Irrigation Systems

Abstract

Irrigation methods are classified into surface irrigation, sprinkler irrigation, and localized irrigation (drip/micro irrigation). Surface irrigation uses gravity: the water is distributed over the field as it infiltrates. With sprinkler irrigation, water is distributed across the field using pressurized pipes and sprinkled over the soil through nozzles. Drip/micro irrigation systems are conceived to localize the water to parts of the field and apply it frequently. The factors to be considered when selecting an irrigation method are: project goals (maximize economic return, minimize investment cost, conserving water and water quality), institutional and social site conditions (financial, labour availability, durability and robustness), physical site conditions (soil and topography). Irrigation performance assessment is advisable as part of the processes of operation improvement, and to establish system design criteria. The main irrigation performance indicators are irrigation efficiency, application efficiency, adequacy, and distribution uniformity. They assess different aspects of the irrigation process but have to be used jointly for a comprehensive assessment.