called as “meter fall”.
• Non-meter fall: If it is not used to measure the discharge, then it is a
  “non-meter fall”.
• Vertical drop falls are suitable for discharge up to 15 m³/sec and drop
  of 1.5m.
• The straight glacis type fall is used for high energy loss of discharge
  up to 60 m³/sec and drops up to 1.5 m.
• Baffle wall may be used for all discharge and drop more than 1.5 m.
• Well type falls are suitable for low discharge with high drops.