A procedure for planning irrigation scheme rehabilitation
The performance of an irrigation scheme is influenced by many factors - socio-economic, agronomic, environmental and technical. Factors are often interlinked so causes and effects may not be readily distinguishable. The procedure provides a checklist, a farmer questionnaire and proformas to assess the condition of infrastructure. Using these tools during the early evaluation of an irrigation scheme should help identify the underlying causes of under-performance and determine if the physical rehabilitation of infrastructure is a priority.
Background
Feasibility studies for rehabilitation projects regularly indicate high rates of return on investment, provided the assumed benefits from intervention are achieved. Unfortunately, performance audits show that returns to rehabilitation are often lower than anticipated. One reason for this is that projects tend to be formulated around improvements to infrastructure to remove perceived constraints to performance. In fact, institutional, social or economic constraints may play a greater role in reducing scheme output but these may be overlooked during the formulation of a rehabilitation project. The procedure developed under this project provides a number of practical tools that can assist in carrying out a rapid but broad diagnosis of the underlying causes of under-performance.

The Procedure
The procedure aims to identify those irrigation schemes where targeted, physical rehabilitation of infrastructure is likely to lead to improved hydraulic and agricultural performance, as measured by water supply, cropped area or crop yields. To do this, a reviews a range of possible causes of under-performance are reviewed:

  • Agricultural or economic factors
  • System design or operational factors
  • The condition of infrastructure
  • Land degradation
  • Water supply at the scheme headworks

    What it covers
    The procedure provides three main diagnostic tools:
    1. A checklist of factors potentially limiting scheme performance.
    2. A questionnaire for farmers to obtain their views on system constraints and priority needs.
    3. Condition assessment formats to determine the ‘fitness for function’ of infrastructural components.

     

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    The checklist provides the basis for structured discussion with O&M staff on a scheme and should identify the nature and approximate scale of technical and non-technical factors that influence scheme performance.

    The farmer questionnaire obtains information from the field about levels of performance, the role of infrastructure and other factors in determining that performance, and their relative importance.

    The condition assessment formats provide a standardised and consistent basis for determining the impact of condition on the hydraulic performance and structural stability of a given asset. A derived condition score can then be used as a parameter in a priority index to rank the importance of different works.

    The MARLIN software, also available from HR Wallingford as a research output, utilises basic information and procedures discussed in this document. Appendices to the document provide a number of proformas that can be used in the field in following the procedure.

    Contributors
    HR Wallingford Ltd, UK; Directorate General of Water Resources Development, Government of Indonesia.

    Intended users
    The procedure is aimed at staff in government agencies and consultants who are involved in the appraisal and identification of schemes for rehabilitation.

    Cornish, G. and Skutsch, J, 1997. A procedure for planning irrigation scheme rehabilitation. HR Wallingford, UK, Report no. OD/TN84.

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