Irrigation system design for management in mountainous areas

Abstract

The paper reports research on engineering designs of irrigation systems in mountainous areas and the resulting implications for management. The engineering designs are important because they may or may not provide the social basis for local people to participate in system development and management. This hypothesis is analyzed by using field data from an irrigation development program in the Himachal Pradesh State in India. The development program will construct about 150 small-scale, gravity flow and lift irrigation schemes in a seven year period. The results of the analysis support the argument that the engineering designs critically influence local people's capability and willingness to manage irrigation facilities. In gravity flow irrigation schemes, water capture by permanent flow diversion structuress is extremely expensive and yet unreliable because of large variation in stream flow and unstable mountain slopes. A more practical alternative is to utilize diversion structures of temporary nature which are made with local materials. Construction and management of such structures will encourage local participation because of high maintenance requirements. In lift irrigation schemes a conventional design is to lift all water requirements to a single highest point in the command area. This practice results in unnecessarily high energy costs and in a water distribution system which is complex to manage. A better alternative is to design the pumps so that water can be delivered at variable elevations in the scheme area. This will allow disaggregation of the total area into smaller rotational units and, therefore, management of water distribution can be potentially easier and equitable.