Water use for upland irrigation in a humid region of Japan

• Published in: Agricultural water management 1995, Vol.28 (3), p.185-200
• Main Authors: Yomota, Atsushi, Ndegwa, George M.
• Format: Article
• Language: English
• Subjects: ABSORCION DE AGUA; ABSORPTION D'EAU; Agricultural and forest climatology and meteorology. Irrigation. Drainage; Agronomy. Soil science and plant productions; Biological and medical sciences; Fundamental and applied biological sciences. Psychology; General agronomy. Plant production; IRRIGATION; Irrigation. Drainage; JAPAN; JAPON; LLUVIA; PLUIE; RAIN; RIEGO; Water; WATER UPTAKE
• ISSN: 0378-3774; 1873-2283
• DOI: 10.1016/0378-3774(95)01179-M

The situation of actual water use in a typical upland irrigation district was clarified through a study of irrigation quantity supplied to irrigators on a demand basis in Japan. Three methods were used to determine the district water use during periods with no rainfall. The first method considered this water use to be the maximum 10 days' average irrigation quantity in each month while the second method considered it to be the constant tetra in the relation between daily irrigation quantity and the moving average of daily rainfall. The third method considered this water use to be the constant term in the multiple linear regression of daily irrigation quantity and rainfall. All the methods gave almost the same results for the respective months analysed. This water use was about 1–2 mm day −1 which was very low when compared with the design irrigation quantity of 3.7–5.3 mm day −1 for the district. Effective rainfall was also determined. A land use survey in a representative sample area indicated that fallow fields occupied about 30% of the total irrigation area during the irrigation season. From the results of this study, it is recommended that the irrigation plan be based on an areal, e.g. district, water use instead of the present crop based consumptive use.