Water distribution uniformity and scheduling in micro-irrigation systems for water saving and environmental protection

Abstract

Micro-irrigation can apply water with high uniformity. However, uniformity alone is not sufficient to achieve the goal of irrigation. Irrigation scheduling is equally important in micro-irrigation systems. The significance of various irrigation schedules and emitter flow uniformities were examined in a system design. Several irrigation schedules were compared with an optimal irrigation schedule. The optimal irrigation schedule can achieve optimal return and also provide water saving compared with the conventional irrigation schedule in which the whole field is fully irrigated at the same time. Deep seepage can be eliminated or minimised by scheduling deficit irrigation. An environmental protection irrigation schedule, where the whole field is in deficit, can save more water but will cause some reduction in total return compared to the optimal irrigation schedule. A simple irrigation schedule, in which the total amount of water applied is the same as the amount required, cannot only produce nearly optimal yield but also achieve increased water saving when high uniformity is also applied in the design. It is important to specify that the differences in total return and water saving between different schedules are reduced when high uniformity is applied in the design. For high uniformity the effects of crop sensitivity to deficit irrigation are not important and result in only limited (or acceptable) yield reduction and over-irrigation. Since a high proportion of water resources are used for agricultural production, micro-irrigation systems designed with high uniformity can be scheduled to achieve water conservation as well as environmental protection.