Abstract
This paper presents the results of the effect of hydro-meteorological factors' influence on irrigation water demand of rice fields, throughout the irrigation period, and additionally points out the subject, on building a forecasting system for irrigation water demand from the viewpoint of systematization of water management.
For this analysis, water management records were obtained from a study area, 1, 360 ha, located along the coast of Lake Biwa, and data of irrigation water demand was arranged on a daily basis. On the other hand, hydro-meteorological data was collected from the weather bureau in and around the study area.
Using these data, auto-correlation of daily irrigation water demand was analyzed, and then, the relationship between hydro-meteorological factors and irrigation water demand was clarified by multiple correlation analysis.
Moreover, for estimating the amount of daily average irrigation water demand, multiple regression function was studied by using hydro-meteorological factors.
Results obtained are as follows:
(1) Daily irrigation water demand does not show any peculiar auto-correlation throughout the irrigation period. However, within a day, it fluctuates due to the influence of water control by farmers in the field,
(2) Among the hydro-meteorological factors, the hours of sunshine, daily average temperature and daily rainfall especially have an influence on variations in daily average irrigation water demand throughout the irrigation period,
(3) Relationship between the above-mentioned factors and daily average irrigation water demand can be defined mathematically by a linear multiple regression equation,
(4) However, this equation does not always predict daily irrigation water demand, because fluctuations in irrigation water include factors originating from farm management practices, except for hydrometeorological factors, which can not be illustrated only by a mathematical model, such as the abovementioned equation,
(5) To forecast the irrigation water demand, a new model including the farm management practices needs to be developed.
