Performance Evaluation of Drip Irrigation: A Case Study of Agri-parks in Gauteng Province, South Africa

The objective of the study was to assess the condition and performance efficiency of drip irrigation systems as part of a project that aimed to develop a WUE model for smallholder irrigation systems. This study was performed at four selected Agri-Parks in Gauteng province of South Africa, namely: Rooiwal, Soshanguve, Tarlton, and Westonaria. South African agriculture accounts for 62% of the national water demand. Almost 45% of the water is wasted through pollution and other losses. Consequently, irrigation systems are under pressure to improve their water-use efficiency (WUE). There is a paucity of information on WUE at smallholder irrigation schemes in the country, including at the Agri-Parks in Gauteng province due to many reasons that include a lack of simple tools that are friendly to mostly semi-literate irrigators. The Agri-Parks used in the study were irrigated using drip and microjet irrigation systems but the study focused on portions under drip systems. The condition and performance efficiency of the irrigation infrastructure were investigated. Field data collection took place from February to March 2021. Each irrigation system was divided into five components for convenience. Condition assessment was performed using a Condition Assessment Model (CAM) developed by ARC-NRE/AE, where enumerators visually observed the system component and assigned condition scores as guided by a template. The condition scores were uploaded into the CAM to generate condition indices (CI). Water conveyance efficiency (CE) and distribution uniformity (DU) were assessed on delivery and infield systems, respectively. CE was computed at the component level based on the inflow-outflow approach, while DU was computed based on measured emitter discharges. Overall, CI values ranged from 2.12-6.29, implying significant deterioration had occurred. The corresponding CE ranged 61-78% indicating water losses in the range 22-39%. On the other hand, DU was in the range of 60-95%, which was poor performance relative to expectations for drip irrigation systems. Overall, performance efficiency exhibited positive correlations with condition indices, pointing to possible opportunities for using condition state to predict the performance efficiency of drip irrigation system infrastructure, at least at the Agri-Parks in Gauteng province, South Africa. Nevertheless, further investigations covering a longer period, more locations and the role of maintenance are recommended. The role of non-physical parameters, e.g., management practices and choices, also needs further exploration.