Gated or ungated : water control in government-built irrigation systems : comparative research in Nepal

T.M.S. Pradhan

    Research output: Thesisinternal PhD, WU


    The control, allocation and distribution, of water is the core process of an irrigation system. It is the process by which the available water is divided and distributed to the smaller irrigation units within the system, which in turn is distributed further down to the individual water user who must control it to place it in the crop root zones in particular fields. This study is based on the thesis that water control is a function of both technical/engineering, and organizational and institutional arrangements (social) controls. The combination of the physical system and organizational arrangements in an irrigation system determines how much water goes where. An analysis of both aspects in the context of the local farming system should lead to the better understanding of the more general issues and complexities of water control in irrigation systems.

    This study presents three cases studies on water control in government-built and managed irrigation systems in the tarai Nepal. Water allocation and distribution practices during the consecutive crop seasons in the three irrigation systems located in three different places in the tarai region were studied from October 1991 to May 1993. There were two principal reasons for focusing research on the tarai irrigation systems. The first is that this region has the greatest number of and the largest area covered by government-built and managed large to medium scale irrigation systems. The second is the challenges and complexities in water control in the government-built and managed irrigation systems. An integrated approach which combined the study of the technical design and of organizational arrangements was followed. The historical development of the irrigation systems has also been traced to see the change or evolution of technical pattern and management practices over time. In addition to the study of the technical design of the irrigation systems, the concept of practice, which in this study refers to the visible actions and undertakings of people, has been used to understand how a certain type of water control technology provokes particular activities of water allocation and distribution. Both quantitative and qualitative data have been used.

    There is historical evidence that canal irrigation in Nepal has been practised by farmers for centuries, but the development of modern canal irrigation systems in the country began only in the 1920s. The Department of Irrigation, established in 1951, is responsible for the planning, development and management of government irrigation schemes in the country. It consists mostly of civil engineers and is largely construction-oriented.

    Government investment in irrigation development - especially in the large irrigation systems in the tarai - has increased tremendously since 1970, with the increase in the borrowing of international capital in the form of loans and grants. The development of irrigation facilities has been focused in this region because it has the largest area of irrigable land and the greatest potential for agricultural output using the river water resources. Until the mid-1980s, irrigation development by the government was largely confined to the construction of physical infrastructures of canals and structures, and very little attention was given to the effective management of the completed systems. From 1985, attention began to be paid to the improved management of government-operated irrigation systems. This move was also influenced by the external donor agencies involved in the irrigation development. Further, the Irrigation Regulations promulgated in 1989 emphasized the participation of farmers in all phases of irrigation projects, the operation and maintenance of the government-built and controlled irrigation systems in particular. The premise of increasing farmer participation was that government resources alone were inadequate to meet the country's irrigation development objectives and sustain the management of government irrigation systems after their completion. The same year, action plans for the turnover of small irrigation systems and the participatory management of large irrigation systems were formulated. Subsequently, in 1992, the government adopted a policy under which the management responsibility of the government-built and operated irrigation systems are to be gradually transferred to farmers who are organized into water users' organizations. Under this policy, the irrigation systems serving command areas over 2,000 hectares (in the tarai ) are to be jointly managed by the government and the water users' organization, and the management of the irrigation systems commanding less than this area are to be totally turned over to the water users' organizations.

    Two modes of irrigation system development can be distinguished in Nepal: extensive and intensive development. In extensive development only basic minimum infrastructure, such as main and distribution canals, are provided and irrigation blocks are typically large, from 250-500 hectares. In intensive irrigation development, physical facilities are extended further down to the tertiary or farm level. The size of an irrigation block is reduced to 30-50 hectares. In recent years, emphasis has been placed on intensive development with farmer participation, to achieve the irrigation potential as envisaged in the design. In Nepal, these two development modes have been influenced by the resources available.

    Irrigated agriculture in the tarai is basically rice based. Paddy, the staple crop, is cultivated during the monsoon season, followed by the cultivation of mainly oilseeds and wheat in the winter season. Whereas paddy covers almost all the land area, the coverage by winter crops is less intense. However, the cropping intensity varies from one place to another within the region. Farming is labour intensive and traditional methods are generally employed. Landholdings are fragmented and farmers practise intensive fanning on smallholdings. Where irrigation water is available throughout the year, the most intensive fanning is the cultivation of two crops of paddy followed by a winter crop of wheat.

    The irrigation systems in the tarai region are run-of-the-river systems and have been built primarily to irrigate rice in the monsoon season. They are therefore subjected to inter and intra-seasonal variations in the water supply. Their operation is upstream-controlled and supply oriented. The canals in most irrigation systems are unlined.

    However, the three irrigation systems studied show that the government-built and managed and controlled large canal irrigation systems in the tarai have varied technical design and operational features for water control. The difference in the water control technology is mainly because of the different design approaches followed by the design engineers, especially foreign consultant engineers. The involvement of different groups of design engineers is largely because of the government's position in irrigation development in the country vis-à-vis different external financing or donor agencies, such as ADB, World Bank, USAID and so forth. The government has to commit to involve foreign design engineers at the time of loan or grant agreements. The consultants are placed in an authoritative position. This situation is favoured by the fact that the Planning and Design Division of the Irrigation Department is not strong enough to discuss, check and question the compatibility and appropriateness of the designs of the consultants. The consequence of the involvement of foreign consultants on the choice of technology could not be foreseen.

    The first case study, the Banganga Irrigation System, comprises a fully regulated water control technology with manually adjustable gates down to the tertiary outlets. The design engineers emphasized the efficient use of the available water vis-à-vis flexibility in the system operation, given the water constraint. Whereas this fully regulated technology potentially enables an irrigation system to deliver and distribute differential water requirements to the canals and outlets under the conditions of fluctuations in water availability, it considerably increases the operation and maintenance burden of the agency operating the system. It requires frequent resetting of gates at each variation of flow and is therefore complicated and the control structures become the targets of vandalism.

    The second irrigation system, the Pithuwa Irrigation System, which was designed initially by the engineers of the Irrigation Department and later remodelled by the farmers, is a nonflexible system. It does not have adjustable control structures except for the head regulator of the main canal. The available flow in the main canal is distributed to all branch canals through open pipe outlets whose sizes are proportional to land area served. In this technology, the management input in terms of the operating staff is reduced to the minimum: the operation of the main canal headgate. Interference by people (including farmers) in the distribution of water along the main canal is reduced.

    In the third case study, the Mahakali Irrigation Project (Stage I), the water control technology is based on the "structured" design concept. In the "structured" system design, regulation of flow is only required above the structured level. The level of structuring can be fixed at any point above the chak outlet up to the headgate at the diversion point. The "structured" system design thus makes the management of the irrigation system relatively easier, as compared to the fully gated controlled technology as in Banganga. But it reduces the flexibility in water distribution in the irrigation system. The Mahakali Irrigation System (Stage I) is "structured" such that flow regulation in the main canal is only required to operate secondary canals at full supply flow, and the flow in secondary canals is divided through the fixed weirs with proportional openings and all the tertiary outlets are set for a fixed discharge.

    Compared in terms of the "structured" system concept, the three irrigation systems differ in their level of structuring. Whereas Banganga has the lowest level of structuring, at the tertiary outlet, Pithuwa has the highest, at the headgate of the main canal. Accordingly, they present different operational flexibility.

    Many engineers have a bias towards "modern" technology and operational flexibility in irrigation systems. From the case studies presented in this thesis, it is concluded that the extensively gated technology for operational flexibility needs to be reconsidered, if effective water control is to be achieved. The semi-flexible technology based on the "structured" concept, as in Mahakali, might be appropriate for government controlled and managed large irrigation systems, given the operating staff and budget limitations of the Irrigation Department. The simple water control technology as that in Pithuwa appears to be appropriate for complete turnover of the irrigation system to the farmers. This water control technology needs to be reconsidered and utilized if the investments in the future irrigation development in Nepal are to realize their potential.

    Water users' organizations are created for farmers' participation in the operation and maintenance of the systems. The reliability and adequate delivery of water to farmers greatly influence on the continuity or stability of the water users' organizations. The legal recognition and institutionalization of water users' organizations enhance the continuity of the organizations, but they do not necessarily motivate farmers' participation in government controlled irrigation systems. This study suggests that the fully gated water control technology does not guarantee reliable and adequate water delivery because of the complexity in operation, especially in government-operated irrigation systems having the limitation of an inadequate skilled manpower resource. The non- flexible technology of fixed weir check structures and open pipe outlets, as in Pithuwa, allows the available water to be distributed fairly and proportionally down the system. However, the limitation of this technology is that it is not possible to alter the distribution ratios of flow, and it inhibits the effective use of rainfall, especially where rotational water distribution is applied. By comparison, the semiflexible water control technology, as in Mahakali, allows water supply to part of the system to be cut off if necessary, because of rainfall. However, this technology should be looked upon as undesirable where there is large spatial variation in soils and crops.

    Farmers' participation enhances effective water control in government-operated irrigation systems. Farmers will have little incentive to participate in collective efforts in the operation and maintenance activities if they have no confidence in the capability of the technology to deliver reliable and adequate water. The empirical evidence from Pithuwa show that simple inflexible proportional division technology complemented with strong organization for social control is effective in ensuring reliable and fair water distribution.

    Water control is a complex process requiring intensive organizational effort. Social control strongly influences the water allocation and distribution in irrigation systems. It minimizes water related conflicts and vandalism of physical control structures and enhances fair water distribution. As the case study of Pithuwa shows, social control is more effectively developed by fanners themselves than imposed by an external agency like the Irrigation Department.

    Finally this study has shown how operational realities can be different from the design engineers' assumption. Water allocation and distribution differ from that intended in the design because of management decisions and the capability of the operating agency to execute the decisions. The availability and value of water also has strong influence upon this. In Mahakali the attempt to introduce rotational water distribution for efficient water management has had little impact because the water supply is abundant.

    Original languageEnglish
    QualificationDoctor of Philosophy
    Awarding Institution
    • Horst, L., Promotor, External person
    • Pradhan, P., Promotor, External person
    Award date5 Jun 1996
    Place of PublicationWageningen
    Print ISBNs9789054855262
    Publication statusPublished - 1996


    • irrigation water
    • transport
    • water distribution
    • water policy
    • waterways
    • water management
    • irrigation scheduling
    • nepal


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