Determination of the Design Parameters of Water Distribution System for Paddy Rice Irrigation

A Case Study

Abstract

The irrigation water distribution system ensures the transport of water through field ditches to the irrigated fields while the field application system assures the transport of water within the fields. Therefore, in the design of water distribution, irrigation water distribution design parameters must be determined. This includes rice irrigation water requirement, irrigation stream size, and canal hydraulic design. The study therefore involves the selection of Irrigation method, determination of rice irrigation water requirement and irrigation control structures that regulate the discharge in each irrigation canal and ensure that each plot receives the required quantity of water at the correct time. By comparing irrigation water requirement for the three water requirement stages: flushing flow rate of 0.0015m³/s/ha, flooding water requirement of 0.0064m³/s/ha and maintenance water requirement of 0.0017m³/s/ha, the unit irrigation stream size is found to be governed by the flooding water requirement. A minimum flow rate of 0.007m³/s/ha was therefore considered adequate for unit irrigation. At 60% of the limiting opportunity time, the maximum allowable time to cover the basin with water is 7.32hr. This is used to obtain the minimum stream size of 0.01 m³/s required per 0.25 ha basin to achieve a plot irrigation efficiency of 80%. Natural ground slopes within the project area range from 0.3% to 0.6% resulting to two standard field layout patterns. The layout of flat land was adopted where the field shape is sufficiently regular and slope less than 0.4%.