Water-Saving Techniques and Practices for On-Farm Surface Irrigation Systems ^†

As surface irrigation systems are one of the most used water management techniques in the world, often working with high water losses, there is an urgency to their improvement. Modern methods that provide water savings and labour reduction require adequate design, management knowledge, and technical decision support. This study aims to improve water saving techniques for on-farm systems through an example of the decision-aid process being applied as a methodology based on the field experimentation and modelling of modern surface irrigation technologies in the Hetao (China) and Lower Mondego (Portugal) case studies. The performance indicators of irrigation water productivity (IWP) and the economic water productivity ratio (EWPR) were applied to compare the performance of several project solutions. The results obtained include a complete description of the latest irrigation solutions at the level basin, graded border, and graded furrows, which are adaptable to those case studies. The results revealed the benefits of a level-basin solution. For example, in Hetao, replacing the traditional system with a 100 m or 200 m long level basin, resulted in an increase in IWP by 40% and 3%, respectively, and in EWPR by 23% and 67%, respectively. The effect of a longer basin enables the reduction in operative costs, with a slight increase in distribution uniformity. In Lower Mondego, the IWP increased by 65% and the EWPR increased by 82%, by adopting graded furrows with 1.0‰ slopes and 200 m lengths. The main drivers of development of these surface irrigation systems were determined, namely, the runoff reuse and the system design and management. The issue that the local markets with equipment and consulting services should be available for farmers is also relevant to the development. It was proven that the effectiveness of modern surface water systems must adapt the solutions of the projects to the local characteristics of plot size and slope, soil type, and water supply.