Abstract
This paper deals with the water consumption of a single paddy field and its seasonal and inter-annual variations during 1959-1968 in northern Japan. The values of water consumption items were measured by the “N” type gauge, the “Sato” type gauge, and the variable-head permeameter. The investigated years were grouped into three types on the basis of the standard deviations of the climatic condition, rice plant growth, and water requirement in depth: the high temperature year type, the normal temperature year type, and the low temperature year type.
The ten-year average value of evapotranspiration of Sendai, Miyagi Prefecture, was smaller than that of Kuroishi, Aomori Prefecture, which is located far north of Miyagi Prefecture. It may be roughly said that evapotranspiration and transpiration of the high temperature type years were about 20 percent larger than those of the normal temperature type years, and that those of the low temperature type years were about 10 percent smaller. As regards transpiration, its peak appeared differently according to the temperature year type.
Percolation through ridges was very large compared with vertical percolation under the root zone, and it showed seasonal and inter-annual variations.
