The safety and performance of many existing irrigation systems could be improved by doing the preventive maintenance activities. Modeling, canal irrigation systems in terms of condition and performance that can be directly correlated with particular canal system maintenance activities. There are two categories of scheduled maintenance activity in irrigation maintenance systems: maintenance may be targeted towards restoring deliveries ("Restorative maintenance"), or towards reducing the risk of failures ("Preventative maintenance"). This paper covers the latter kind of maintenance scheduling by 'Risk Analysis. The purpose of this risk analysis is to forecast the impact of preventative maintenance on deliveries from the main channel systems. After gaining the experience from the preliminary risk analysis through questionnaire based survey and failure history of past record, a 'Fuzzy Fault Tree (FFT)' method is developed for the rapid risk assessment and it is necessitated for the irrigation system manager/engineer. 'Risk Analysis' of irrigation systems from the point of view of maintenance is studied and applied to the Tirunelveli Channel Systems located in India. The effectiveness is calculated for each preventative maintenance tasks and it is ranked according to the Effectiveness/Cost ratio.

Rational methods for setting priorities formaintenance of irrigation systems aredeveloped. The methods, which are aimed foruse by irrigation system managers, describethe link between maintenance activities andthe consequent improvement in theperformance of an irrigation system.Hydraulic analysis methods are developedfor assessing potential `restorativemaintenance' tasks, which are usuallyundertaken to increase the deliveries ofwater to the outlets. The new methods useinputs that have been limited to thoseeasily available from scheme records, theknowledge of irrigation agency staff andfrom infrastructure inspections. Twoalternative methods are developed, onebased on Fuzzy Logic and one on numericalmodelling. Risk analysis methods are alsodeveloped for assessing `preventativemaintenance', to reduce the probability ofsupply failures. Benefit-cost ratios arederived that allow direct comparisonbetween maintenance tasks of each type. Themethods are tested at two irrigationsystems in Tamil Nadu, India.