Abstract
The delivery water requirement, a component of water requirements for paddy irrigation, supposedly influences the discharge characteristics of irrigated paddy fields. Combined with the drainage from paddy fields, it forms part of the return flow, which will be utilized by downstream water users. A return flow analysis based on field surveys was applied to a 321 ha Okazeki Irrigation Project, Kokai River basin, Japan, where intermittent irrigation at 3-day intervals is practiced. A 10-hectare consolidated sub-area was chosen for the water distribution study. Tank model simulations showed that the runoff was affected by the existence of the delivery water requirement, which was determined as 20 percent of the total water requirements, according to field surveys.
