|Techno-Market Survey on Adaptation of Irrigation Canals for Navigation - Navigation in Narmada Canal|
Navigation in Narmada Canal
The Narmada Main Canal flows North from Sardar Sarovar dam with 460 Km. in Gujarat and 74 km. in Rajasthan. There are 35 branches off taking from the Main Canal, the longest being Saurashtra Branch with design discharge of 267 cumec. The Main Canal has 118 principal structures, comprising regulators, siphons, aqueducts, super passages etc. There are 8 railway bridges and 23 main road bridges crossing the alignment.
The main canal can be divided into 3 reaches based on its cross-sectional parameters. The first reach from the Head regulator to the Sabarmati Escape – 230 km long having a minimum bottom width of 58.6 m and water depth of 7.3 m. this cross-section is adequate for providing a 2 lane Normal Section for even vessels larger than Class IV (1350 T carrying capacity with Beam = 9.5 m and loaded drought of 2.8 m.).
In the Second reach from 230 km to 437 km upto last cross regulator near the Rajasthan boarder, the minimum cross-section dimension reduced to the bottom width of 10.8 and a full supply depth of 5.55 m. these dimensions are just width of 10.8 m and a full supply depth of 5.55 m. These dimensions are just about adequate for having a restricted double lane movement using a Narrow section of Class II vessels (600 T carrying with Beam = 6.6 m and loaded drought of 2.5 m).
In the last reach from the Godrisa cross regulator to the Cross-regulator at the Chitwana distributary about 22 kms before the tall end of the canal in Barmer district of Rajasthan i.e. from Km 437 to km 512 (75 km), the canal has been designed suing parameters of a mehboob section (refer chapter 3).* The minimum depth of water in this reach is 4.0 m. with this water depth the channel would have a minimum width of (4.47 x 4.0 – 2x2x1.3 =) 12.68 m which would be just adequate for single lane movement of a class I vessel (Class I vessel operated at a reduced draught of 1.3 m giving carrying capacity of 150 T i.e. 2xB =2x5.1 = 10.2 m).
The unit fleet costs of Class I vessel are lowest for the first reach of 230 km. or in case navigation takes place on both the Reach I and Reach II. For the last Reach of 75km, it would be only possible to use the modified Class I vessel operating at reduced draught with carrying capacity of 150 T.
The investments required for modifications to the Reach I, Reach II and Reach III are Rs. 1006 million, Rs. 1337 million, and Rs. 431 million respectively.
Based on these costs, the break even traffic works out to 5.4 lakh tonnes in ach direction annually, or 1554 tonnes daily in each direction.
* Mehboob section has side slopes of 1 vertical : 2 horizontal with the bottom in form of a circular arc of radius equal to full supply depth.
Conclusions, Recommendations and Plan of Action
Vast investments are already made I the field of irrigation canals, where technological status of India compares favourably with that if any other country. India has limited natural waterways which are exploitable for navigation. Successful modern navigation in man-made waterways (which present their own problems and techniques/ technologies to deal with them) is virtually absent.
Several large irrigation canal projects that have been completed in the country in the last few decades have not included inland navigation in their developmental plans. As a result, the opportunity of providing a cheap and reliable transport system at a marginal extra cost to the large areas served by these canals could have been missed out.
In certain cases it may perhaps be too late to make such modifications are required for providing navigation facilities on these canals. Yet in some others which have been constructed or are under construction/at planning stage, it may be quite viable to incorporate navigation.
The present study deals with adapting a highly developed expertise of irrigation canals to relatively less developed sector of navigation in canals in India.
1. The best time to examine navigability in an irrigation canal is at the design stage. This fact is well recognized. There have been attempts in some recent projects where navigation possibilities in irrigation projects have been examined. It was found, sometimes, that either the navigational possibility was examined solely by irrigation engineers involved in the design of the project, or the final judgment lay with them.*
It needs to be recognized that Navigation is a specialized field by itself, and in terms of expertise, as well a final users, distinct from irrigation. This is imperative for exploiting the expertise Assets being created in our resource starved economy.
* During data collection for the IG Canal system, it was to our notice that a formal advertisement was inserted in March 1989 for conducting a feasibility study for enabling navigation on the canal. However, the details/ conclusions study are not available.
While the Water Resources Policy of the Government gives a precedence to irrigation over navigation, given an irrigation project framework, navigation possibilities need to be finally decided upon by experts with comparable representation from both the disciplines.
Clear guidelines need to be prepared for effecting the above. Being an interministerial issue, Planning Commission is well placed to coordinate. Back