Asset management modelling framework for irrigation and drainage systems: Principles and case study application

Sustainability of irrigation and drainage infrastructure poses many challenges to many irrigation authorities worldwide due to a mismatch between the actual cost incurred in the provision of irrigation and drainage service and pricing of this service. This shortfall often leads to inadequate expenditure on maintenance in the absence of adequate subsidies from government or other sources.The asset management modelling framework (AMMF) presented in this paper enables the quantification of on-going ownership costs and operation costs. A life cycle cost (LCC) model for the evaluation of alternative irrigation and drainage asset management strategies is also presented. The AMMF is applied to the evaluation of asset ownership costs and LCC for alternative maintenance and interest rate scenarios in the Cu Chi irrigation system, Vietnam. The cost of three renewal strategies was evaluated: linear depreciation, full annuity and partial annuity. The cost ranges between US$ 28.00/ha and US$ 41.00/ha when interest rate varies between 9 and 3%. The average maintenance expenditure during recent years was estimated to be only US$ 1.30/ha which translates into 0.68% of the total asset replacement cost.The application of a simplified LCC model reveals that the least LCC varies with the level of maintenance and interest rate between US$ 353.5/ha for 5% maintenance expenditure and 12% interest rate to US$ 522.3/ha for 3% maintenance expenditure and 6% interest rate. The importance of exercising value judgements in applying the LCC model is also emphasised and discussed.