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The consistent gap between the irrigation service area and irrigated areas of national irrigation systems has been attributed to shortcomings either in design, technology, system operation, maintenance and management, policy, climate change, or a combination of these factors. Conventional rehabilitation, which mainly involves restoration of irrigation structures, has had little impact in closing this gap. This study examined the irrigation technology and water management techniques employed in two national irrigation systems. Its objectives were to identify technology constraints, cost-effective improvement practices and the potential for improving system performance with an end view of formulating a relevant modernization approach for national irrigation systems. The study used a logical design framework, field measurements and selected procedures of the Mapping System and Services for Canal Operation Techniques (MASSCOTE) as analytical tools. The findings show that inconsistencies among the design philosophy, system and operational objectives, flow control structures and water supply of the irrigation systems are root causes of their suboptimal performance. Careful consideration of the logical coherence among the selected irrigation technologies, water distribution techniques and water supply availability would form a crucial part of a relevant irrigation modernization planning for the case study systems and other irrigation systems in similar situations. (c) 2018 John Wiley & Sons, Ltd.