|Budget Amount *help
¥2,300,000 (Direct Cost : ¥2,300,000)
Fiscal Year 1998 : ¥600,000 (Direct Cost : ¥600,000)
Fiscal Year 1997 : ¥700,000 (Direct Cost : ¥700,000)
Fiscal Year 1996 : ¥1,000,000 (Direct Cost : ¥1,000,000)
The irrigation water supply control system was the most popular of all water management projects in agricultural areas till recently. But now-a-days, water management demands from rural peoples integrated irrigation, drainage and water quality, to correspond with the changing life style, the change in land use and the needs of environmental preservation. Based on this point of view, this paper presents a study of irrigation, drainage, water quality management and cultivation management in paddy fields in low-lying areas.
Because a high percentage of the Tsugaru area, Aomori Prefecture is covered by paddy fields, it has historically utilized several types of water utilization.
1. Considered are three typical examples of water utilization : the dependence rate on irrigation water from area itself, pumped irrigation water and the ratio of re-used drainage water. These factors are very important for an analysis of the quality change of irrigation-and-drainage water, the outflow load from pad
dy areas, water quality budget and re-used fertilizer.
(1) Closed circulating irrigation system area
(2) semi-open irrigation system area
(3) open irrigation system area
2. The results of the quantity-and-quality data flowing in or out of 3 types of paddy areas during the irrigation periods can be indicated as a fallows :
(1) The inflow and outflow load per unit area(ha) is small in the order of closed, semi-open. and open types irrigation system. In semi-open, and open types, the output load is large during the under-water ploughing and rice-planting periods.
(2) The water quality budget of paddy area using the closed circulating irrigation system belong to the equilibrium type, where the outflow load is approximately equal to the inflow load. But open irrigation system area belong to the pollution type.
(3) The inflow and outflow loads of Tsugaru paddy areas are smaller than those of other paddy areas in Japan. Especially, the loads of closed circulating irrigation system are small.
(4) Re-used fertilizer from drainage water to paddy fields is large in the order of closed, semi-open, and open types irrigation system. Particularly, re-used nitrogenous fertilizer of closed circulating irrigation system is very large.
3. Irrigation water and cultivation management for non-tilled and tilled paddy fields are examined in low-lying areas of the Tsugaru area and Hachiro-gata polder. Water requirement of. non-tilled paddy fields are smaller than tilled paddy fields during the under-water ploughing and rice-planting periods. Less