Canal Regulation Work - Short Questions and Answers

Canal Regulation Work - Short Questions and Answers Points : canal regulation work - short questions and answers Q.1: Define the regulation work of canals. Ans: Any structure constructed to regulate the discharge, full supply level or velocity in a canal is known as a regulation work. Q.2: Write down the name of various regulation works. Ans: The various regulation works may be categorized as under:
1. Canal fall
2. Head regulator or head sluice.
3. Cross regulator.
4. Canal escape.
5. Canal outlet Q3: Write down the difference between head regulator and cross regulator. Ans: Head regulator and cross-regulator regulate the supplies of the off-taking channel and the parent channel respectively. Q.4: Write down the merits and demerits of falls. Ans: Meter falls are those which also measure the discharge of the canal. The non meter do not measure the discharge For a fall to act as a meter, it must have broad weir type crest so that the discharge co-efficient is constant under variable head. Q.5: Write down the necessity and location of fall. Ans: Fall is an irrigation structure constructed across a canal to lower down its water level and destroy the surplus energy liberated from the falling water which may otherwise scour the bed and banks of the canal.

We have seen in chapter 14 that the canal requires a certain slope, depending upon the discharge, to overcome the frictional losses. This slope may vary from 1 in 4000 for a discharge of about 1.5 cumecs to about 1 in 8000 for a discharge of 3000 cumecs. This slope is, therefore, quite flat in comparison to the available ground slope of an average value of 5 to 20 cm per kilometre length.

1. (1 in 200 to 1 in 50). Thus the ground slope in nature is always very much steeper than the design bed slope of irrigation canal, based on the silt theories.

If an irrigation canal, taking off from its head, is in cutting, it will soon meet with condition when it will be entirely in embankment.

2. It has been stated earlier in chapter 15 that if the canal is in embankment, the cost of construction and maintenance is very high and at the same time the percolation and seepage losses are excessive. Also, there is always a danger of the adjacent area being flooded if come cut or breach takes place in the canal banks. Hence, the canal should never be in high embankment: However, the divergence between the gentle bed slope of canal and the steep ground slope throws the canal in embankment after certain distance though it started in cutting at its head. To overcome this difficulty,, falls are introduced at appropriate places, and the water surface of the canal is lowered. Arrangements are made to dissipate the excess energy liberated from the falling water to ½ to ¼.

3. The Location of a fall is decided from the following considerations

4. For the canal which does not irrigate the area directly, the fall should be located from the considerations of economy in cost of excavation of the channel with regard to balancing depth and the Cost of the falls itself.

5. For a canal irrigating the area directly a fall may be provided at a location where the F.S.L. outstrips the ground level, but before the bed of the canal comes into filling. After the drop, the F.S.L of the canal may be below the ground level for two kilometer.

6. The location of the fall may also be decided from the consideration of the possibility of combining it with a regulator or a bridge or any other masonry works.

7. A relative economy of providing large number of small falls v/s small number of big falls should be worked out. The provision of small number of big falls results in unbalanced earth-work, but there is always some saving in the cost of the fall structure.