長野県北信地方の果樹園における畑地灌漑の発達と水利組織

抄録

Through the examinations of the Hitakibara (the Matukawa river alluvial fan) of Suzaka City and the Yomase river basin (the Yomase river alluvial fan and the foot area of Mt. Kosha) of Nakano City, where a prefecture-operated dry field irrigation project was carried out in the 1960's, this study identified the difference between the two regions after clarifying regional characters, irrigation facilities and their utilization, and methods of maintenance and management.
(1) Both regions are occupied by orchard for a large part. However, the process of development differs. Namely, the Hitakibara was a common meadow until the middle of the 19th century and therefore there were a few of villages in the region, and was developed by farmers who crossed the village border from surrounding villages. On the other hand, in the Yomase river basin (alluvial fan), paddy fields were developed and villages were grown because of excavation of the Hachikago canal possessing exclusive water right.
(2) In both regions, water is supplied to each orchard through pipelines from pumping facilities and fixed-overhead watering systems by sprinklers are adapted. In the Hitakibara, the watering is done by operating electric valve automatically through remote control from the first pumping facility.
On the other hand, the watering in the Yomase river basin was done by hand-operated valves all over the region at the beginning. Since 1986, however, the watering in some parts of the region has been done by operating electric valves automatically through control device using solar battery in the orchard.
(3) As for the utilization of irrigation of facilities, it aims at watering for growing fruits in open orchard in the Hitakibara and the irrigation period is May 1st through September 30th.
On the other hand, the Yomase river basin is divided into watering area operated by hand and that operated automatically by electric valves. The former aims at watering for growing fruits in open orchard. Meanwhile, the latter aims at watering for growing fruits in open orchard and some parts in plastic green houses and watering to avoid frost damage and the irrigation period is April 1st through September 30th.
(4) The organization of maintenance and management of irrigation facilities is very important because of the demand for an intentional distribution of water in the dry field irrigation. In the Hitakibara, the land improvement district manages from intake facilities to terminal irrigation facilities and does watering directly, and board of maintenance and management organized by beneficiaries bears nothing but a supplementary role.
On the other hand, in the Yomase river basin the land improvement district controls intake facilities, pumping facilities and main canals, and the board of maintenance and management as village communities controls branch canals and terminal irrigation facilities in the orchard and does watering.
(5) The following have become clear by comparison of those characteristics mentioned adove.
(1) The reason why watering to avoid frost damage in the Hitakibara is not done is that the authorized irrigation period starts from May 1st and an acquisition of irrigation water at the end of April is impossible.
(2) The reason why growing of grapes (kyoho) in plastic greenhouse with heater, which can earn a lot of profits only in the upper parts of the Yomase river alluvial fan, is being done is because in this region, water for irrigation starting from February can easily obtained from the Hakkago canal.
(3) The reason why the land improvement district in the Hitakibara instead of village cornmunities manages directly from intake facilities to terminal irrigation facilities and does watering are considered as follows.
Firstly, an agricultural labor force necessary for management is becoming short due to increase in part-time farmers.