Review of factors affecting canal water losses based on a meta‐analysis of worldwide data

Abstract

AbstractIrrigation 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.