MAINTENANCE OF IRRIGATION CANALS Maintenance of Irrigation Systems

MAINTENANCE OF IRRIGATION CANALS

Maintenance of Irrigation Systems • Process to improve the deteriorated condition of the irrigation systems to keep them in top operating condition. • Deterioration in the irrigation systems include: – – – Cracks in the lining General erosion Settlement of embankment or structure Encroachment of freeboard Scour, seepage and severe damage at animal crossings near to the villages • All structures and facilities are subject to deterioration in varying degrees with the passage of time.

Maintenance of Irrigation Systems • The importance of the maintenance for the success of any irrigation system cannot be underestimated. • Preventive maintenance not only pays dividends in the economical operation of a smooth working system but also means the uninterrupted delivery of water to the command area. • Objectives of Maintenance • To keep the system in top operating condition all times through proper maintenance • To obtain the longest life and greatest use of the facilities of the system by providing good maintenance and timely replacements. • To achieve the foregoing objectives at the lowest possible cost through a proper maintenance programme.

Maintenance Categories • The maintenance of all types of irrigation canals in Pakistan is usually divided in four categories, which are: – – Regular routine maintenance Seasonal repairs Annual repairs Emergency repairs

Regular routine maintenance • Refers to the day by day work items that must be accomplished to keep a system operating well • These are basically preventive maintenance functions that are undertaken on continuous basis to prevent the problems to become larger and more expensive • It includes: – – Filling rat holes, rain cuts and rain hole when observed Promptly removing trees that have fallen into canals Replacing missing stones or bricks in the lining Cleaning weeds and other floating trash

Seasonal Repairs • It is the light maintenance work, part of which has • • to be accomplished during canal closure Can be undertaken by permanent employees or casual labour hired for this purpose It is limited in extent because of short time available during canal closure • This work generally includes: – – Repairing and resetting of outlets Repairing damaged panels of lining Removing all obstruction from the bed and the sides Completing temporary repairs

Annual Repairs • It is a heavy work that is generally contracted out to private contractors or the machinery division of the Irrigation Department • It involves the extraordinary or extensive programme of replacing the damaged portion of lining and embankment slopes • It also includes the occasional large desilting works and a comprehensive raincut repair programme when required

Emergency Repairs • It refers to the repair of serious damages or failure which, unless prompt action is taken, may entail even more catastrophic problems concerning canals and farmlands. These damages are not always predictable with respect time of occurrence or to their scale • The catastrophic damages of irrigation systems may result from any of, or combination, of the following causes: – Floods or heavy rainfalls – Careless operation of irrigation facilities – Human actions such as stealing water by blocking canals, cutting canal banks, destroying gates etc. – Destruction of freeboard, or portion of lining of embankment by animals

Difficulties and Problems in Maintenance of Lined Canals • The magnitude of the problems encountered in the maintenance of canal systems is so vast and varied in nature that they need to be identified in different subgroups • They can be broadly classified into the following categories: – Operational difficulties of the canal system – Misuse and mismanagement of the canal waters by the farmers – Deficiencies in the hydraulic and structural design – Defective constructions – Inadequate staff and inadequate funding available for maintenance of canals

Difficulties and Problems in Maintenance • Operational difficulties – Many assumptions are made at the planning stage in the design and operation of canal system – Average duties adopted in the design of canal sections fall short of the peak demands in the fields – Actual conveyance losses widely differ from those accounted for in the design of canals • Misuse of water – It is a serious problem through malpractices by the farmers – This includes breaching of the canal banks, tempering with outlets and obstructing top structures

Difficulties and Problems in Maintenance • Design deficiencies – Most important aspect in the maintenance of a canal system is the design setups, both hydraulic and structural – No design method is perfect and no structure, due to economic constraints, is designed to serve its total life as trouble free – In the design, in most cases, the effect of sediment transport parameter is neglected – Much of the maintenance work could have been reduced, if proper method of design had been adopted

Difficulties and Problems in Maintenance • Defective construction – Another Major problem in operation and maintenance of irrigation canals – Defective construction includes improper compaction of subgrade, use of inferior quality material for construction, theft of cement and ineffective supervision during construction – It increases maintenance cost and creates problems for effective delivery of water to the downstream reaches

Difficulties and Problems in Maintenance • Inadequate staff and inadequate funding available – The level of existing staff is hardly able to operate the system properly and to attend the maintenance needs promptly – The maintenance funding available is insufficient to attend even temporary repairs, without considering the heavy repairs

Experience gained and Lessons learnt • Compaction of subgrade before lining is the key to the success of a stable lined section, as many reaches of lined canals in Pakistan have failed, due improper attention to this • In high water table reaches, concrete lining has a better overall performance than brick/tile lining and has less maintenance requirements • If embankments are not properly consolidated, this results in early failure of the canal lining • Inadequate drainage results in frequent failure of linings • The maintenance and operation of irrigation canals is becoming specialized job and for this a separate cadre of operation and maintenance staff needs to be established

Experience gained and Lessons learnt • Cattle ghat sites or buffalo wallows should be constructed near villages, in case of lined canals, to guard against damage by the farmers and the animals • A greater number of bridges/crossings should be provided to facilitate the traffic of nearby villages to minimize the damage by animals and tractors • Plantation on berms of canals should be discouraged, as this is injurious to linings

Section Indicating Bank Erosion at 20 Km from Canal Head of UCC Source: Shakir et al. , (2011): REMODELLING OF THE UPPER CHENAB CANAL: A CASE STUDY FROM PAKISTAN

Section with Inadequate Freeboard at 46. 3 Km from the Canal Head of UCC Source: Shakir et al. , (2011): REMODELLING OF THE UPPER CHENAB CANAL: A CASE STUDY FROM PAKISTAN

Irregular Cattle tress passing Source: Shakir et al. , (2011): REMODELLING OF THE UPPER CHENAB CANAL: A CASE STUDY FROM PAKISTAN

Deep Scour Pit d/s of Fall Structure at 50 Km from Canal Head of UCC Source: Shakir et al. , (2011): REMODELLING OF THE UPPER CHENAB CANAL: A CASE STUDY FROM PAKISTAN

Cattle ghat at some section of LBDC