Wednesday, July 19, 2023

Canal automation for efficient use of water in agriculture

 

Pradeep Purandare


Making our irrigation systems compatible with the demands of the 21st century is the real challenge before us.  While technology is not everything, refusal to learn lessons from experience is also resulting in continued inefficiencies in canal automation. Irrigation projects need to change with times and all that is needed is a systemic approach.


Discussions on efficient use of water in agriculture many a times take an elitist turn. Farmers are generally blamed for the in-efficient use. The systemic issues are either down played or completely ignored. It is taken for granted that “all is well” regarding physical system that conveys water from source to farm.

Maharashtra is one of the progressive, industrialized and urbanized states of India. A close examination of the nature of irrigation projects, their potential, utilisation and the irrigation efficiencies bring out the need for modernising irrigation systems.

Case of Maharashtra

Though surface water allowed to use by the interstate water tribunal is 1,16,467 MCM, as much as 55% of that volume of water is available in Konkan area where there are constraints in making use of the same. Maharashtra, therefore, could, so far, create only 38% design live storage. Though most of the irrigation projects in Maharashtra have been designed only for irrigation, water use for irrigation in 2020-21 was 58.6%.  The remaining 41.4 % water was used for non-irrigation purpose, which includes domestic, industrial and others. The ‘others’ category which remains undefined and strangely 15% of water use is categorised under this ‘others’ category. Around 15.6% water gets lost in the rivers and 16.7% of the water gets evaporated.

Irrigation – Potential and Utilisation

Maharashtra has so far completed 3877 state sector irrigation projects, which includes 87 Large, 297 Medium and 3493 Minor projects. The State has created 73.494 lakh ha irrigation potential as against the Ultimate Irrigation Potential of 85 lakh ha. The actual irrigated area of state sector projects was 41.6 L ha (77%). Information of local sector projects is not available. These projects unfortunately fall in the “built & forgotten” category – absence of management being the main reason.

The average actual Irrigated Area of state sector projects is only 45.4% of created Irrigation Potential if well-irrigation is not considered. With well irrigation it increases to 69%. Theoretically speaking, well irrigation is an accident. It is not provided for in the planning. The capital as well as recurring expenditure on  well irrigation is done by farmers themselves. On an average the area under sugarcane (483000 ha) in the command is 60% of the average area under sugarcane in the whole State.

Dams do not get filled up to their full capacity; the average actual live storage being 64%. This happens due to two reasons. First, in order to make project feasible, inflated availability of water is considered. Second, there is authorised /unauthorised upstream abstraction of water due to additional medium & minor irrigation projects and farm ponds in the catchment of the project. Water impounded anywhere by any means for any purpose have an equivalent downstream effect; water management being a zero-sum game.

Overall Project Efficiency

It is required to understand that Overall Project Efficiency (OPE) is a product of efficiencies of all components. It is determined as given below

OPE = Emc * Edyy* Eminor* Efc* Efarm (where, Emc means efficiency of main canal, Edy means efficiency of distributary; Eminor means efficiency of minor; Efc means Efficiency of field channel and Efarm means Field Application Efficiency). Every component is important. Any component with low efficiency brings down the OPE.

Component

 

Efficiency

Lined canal

Unlined canal

Main canal

0.95

0.85

Distributory

0.9

0.85

Minor

0.9

0.85

Field Channel

0.9

0.85

Field application

0.75

0.75

OPE

0.52

0.39

Main Canal, Distributary and Minor together form the main system (Fig-1). It is generally under govt control. Responsibility of field channel and on-farm irrigation is with farmers. But, where Water Users Association (WUA) is formed, the minor is also handed over to WUA.

As per MMISF rules, 2006, WRD, GOM has prescribed the following component wise efficiencies. The Overall Operating Efficiency for lined and unlined canals is 52% & 39% respectively. That simply means if 100 units of water is released at canal head, only 52% water would be delivered at root zone in case of lined canals. In the case of unlined canals, a similar figure would be 39%..

It should be noted that the component wise efficiencies considered above are `design’ values! Actual values may be even 50% of the design values depending upon the physical status of canals. The point to be seriously noted is: The present type of canals are highly inefficient with 75 to 80 percent water being lost in conveyance.  The design efficiency of govt controlled lined & unlined Main System (i.e. Main Canal, Distributory & Minor) works out to 77% & 61% respectively.

Since this Main System is not adequately maintained and properly managed, WUAs / farmers don’t get promised quota of water in planned number of rotations, at right time, at proper place for declared duration. Hence, the anarchy in the command of irrigation projects!  This mismanagement adversely affects irrigation on farm and performance of WUAs too. Conventional inefficient Main System and pressurised irrigation on farm is a weird combination which seldom works without the support of well-irrigation.

In view of above, it is high time the state should seriously think about modernization of its irrigation projects.

Fig-1: Main System

Current Characteristics and Constraints – how to overcome them

Large scale public sector irrigation projects in Maharashtra provide water not only for irrigation but even for non-irrigation [drinking, domestic, industrial, etc] purposes. They are expected (but not designed for) to simultaneously achieve multiple and at times, even competitive / conflicting objectives. Existing irrigation projects in Maharashtra are upstream controlled, manually operated, mostly open channel systems without any arrangement for operation of Head Regulators & Cross Regulators based on Real Time data. Their present performance is obviously an outcome of their original nature and inherent characteristics. It would not be correct to expect something for which the system is not designed.

Measuring devices on Canals and DISNET in almost all projects are not provided/constructed. If at all there are measuring devices, it is quite likely that they may be suffering from common problems, namely, wrong design, improper location, defective construction, poor Maintenance and Repair (M&R) and unreliable records. The situation regarding Water Meters on pipelines of non-irrigation schemes is not very different. There appears to be no systemic and systematic plans for provision, installation, maintenance, repairs and calibration of water meters in adequate numbers

Cross bund to get ‘proper level’

Irrigation projects in Maharashtra are basically Upstream Controlled Systems. Such systems work as per the logic of supply side management. Water level upstream of control element (e.g. Cross Regulator) is maintained. Changes in discharge are initiated at the upstream end by the system operators who obviously take decisions of their own convenience. Needs and demands of water users are seldom considered. Decisions taken by the bureaucracy are thrust upon the users. Majority of users, therefore, usually get inadequate volume of water mostly at wrong time for unpredictable duration. This is the main reason behind the dismal performance of Water Users Associations. Though Participatory Irrigation Management (PIM) has been accepted in Water Policy and provided for in the Acts & Rules, the conventional Main System is just not compatible for PIM simply because it has not been designed, from engineering point of view, for such a paradigm shift.

Downstream controlled systems, on the contrary, work as per the logic of demand side management. They are designed for Participatory Irrigation Management. Water level downstream of control element is maintained. Changes in discharge, in an already filled canal, are initiated at the downstream end by the users / WUAs. They start taking water, their demand gets transmitted upstream through water itself and finally the system responds by releasing matching discharge. It is designed for “On Demand” logic from engineering point of view. For example, dynamic regulation on Majalgaon Project was one of the variants of downstream control systems! It is necessary to revisit Majalgaon Project where this concept was introduced way back in early 1990s.

HR and CR not in use

Therefore, it is proposed that a new project may be designed, on pilot basis, using principles of Downstream Control systems. Further, Mains system can be modernised through many other measures too. Unless the Main System is modernised and its characteristics are changed, there would not be any significant improvement in its performance. Main System with facilities to control, regulate, measure water level and discharge are immediately required. Better the Main System, better will be the Water Management, Governance & Regulation (WMGR) which, in turn, would help improve actual use of water by different utilities.

Some possible solutions

1.      Modernising Regulators and Gates

·         Provide motorised HR & CR gates and protect, maintain and operate them by respectively implementing Water Laws, creating Special Gates M & R Mobile Units and appointing trained system operators.

·         Replace conventional HR gates by Distributors and conventional CR gates in main canal by automatic gates and that in Distributaries by  Duckbill or Diagonal weirs.

·         Introduce Supervisory Control And Data Acquisition (SCADA) on main canals of major projects to start with.

Go for a “proper mix” of above 3 solutions together. It is proposed that pilot projects may be taken up to try above solutions.

1.      Modernisation of Measuring Devices

There could be three ways, as follows, to improve the situation.

·         Provide measuring devices on a large scale. Do flow measurement as per WALMI Publication No 36, MWRRA’s Technical Manual for Water Entitlement, MMISF Act, 2005 & Rules, 2006 and MWRRA Act, 2005.

·         Switch over to indirect measurement of water. Requirement of measuring devices can be reduced if conventional HR gates are replaced by Distributors. These structures release known & constant discharge. Volume can be obtained only by measuring the time for which that discharge is given.

Go for a “proper mix” of above 2 solutions together

Proposed Roadmap for switching over to Volumetric Supply systems

Volumetric Supply demands reasonably well maintained and operated system with conveyance losses and filling time within permissible limits. It requires functional gates of HR & CR with Q-tables to control and regulate water levels and discharge; functional, accurate and calibrated Measuring Devices (MD); trained canal operators in adequate numbers for operation and maintenance of gates, MDs and to keep reliable records of flow measurement; special Gates & MD Repairs Mobile Units  for prompt and adequate Maintenance and Repair.

Conclusion

Volumetric Supply (VS) is an accepted principle. The issue of  `Why’ & `What’ parts of the systems have already been addressed in State Water Policy and several publications. But the bigger dilemma is –  How? When? To what extent?  By whom? At what cost?. Introducing Volumetric supply systems at individual Water User Association’s level is comparatively easy. Introducing them at project level is a real challenge. What is necessary and warranted is a Systemic Approach.

New systems would also generate new opportunities which include, industrial production of HR & CR gates, duckbill weirs, measuring devices & water meters and provision, installation, maintenance, repairs, calibration, automatic data collection, etc. CTF, SRO & Distributors can be manufactured by local small / medium industrialists after some training. It’s a very big business opportunity for our entrepreneurs. They can also take up Annual Maintenance Contracts & calibration work; Gates Directorate / workshop have experience of developing radial gates; Agreements with international companies can also be done for transfer of technology

Modernisation is eminently possible. How to make our irrigation systems compatible with demands of 21st century is the real challenge before us.  Technology is not everything! Agreed!  But indifference and refusal to learn lessons is also not correct. Water sector and especially, the irrigation projects need to change with times. There are global examples too. National carrier in Israel, California Aqueduct in USA & Provence-de-canal in  France are some of the best examples of Main System with canal automation.

References

WRD, GOM, Water Resources Management, 11.1 Irrigation, Report of Integrated State Water Plan committee, 2017

Pradeep Purandare, Making Irrigation Systems Compatible & Amenable to Modern Concepts and Improving Institutional & Legal Arrangements, A submission to the drafting Committee for National Water Policy on 27.1.2020

Pradeep Purandare

Retired Associate Professor, WALMI, Aurangabad.

Expert and Member, State Level Committees and Expert Panels

Blog: jaagalyaa-thewhistleblower.blogspot.in, M 9822565232, E-mail: pradeeppurandare@gmail.com

 

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