Recently, it has been understood that improvement of tertiaries and on-farm water management are most important for large scale paddy irrigation projects. The Miyata Yosui Land Improvement District (the Miyata LID) in Aichi Prefecture, located in central Japan is used as a case study in this paper. During the 1970s, rapid urbanization in and around the command area caused a ntimbei, of problems in the operation and maintenance of the irrigation system, including difficulty in recruiting OM workers, water contamination by trash and effltient fron)the expanding city area, decreasing income and increasing costs in running the LID.
The Miyata LID and some other LIDs decided to rehabilitate their main facilities (including replacement of open ditches with pipelines) and install telemetric control and monitoring units with a centralizing control system. This system is not an optimizing water distribution system which automatically determined by computer when to irrigate and how much water sho
uld be, applied linking soil water depression and meteorological data. Only major structures are controlled and monitored from the remote central site.
The niodern system has made it easy to operate and maintain the canal system, and is labor conserving. The Miyata LID has been satisfied with its use of the pipeline system to prevent water contamination, however, some unexpected problems have arisen. Small gates/valves and many direct inlets which were not equipped with TC/TM units caused imbalances of water distribution in the system. The pipeline system brought about the loss of the reuse system of agricultural return flow. The available water source of return flow has been lost. These problems neccesitate additional OM workers. Also, as irrigation scheduling has not been altered, LID operators and farmers have still not reaped full benefit from the system. For the success of modernization, more attention should be directed towards institutional matters (soft ware) related to the new system (hard ware).