Irrigation water conveyance relies heavily on canal networks because they transport the water cheaply. However, water losses are high, which is a major concern in the face of soaring demand and dwindling new water sources. While researchers have investigated canal water losses and water loss types at irrigation scheme level, their variability and the main factors of influence at a global scale are still not clear. Thus, this study aims to elucidate the effects of canal water flow and soil characteristics on water losses globally. Data for 1388 canal reaches from 45 published articles are used. The results confirm that evaporation is so negligibly smaller than seepage and other water loss types that it can safely be ignored when analysing major water losses from canals. The study results also confirm that canal water losses decrease with soil clay content, due to decreasing permeability. The methods used for assessing water losses show significant influence on water losses; for example, the inflow–outflow method exhibits significantly higher water losses than the ponding technique. The current study results also show that canal shape, wetted perimeter and wetted area have a significant influence on water losses. It can be concluded from the study results that consideration of the physical mechanisms of water losses and different water loss types involved is important in future studies. It is recommended that future canal water loss studies, especially those focusing on losses via evaporation, also assess the effects of factors such as canal embankment height and depth of freeboard on the losses. These results are important for water scientists, engineers and practitioners.

中文翻译：

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基于对全球数据的荟萃分析回顾影响运河水损失的因素

灌溉输水严重依赖运河网络，因为它们运输水的成本很低。然而，水损失很高，这是在需求飙升和新水源减少的情况下的一个主要问题。虽然研究人员在灌溉计划层面调查了运河水损失和水损失类型，但它们在全球范围内的可变性和主要影响因素仍不清楚。因此，本研究旨在阐明运河水流和土壤特征对全球水分流失的影响。使用了来自 45 篇已发表文章的 1388 条运河河段的数据。结果证实，蒸发比渗流和其他水损失类型小得多，以至于在分析运河的主要水损失时可以安全地忽略它。研究结果还证实，由于渗透性降低，运河水量损失随着土壤粘土含量的增加而减少。用于评估水损失的方法对水损失有显着影响；例如，流入-流出法的水损失明显高于积水法。目前的研究结果还表明，运河形状、湿润周长和湿润面积对失水量有显着影响。从研究结果可以得出结论，考虑失水的物理机制和所涉及的不同失水类型在未来的研究中很重要。建议未来的运河失水研究，特别是那些关注蒸发损失的研究，也评估运河路堤高度和干舷深度等因素对损失的影响。