Greenhouse gas emissions from drainage ditches and irrigation canals

Drainage ditches and irrigation canals are widespread across the globe, and have a high potential to emit greenhouse gases (GHG) to the atmosphere, contributing to climate change. Often located in agricultural or urban areas, ditches may receive high inputs of organic matter and nutrients, thereby stimulating GHG production. Previous work (Peacock et al., 2021) has calculated the global magnitude of methane emissions from ditches (~1% of all anthropogenic methane emissions). However, the relative contributions of carbon dioxide and nitrous oxide remain unknown at national and global scales, although field studies show emissions of these GHGs can be large. As anthropogenic features, GHG emissions from ditches must be reported to the United Nations Framework Convention on Climate Change under Intergovernmental Panel on Climate Change (IPCC) protocols, but current guidelines only exist for methane (in the 2019 Refinement). Here, we present the results of an (ongoing) review where we collate existing scientific literature to synthesize carbon dioxide and nitrous oxide emissions data from ditches and canals around the world, as well as identifying the principle driving variables. The results of this research will help inform IPCC guidelines for improved GHG emission accounting, and reveal if ditches and canals act as hotspots of non-methane GHGs.